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  • ddc:550  (50)
  • ddc:523  (15)
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  • English  (74)
  • German
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  • 2020-2023  (74)
  • 1975-1979
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  • English  (74)
  • German
  • Polish
  • German  (46)
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  • 1
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    Simulating Linear Kinematic Features in Viscous‐Plastic Sea Ice Models on Quadrilateral and Triangular Grids With Different Variable Staggering (2021)
    Details
    Publication Date: 2022-04-04
    Description: Observations in polar regions show that sea ice deformations are often narrow linear features. These long bands of deformations are referred to as Linear Kinematic Features (LKFs). Viscous‐plastic sea ice models have the capability to simulate LKFs and more generally sea ice deformations. Moreover, viscous‐plastic models simulate a larger number and more refined LKFs as the spatial resolution is increased. Besides grid spacing, other aspects of a numerical implementation, such as the placement of velocities and the associated degrees of freedom, may impact the formation of simulated LKFs. To explore these effects this study compares numerical solutions of sea ice models with different velocity staggering in a benchmark problem. Discretizations based on A‐,B‐, and C‐grid systems on quadrilateral meshes have similar resolution properties as an approximation with an A‐grid staggering on triangular grids (with the same total number of vertices). CD‐grid approximations with a given grid spacing have properties, specifically the number and length of simulated LKFs, that are qualitatively similar to approximations on conventional Arakawa A‐grid, B‐grid, and C‐grid approaches with half the grid spacing or less, making the CD‐discretization more efficient with respect to grid resolution. One reason for this behavior is the fact that the CD‐grid approach has a higher number of degrees of freedom to discretize the velocity field. The higher effective resolution of the CD‐discretization makes it an attractive alternative to conventional discretizations.
    Description: Plain Language Summary: Sea ice in the Arctic and Antarctic Oceans plays an important role in the exchange of heat and freshwater between the atmosphere and the ocean and hence in the climate in general. Satellite observations of polar regions show that the ice drift sometimes produces long features that are either cracks (leads) and zones of thicker sea ice (pressure ridges). This phenomenon is called deformation. It is mathematically described by the non‐uniform way in which the ice moves. For numerical models of sea ice motion it is difficult to represent this deformation accurately. Details of the numerics may affect the way these models simulate leads and ridges, their number and length. Specifically, we find by comparing different numerical models, that the way the model variables are ordered on a computational grid to solve the mathematical equations of sea ice motion has an effect of how many deformation features can be represented on a grid with a given spacing between grid points. A new discretization (ordering of model variables) turns out to resolve more details of the approximated field than traditional methods.
    Description: Key Points: The placement of the sea ice velocity has a mayor influence on the number of simulated linear kinematic features (LKFs). The CD‐grid resolves twice as many LKFs compared to A, B, C‐grids. A, B, C‐grids on quadrilateral meshes resolve a similar number of LKFs as A‐grids on triangular meshes (with the same total number of nodes).
    Keywords: ddc:550 ; ddc:551.343
    Language: English
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  • 2
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    Spatial variability in river bed porosity determined by nuclear density gauging: A case study from a French gravel‐bed river (2021)
    Details
    Publication Date: 2022-04-01
    Description: Porosity is one of the key properties of fluvial sediments. It is defined as the ratio of pore volume to total volume. In river science, porosity is often assumed to be spatially constant, which might be a gross simplification of reality. Ignoring the spatial variations in porosity can cause errors in morphological, ecological, hydrological, hydrogeological and sedimentological applications. Although detailed information about spatial porosity variations can be obtained from porosity measurements at field sites, such information has never been collected where these variations might be important. In this study, field porosity measurements were carried out to quantify the magnitude of the spatial porosity variation for four different sedimentological environments of a braided river: a confluence, a tributary delta, a braid bar and a secondary channel. A nuclear density gauge was used for the measurement of porosity. The nuclear density gauge proved to be a time‐saving and labour‐saving technique that produces accurate porosity values with a root mean square error of 0.03. The four sedimentological environments showed significant differences in porosity, with mean porosity being lower for confluence and bar than for delta and secondary channel. Semi‐variogram analysis showed the absence of any spatial correlation in porosity for distances beyond 4 m. This shows that distance cannot be used as a parameter for porosity extrapolation in a fluvial system unless the extrapolation distance is less than 4 m. At least eight measurements of porosity are required to obtain a reliable estimate of mean porosity in a sedimentary environment, i.e. with uncertainty 〈0.03. Although grain size characteristics were found to have a significant impact on porosity, the relationships between these parameters and porosity were not very strong in this study. The unique porosity dataset, presented in this article, provides a valuable source of information for researchers and river managers.
    Description: Deutsche Forschungsgemeinschaft
    Keywords: ddc:550
    Language: English
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  • 3
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    Joint Inversion of Receiver Functions and Apparent Incidence Angles for Sparse Seismic Data (2021)
    Details
    Publication Date: 2022-03-30
    Description: The estimation of crustal structure and thickness is essential in understanding the formation and evolution of terrestrial planets. Initial planetary missions with seismic instrumentation on board face the additional challenge of dealing with seismic activity levels that are only poorly constrained a priori. For example, the lack of plate tectonics on Mars leads to low seismicity, which could, in turn, hinder the application of many terrestrial data analysis techniques. Here we propose using a joint inversion of receiver functions and apparent incidence angles, which contain information on absolute S‐wave velocities of the subsurface. Since receiver function inversions suffer from a velocity depth trade‐off, we in addition exploit a simple relation that defines apparent S‐wave velocity as a function of observed apparent P‐wave incidence angles to constrain the parameter space. We then use the Neighborhood Algorithm for the inversion of a suitable joint objective function. The resulting ensemble of models is then used to derive uncertainty estimates for each model parameter. In preparation for the analysis of data from the InSight mission, we show the application of our proposed method on Mars synthetics and sparse terrestrial data sets from different geological settings using both single and multiple events. We use information‐theoretic statistical tests as model selection criteria and discuss their relevance and implications in a seismological framework.
    Description: Key Points: We propose the joint inversion of receiver functions and apparent S‐wave velocity curves to estimate crustal thickness. Using the Neighborhood Algorithm, we show how a full uncertainty estimate can be computed from an ensemble solution. The method is applied to Martian synthetics and terrestrial data sets comprising single and multiple events.
    Description: IMPRS
    Description: Emeritus group
    Description: DLR German Space Agency
    Description: http://www.orfeus-eu.org/data/eida/
    Description: http://instaseis.ethz.ch/marssynthetics/
    Keywords: ddc:622.1592 ; ddc:523
    Language: English
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  • 4
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    Tracking Downstream Variability in Large Grain‐Size Distributions in the South‐Central Andes (2021)
    Details
    Publication Date: 2022-03-31
    Description: Mixed sand‐ and gravel‐bed rivers record erosion, transport, and fining signals in their bedload size distributions. Thus, grain‐size data are imperative for studying these processes. However, collecting hundreds to thousands of pebble measurements in steep and dynamic high‐mountain river settings remains challenging. Using the recently published digital grain‐sizing algorithm PebbleCounts, we were able to survey seven large (≥ 1,000 m2) channel cross‐sections and measure thousands to tens‐of‐thousands of grains per survey along a 100‐km stretch of the trunk stream of the Toro Basin in Northwest Argentina. The study region traverses a steep topographic and environmental gradient on the eastern margin of the Central Andean Plateau. Careful counting and validation allows us to identify measurement errors and constrain percentile uncertainties using large sample sizes. In the coarse ≥2.5 cm fraction of bedload, only the uppermost size percentiles (≥95th) vary significantly downstream, whereas the 50th and 84th percentiles show less variability. We note a relation between increases in these upper percentiles and along‐channel junctions with large, steep tributaries. This signal is strongly influenced by lithology and geologic structures, and mixed with local hillslope input. In steep catchments like the Toro Basin, we suggest nonlinear relationships between geomorphic metrics and grain size, whereby the steepest parts of the landscape exert primary control on the upper grain‐size percentiles. Thus, average or median metrics that do not apply weights or thresholds to steeper topography may be less predictive of grain‐size distributions in such settings.
    Description: Plain Language Summary: Rock fragments on hillsides are transported to rivers, eventually becoming pebbles, sand, and mud as they are carried downstream by flowing water. The initial size of the pebbles, the way the size changes downstream, and the overprinting of the sizes with new pebbles from other hills and tributaries all form a complex process that can be difficult to disentangle. Yet studying the size of the pebbles at a given stream location or in a sedimentary deposit can provide insights into the conditions of their transport in terms of local upstream patterns of erosion, tectonics, and climate. We show that just looking at the size of the large pebbles on a riverbed can be used to infer the sources of material, but, since there are fewer large pebbles, they require more measurements to quantify. This necessitates new methods for pebble measurement using modern image‐processing tools.
    Description: Key Points: Complex grain‐size distributions in dynamic mountain rivers can be computed via thousands of measurements from PebbleCounts. Many measurements allow robust estimation of higher percentiles and we observe the most significant changes in the ≥95th percentile. Downstream grain‐size variation is nonlinearly related to variations in topographic steepness and lithology.
    Description: Deutsches Zentrum für Luft‐ und Raumfahrt (DLR) http://dx.doi.org/10.13039/501100002946
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347
    Description: Brandenburger Staatsministerium für Wissenschaft, Forschung und Kultur (MWFK) http://dx.doi.org/10.13039/501100004581
    Description: https://zenodo.org/record/5089789
    Keywords: ddc:551.3 ; ddc:550
    Language: English
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  • 5
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    Paleoclimate Evolution on Titan After Episodic Massive Methane Outgassing Simulated by a Global Climate Model (2021)
    Details
    Publication Date: 2022-03-25
    Description: Titan's paleoclimate after the onset of the putative last major methane outgassing event 700 Myr ago is simulated by a global climate model. If the atmosphere was methane‐depleted prior to outgassing, outgassed methane initially causes warming due to increased greenhouse effect. Further outgassing leads to methane snowfall, which in turn cools the troposphere and surface by an ice‐albedo feedback and thereby initiates a lengthy ice age. Formation of ice sheets begins in the polar region, but with increasing methane inventory the entire globe is eventually covered by surface methane frost as thick as 100 m, with local accumulation on elevated terrains. Among various time‐dependent input parameters the methane inventory by far exerts the greatest control over the climate evolution. As Titan's climate transitions from a dry state via a partially ice‐covered state to a globally ice‐covered state, the circulation and precipitation pattern change profoundly and the tropospheric temperature further decreases. Globally ice‐covered snowball Titan is characterized by weak meridional circulation, weak seasonality and widespread snowfall. Frost ablation begins after the end of outgassing due to photochemical destruction of atmospheric methane. It is conceivable that Titan's polar seas resulted from melting of the polar caps within the past 10 Myr and subsequent drainage to the polar basins. Surface methane frost could only melt when the frost retreated to the polar region, which led to global warming by lowering of the surface albedo at low latitudes and increased greenhouse effect.
    Description: Plain Language Summary: Saturn's moon Titan may have experienced long periods of cold climate in the past when the nitrogen atmosphere contained no methane unlike the present atmosphere. We simulated how Titan's climate may have changed when large amounts of methane were outgassed into such a cold atmosphere as indicated by models of Titan's evolution. The atmosphere can hold a certain amount of methane but the vast majority of outgassed methane condenses out as snow and is deposited on the surface. Bright methane snow on the surface keeps the surface cold and thereby prevents efficient greenhouse warming. Initially, surface methane frost is confined to high latitudes, but eventually the entire globe will be ice‐covered under the assumed total amount of outgassed methane. The seasonal and global pattern of atmospheric circulation and snowfall strongly depend on the degree of frost coverage. The surface frost sublimes away long after outgassing has ceased because methane is destroyed in the atmosphere by photochemistry. Eventually, the polar caps melt, leaving behind the observed polar seas.
    Description: Key Points: Massive methane outgassing into Titan's atmosphere should have caused global ice sheets if the atmosphere was previously depleted in methane. Climate of methane snowball Titan is characterized by weak circulation, low temperature, weak seasonality and widespread snowfall. Melting polar caps in geologically recent past may have resulted in polar seas.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:523 ; ddc:551.5
    Language: English
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  • 6
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    Temperatures Near the Lunar Poles and Their Correlation With Hydrogen Predicted by LEND (2021)
    Details
    Publication Date: 2022-03-24
    Description: The lunar polar regions offer permanently shadowed regions (PSRs) representing the only regions which are cold enough for water ice to accumulate on the surface. The Lunar Exploration Neutron Detector (LEND) aboard the Lunar Reconnaissance Orbiter (LRO) has mapped the polar regions for their hydrogen abundance which possibly resides there in the form of water ice. Neutron suppression regions (NSRs) are regions of excessive hydrogen concentrations and were previously identified using LEND data. At each pole, we applied thermal modeling to three NSRs and one unclassified region to evaluate the correlation between hydrogen concentrations and temperatures. Our thermal model delivers temperature estimates for the surface and for 29 layers in the sub‐surface down to 2 m depth. We compared our temperature maps at each layer to LEND neutron suppression maps to reveal the range of depths at which both maps correlate best. As anticipated, we find the three south polar NSRs which are coincident with PSRs in agreement with respective (near)‐surface temperatures that support the accumulation of water ice. Water ice is suspected to be present in the upper ≈19 cm layer of regolith. The three north polar NSRs however lie in non‐PSR areas and are counter‐intuitive as such that most surfaces reach temperatures that are too high for water ice to exist. However, we find that temperatures are cold enough in the shallow sub‐surface and suggest water ice to be present at depths down to ≈35–65 cm. Additionally we find ideal conditions for ice pumping into the sub‐surface at the north polar NSRs. The reported depths are observable by LEND and can, at least in part, explain the existence and shape of the observed hydrogen signal. Although we can substantiate the anticipated correlation between hydrogen abundance and temperature the converse argument cannot be made.
    Description: Plain Language Summary: The lunar poles have quite unique illumination conditions. For instance, the Sun never shines on some crater floors. As a consequence, the floors of those craters are very cold and dark. Here, water ice can accumulate on the surface and can be preserved for long periods of time. One of the instruments mounted on the Moon‐orbiting satellite Lunar Reconnaissance Orbiter is capable of detecting areas where hydrogen is located, which is assumed to be present in the form of water ice. For instance, the instrument detected several areas at the lunar poles where a lot more water ice is found than at other locations. For these special locations, we calculated the temperatures at the surface and near sub‐surface to see whether they are indeed cold enough for water to freeze. At some of these locations, surface temperatures turn out to be too warm. However, we found that at these warm surfaces where no water ice can exist it can be transported into the sub‐surface and survive there. This mechanism is referred to as ice pumping. In summary, we could show that temperatures at all these special locations are usually cold enough for water ice, either right at the surface or within the first meter of soil.
    Description: Key Points: Some neutron suppression regions (NSRs) form from surface ice deposits while others may form through ice pumping in the sub‐surface. NSRs identified by Lunar Exploration Neutron Detector correlate well with low surface temperatures in permanently shadowed regions (PSRs) and are in agreement with sub‐surface temperatures in non‐PSR.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:523 ; ddc:551.5
    Language: English
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  • 7
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    Directionality of the Martian Surface Radiation and Derivation of the Upward Albedo Radiation (2021)
    Details
    Publication Date: 2022-03-24
    Description: Since 2012 August, the Radiation Assessment Detector (RAD) on the Curiosity rover has been characterizing the Martian surface radiation field which is essential in preparation for future crewed Mars missions. RAD observed radiation dose is influenced by variable topographical features as the rover traverses through the terrain. In particular, while Curiosity was parked near a butte in the Murray Buttes area, we find a decrease of the dose rate by (5 ± 1)% as 19% of the sky was obstructed, versus 10% in an average reference period. Combining a zenith‐angle‐dependent radiation model and the rover panoramic visibility map leads to a predicted reduction of the downward dose by ∼12% due to the obstruction, larger than the observed decrease. With the hypothesis that this difference is attributable to albedo radiation coming from the butte, we estimate the (flat‐terrain) albedo radiation to be about 19% of the total surface dose.
    Description: Plain Language Summary: Interplanetary space is filled with energetic particles that can affect the health of astronauts, for example, by causing late‐arising cancer and possibly hereditary diseases. Mars lacks a global magnetic field and its atmosphere is very thin compared to Earth's. Thus its surface is exposed to such space radiation which presents risks to future humans on Mars. Mitigation strategies could include using natural geological structures on Mars, for example, cave skylights and lava tubes and even simple buttes, for protection. The Radiation Assessment Detector (RAD) on the Curiosity rover has observed a decrease of the radiation absorbed dose rate by (5 ± 1)% while Curiosity was parked near a butte. This provides the first direct illustration that Mars's surface features may serve as potential radiation shelters for future missions. However, when exploiting such shielding possibilities, the secondary radiation generated in the terrain of Mars that is, emitted backwards must also be considered. Combining the RAD observation with a radiation transport model, we derive such “reflected” radiation dose on a flat terrain to be about 19% of the total surface dose.
    Description: Key Points: The Martian surface radiation is influenced by topographical features. The surface downward radiation dose of particles traversing through the atmosphere depends on the zenith angle. The surface upward radiation dose is about 19% of the total dose.
    Description: Strategic Priority Program of CAS
    Description: NSFC
    Description: CNSA pre‐research project on civil aerospace technologies
    Description: NASA, Jet Propulsion Laboratory (JPL) http://dx.doi.org/10.13039/100006196
    Description: Deutsches Zentrum für Luft‐und Raumfahrt (DLR) http://dx.doi.org/10.13039/501100002946
    Keywords: ddc:523
    Language: English
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  • 8
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    Faulting and Magmatic Accretion Across the Overlapping Spreading Center Between Vance Segment and Axial South Rift, Juan de Fuca Ridge (2022)
    Details
    Publication Date: 2022-03-24
    Description: Plate divergence along mid‐ocean ridges is accommodated through faulting and magmatic accretion, and, at overlapping spreading centers (OSC), is distributed across two curvilinear overlapping ridge axes. One‐meter resolution bathymetry acquired by autonomous underwater vehicles, combined with distribution and ages of lava flows, is used to: (a) analyze the spatial and temporal distribution of flows, faults, and fissures in the OSC between the distal south rift zone of Axial Seamount and the Vance Segment, (b) locate spreading axes, (c) calculate extension, and (d) determine the proportion of extension accommodated at the surface by faults and fissures versus volcanic extrusion over a period of ∼1300–1450 years. Our study reveals that in the recent history of the ridges, extension over a distance of 14 km across the Axial/Vance OSC was asymmetric in proportion and style: faults and fissures across 1–2 km of the Vance axial valley accommodated ∼3/4 of the spreading, whereas dike‐fed eruptions contributed ∼1/4 of the extension and occurred across 4 km of the south rift of Axial Seamount.
    Description: Plain Language Summary: Along mid‐ocean ridges, oceanic plates separate through the formation and growth of faults and the emplacement of dikes supplying lava flows. Where segments overlap in a zone of separation, these processes are distributed along two spreading axes separated by 2–30 km kilometers. We combine 1‐m resolution bathymetry collected by autonomous underwater vehicles and the age of large lava flows to (a) analyze the distribution of faults and lava flows where Axial Seamount overlaps with the Vance Segment, (b) define the current plate boundary, (c) calculate the speed of plate separation, and (d) determine the proportion and locations of fault extension versus flow emplacement. Our study shows that during the last ∼1300–1450 years, fault formation and growth along the Vance Segment are the main contributor to plate separation. In contrast, the emplacement of dikes and lava flows along Axial Seamount account only for ∼1/4 of the plate separation.
    Description: Key Points: Autonomous underwater vehicle mapping of an overlapping spreading center reveals the proportion of faulting and eruptions that occurred during the last ∼1300–1450 years. Faulting at the Vance Segment accommodates ∼3/4 of the spreading and magmatic accretion along Axial Seamount south rift accounts for ∼1/4. The spreading axis is 〈250 m wide along the Vance Segment but ∼4 km wide along the south rift of Axial Seamount.
    Description: David and Lucile Packard Foundation (PF) http://dx.doi.org/10.13039/100000008
    Keywords: ddc:551.8 ; ddc:551.13
    Language: English
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  • 9
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    Induced Magnetic Fields and Plasma Motions in the Inner Part of the Martian Magnetosphere (2021)
    Details
    Publication Date: 2022-03-24
    Description: Analysis of Mars Atmosphere and Volatile Evolution (MAVEN)/Supra‐Thermal And Thermal Ion Composition observations in the Martian upper atmosphere, bounded at higher altitudes by the shocked solar wind, shows that the draping of interplanetary magnetic field penetrates down to low altitudes (∼200−250 km) and governs dynamics of the ionosphere. The upper ionospheric plasma is driven into motion flowing around Mars similar to the shocked solar wind in the adjacent magnetosheath. Such a fluid‐like motion is accompanied by ion acceleration caused by the bending of the magnetic field, leading to ion extraction and finally to ion pickup. Extraction of ions and their acceleration produces a recoil effect of the bulk ionosphere in the opposite direction. This provides a strong asymmetry in ion dynamics in two different hemispheres, accompanied by wrapping of the magnetic field lines around Mars and respective reconnection.
    Description: Plain Language Summary: Although the Martian magnetosphere is hybrid and contains components of the induced and intrinsic magnetosphere, is possible to display these components by using the specific coordinate systems. Here we study the properties of the induced magnetosphere using the data obtained by MAVEN spacecraft. The interplanetary magnetic field penetrates deep into the Martian ionosphere draping around Mars and drive to the motion dense ionospheric plasma. Draping features and the induced plasma motions occur different in two hemispheres determined by the direction of the motional electric field in the solar wind. Ion acceleration and extraction is accompanied by a recoil effect that leads to a shift and asymmetry of the ionosphere.
    Description: Key Points: Draping of the interplanetary magnetic field around Mars penetrates deep to the ionosphere enveloping the planet and driving the ionosphere to the bulk motion. Draping and motion of the ionospheric plasma is characterized by asymmetry by the direction of the motional electric field in solar wind. Ion acceleration and extraction from the ionosphere is accompanied by a shift of the bulk ionosphere in the opposite direction.
    Description: National Aeronautics and Space Administration http://dx.doi.org/10.13039/100000104
    Description: DFG http://dx.doi.org/10.13039/501100001659
    Description: Russian Science Foundation http://dx.doi.org/10.13039/501100006769
    Keywords: ddc:523 ; ddc:551.5
    Language: English
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  • 10
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    Impact of Late Cretaceous inversion and Cenozoic extension on salt structure growth in the Baltic sector of the North German Basin (2021)
    Details
    Publication Date: 2022-03-24
    Description: The Late Cretaceous to Cenozoic is known for its multiple inversion events, which affected Central Europe's intracontinental sedimentary basins. Based on a 2D seismic profile network imaging the basin fill without gaps from the base Zechstein to the seafloor, we investigate the nature and impact of these inversion events on Zechstein salt structures in the Baltic sector of the North German Basin. These insights improve the understanding of salt structure evolution in the region and are of interest for any type of subsurface usage. We link stratigraphic interpretation to previous studies and nearby wells and present key seismic depth sections and thickness maps with a new stratigraphic subdivision for the Upper Cretaceous and Cenozoic covering the eastern Glückstadt Graben and the Bays of Kiel and Mecklenburg. Time‐depth conversion is based on velocity information derived from refraction travel‐time tomography. Our results show that minor salt movement in the eastern Glückstadt Graben and in the Bay of Mecklenburg started contemporaneous with Late Cretaceous inversion in the Coniacian‐Santonian. Minor salt movement continued until the end of the Late Cretaceous. Overlying upper Paleocene and lower Eocene deposits show constant thickness without indications for salt movement suggesting a phase of tectonic quiescence from the late Paleocene to middle Eocene. In the late Eocene to Oligocene, major salt movement recommenced in the eastern Glückstadt Graben. In the Bays of Kiel and Mecklenburg, late Neogene uplift removed much of the Eocene‐Miocene succession. Preserved deposits indicate major post‐middle Eocene salt movement, which likely occurred coeval with the revived activity in the Glückstadt Graben. Cenozoic salt structure growth critically exceeded salt flow during Late Cretaceous inversion. Cenozoic salt movement could have been triggered by Alpine/Pyrenean‐controlled thin‐skinned compression, but is more likely controlled by thin‐skinned extension, possibly related to the beginning development of the European Cenozoic Rift System.
    Description: In the Baltic sector of the North German Basin, minor salt movement started comremporaneous with Late Cretaceous inversion in the Coniacian‐Santonian and lasted until the end of the Late Cretaceous. A late Paleocene to middle Eocene phase of tectonic quiescense was followed by recommencing major salt movement in the Glückstadt Graben in the Late Eocene‐Oligocene. This Cenozoic phase of salt structure growth critically exceeded salt flow during the Late Cretaceous inversion and is likely controlled by thin‐skinned extension, possibly related to the beginning development of the European Cenozoic Rift System.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.8 ; ddc:554.3
    Language: English
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  • 11
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    3D Active Source Seismic Imaging of the Alpine Fault Zone and the Whataroa Glacial Valley in New Zealand (2021)
    Details
    Publication Date: 2022-03-24
    Description: The Alpine Fault zone in New Zealand marks a major transpressional plate boundary that is late in its typical earthquake cycle. Understanding the subsurface structures is crucial to understand the tectonic processes taking place. A unique seismic survey including 2D lines, a 3D array, and borehole recordings, has been performed in the Whataroa Valley and provides new insights into the Alpine Fault zone down to ∼2 km depth at the location of the Deep Fault Drilling Project (DFDP)‐2 drill site. Seismic images are obtained by focusing prestack depth migration approaches. Despite the challenging conditions for seismic imaging within a sediment filled glacial valley and steeply dipping valley flanks, several structures related to the valley itself as well as the tectonic fault system are imaged. A set of several reflectors dipping 40°–56° to the southeast are identified in a ∼600 m wide zone that is interpreted to be the minimum extent of the damage zone. Different approaches image one distinct reflector dipping at ∼40°, which is interpreted to be the main Alpine Fault reflector located only ∼100 m beneath the maximum drilled depth of the DFDP‐2B borehole. At shallower depths (z 〈 0.5 km), additional reflectors are identified as fault segments with generally steeper dips up to 56°. Additionally, a glacially over‐deepened trough with nearly horizontally layered sediments and a major fault (z 〈 0.5 km) are identified 0.5–1 km south of the DFDP‐2B borehole. Thus, a complex structural environment is seismically imaged and shows the complexity of the Alpine Fault at Whataroa.
    Description: Plain Language Summary: The Alpine Fault in New Zealand is a major plate boundary, where a large earthquake will likely occur in the near future. Thus, it is important to understanding the detailed processes of how and where such an earthquake occurs. Many scientists are involved in this work, particularly in the attempt of drilling through the fault zone with a ∼900 m deep borehole. We analyzed new seismic data from this area using sensors in the borehole and at the surface to record small ground movements caused by a vibrating surface source causing waves that travel through the ground. From these data, we obtained a detailed image of the structures in the subsurface, for the first time in 3D, by applying advanced analysis methods. Hence, we can better understand the shape of the glacial valley and of the fault zone, that is, the local structures of the continental plate boundary. We interpret at least 600 m wide zone of disturbed rocks and identify a potential major fractured plane down to about 1 km depth. Our studies may help to understand structures that host earthquakes in this area.
    Description: Key Points: We use focusing prestack depth migration with detailed seismic data to analyze the complex subsurface environment of the Alpine Fault zone. Seismic images show Alpine Fault zone related reflectors at a depth of ∼0.2–1 km dipping ∼40°–56° around the DFDP‐2B borehole. Complex structures within the glacial Whataroa Valley are imaged showing steep valley flanks, faults, and internal sedimentary horizons.
    Description: German Research Foundation (DFG)
    Description: Earthquake Commission (EQC) http://dx.doi.org/10.13039/100012181
    Description: NSERC discovery and Canada Research Chairs Program
    Description: Canadian Foundation for Innovation
    Keywords: ddc:622.1592 ; ddc:551.8
    Language: English
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    Rheological and Mechanical Layering of the Crust Underneath Thumbprint Terrains in Arcadia Planitia, Mars (2021)
    Details
    Publication Date: 2022-03-28
    Description: In the area of Arcadia Planitia in the Northern hemisphere of Mars, mounds indicating fluid and sediment emissions have been already recognized. Here, we show that through fractal and fracture‐spacing analyses of a large vent population it is possible to infer the mechanical layering of the underlying subsurface. Our work includes the mapping of an entire population of 9,028 vents over an area of 122,000 km2. The analysis of mound distribution at the surface led to the formulation of inferences about the subsurface feeding conduits, and to the identification of three mechanical discontinuities at c. 4–5, c. 14–23, and c. 50–55 km. This evidence matches the mechanical stratigraphy recorded by the InSight NASA mission, and is in agreement with independent previous subsurface global modeling, supporting our conclusions.
    Description: Plain Language Summary: The Martian northern hemisphere displays mounds interpreted to be the result of sediment and water erupting onto the surface. We analyzed the mounds spatial distribution and found patterns that reflects the extent at depth of the subsurface conduits that fed those mounds (array of fractures, i.e., high permeability pathways) allowing the sediment and water upwelling. These conduits thus connect the surface to the source of the erupted materials at depth. These source levels are located at the base of layers characterized by mechanical properties different from the adjacent ones (e.g., loose sediments vs. crystalline bedrock). Such layers are hence referred as mechanical discontinuities. We identified three discontinuities: at c. 4–5, c. 14–23, and c. 50–55 km. Our outcomes match the mechanical stratigraphy recorded by the InSight NASA mission, and is in agreement with independent previous subsurface global modeling, supporting our conclusions.
    Description: Key Points: We present a complete mapping of a large vent population in the Arcadia Planitia region of the northern plains of Mars. We reconstructed the subsurface mechanical layering underlying the vent field using spatial distribution analysis. These analyses proved to be efficient and open the possibility of collecting subsurface rheological data from areas beyond InSight reach.
    Description: H2020 Excellent Science (H2020 Priority Excellent Science) http://dx.doi.org/10.13039/100010662
    Description: DLR Management Board Young Research Group Leader Program
    Description: Executive Board Member for Space Research and Technology
    Keywords: ddc:523
    Language: English
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    Late Pleistocene‐Holocene Slip Rates in the Northwestern Zagros Mountains (Kurdistan Region of Iraq) Derived From Luminescence Dating of River Terraces and Structural Modeling (2021)
    Details
    Publication Date: 2022-03-23
    Description: A significant amount of the ongoing shortening between the Eurasian and Arabian plates is accommodated within the Zagros Fold‐Thrust Belt. However, the spatial and temporal distribution of active shortening within the belt, especially in its NW part, is not yet well constrained. We determined depositional ages of uplifted river terraces crossing the belt along the Greater Zab River using luminescence dating. Kinematic modeling of the fault‐related fold belt was then used to calculate long‐term slip rates during the Late Pleistocene to Holocene. Our results provide new insight into the rates of active faulting and folding in the area. The Zagros Mountain Front Fault accommodates about 1.46 ± 0.60 mm a−1 of slip, while a more external basement fault further to the SW accommodates less than 0.41 ± 0.16 mm a−1. Horizontal slip rates related to detachment folding of two anticlines within the Zagros Foothills are 0.40 ± 0.10 and 1.24 ± 0.36 mm a−1. Basement thrusting and thickening of the crust are restricted to the NE part of the Zagros belt. This is also reflected in the regional topography and in the distribution of uplifted terraces. In the southwestern part, the deformation is limited mainly to folding and thrusting of the sedimentary cover above a Triassic basal detachment. In the NE, deformation is associated with slip on basement thrusts. Our study sheds light on the distribution of shortening in the Zagros Mountains and helps to understand the regional tectonic system. Our results may be the foundation for a better seismic hazard assessment of the entire area.
    Description: Plain Language Summary: In active mountain belts, river terraces found above the present‐day river level can be indicative of differences in uplift rates due to the thickening, faulting, and folding processes in the Earth's crust. These processes, driven by the motion of tectonic plates, are responsible for the formation of mountain belts. Here, we took sediment samples from uplifted river terraces along the Greater Zab River that crosses the Zagros Mountains in the Kurdistan Region of Iraq. We determined their deposition age using luminescence dating. From their age and elevation, we calculated uplift rates. We built a geometrical model of the fault zones in the area and determined how fast the slip occurs on these faults based on the uplift rates. Our results indicate that there were less than two millimeter per year of slip on these faults on average during the last 60 thousand years. This motion is a result of the convergence between the Arabian and Eurasian plates. With studies like this we can measure how fast fault blocks move, even if they were not associated with large earthquakes in the recent past. This approach helps to better assess the potential earthquake hazard in the area under investigation.
    Description: Key Points: We estimated fault slip rates in the NW Zagros Mountains by luminescence dating of river terraces and structural modeling. There is c. 1.46 mm a−1 slip on the Mountain Front Fault and c. 1.64 mm a−1 slip from detachment folding in the NE part of the Foothill Zone. Crustal thickening and basement thrusting occur in the NE parts of the Foothill Zone and only cover deformation occur in the SW parts.
    Description: German Academic Exchange Service (DAAD) http://dx.doi.org/10.13039/501100001655
    Description: German Research Foundation (DFG) http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:551.8
    Language: English
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    Formation of the Thebe Extension in the Ring System of Jupiter (2021)
    Details
    Publication Date: 2022-03-29
    Description: Jupiter's tenuous dust ring system is embedded in the planet's inner magnetosphere, and—among other structures—contains a very tenuous protrusion called the Thebe extension. In an attempt to explain the existence of this swath of particles beyond Thebe's orbit, Hamilton and Krüger (2008), https://doi.org/10.1038/nature06886 proposed that the dust particle motion is driven by a shadow resonance caused by variable dust charging on the day and night side of Jupiter. However, the model by Divine and Garrett (1983), https://doi.org/10.1029/ja088ia09p06889 together with recent observations by the Juno spacecraft indicates a warm and rather dense inner magnetosphere of Jupiter which implies that the mechanism of the shadow resonance does not work. Instead, we argue that dust grains ejected from Thebe due to micrometeoroid bombardment become the source of dust in the Thebe extension. We show that large (grain radii of a few micrometers up to multi‐micrometers) charged dust grains having significant initial velocities oscillate in the Thebe extension. Smaller charged grains (with sub‐micrometer radii) ejected from Thebe do not spend much time in the Thebe extension and migrate into the Thebe ring. At the same time, if such grains are ejected from larger dust grains in the Thebe extension due to fragmentation, they continue to oscillate within the Thebe extension for years. We argue that fragmentation of large dust grains in the Thebe extensions could be the main source of sub‐micrometer grains detected in the Thebe extension.
    Description: Key Points: In Jupiter's warm and dense inner magnetosphere dust grains acquire high negative electric charges. Dust particles ejected from Thebe with sufficient speeds contribute to the formation of the Thebe extension. Instead of shadow resonances as suggested earlier an alternative mechanism is suggested for the formation of the Thebe extension.
    Description: Max Planck Institute for Solar System Research
    Keywords: ddc:523
    Language: English
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    Global Drivers and Transport Mechanisms of Lunar Rockfalls (2021)
    Details
    Publication Date: 2022-03-29
    Description: The long‐ and short‐term drivers and transport mechanisms of lunar rockfalls are currently not well understood, but could provide valuable information about the geologic processes that still shape the surface of the Moon today. Here, we compare the global distribution of rockfalls with relevant geophysical data, such as seismic, topographic, thermal, gravity anomaly, and tidal displacement data sets. Rockfalls appear to predominantly occur (a) on equator‐facing slopes and thus in regions with large thermal amplitudes, (b) on slope angles well above‐average (Δ ∼ 10°), and (c) in regions with above‐average rock abundance. We do not observe a qualitatively or statistically relevant relation between rockfall abundance, monitored Apollo‐era shallow seismic activity, and the distribution of visible tectogenetic features. Informed by our global analysis, we conduct a targeted, in‐depth study of 687 rockfall boulders and trajectories in 13 sites across the Moon, including 7 craters, 2 volcanic vents, 2 tectonic structures, and 2 unclassified geomorphic regions. We identify four different source region types, where the type appears to control the occurrence of rockfalls. The source region type in turn is controlled by surface age rather than geomorphic context. We find that rockfall trajectories are mainly controlled by the trigger energy and the geometry of the slope. Our results suggest that erratic small‐scale impacts (mainly in old, Imbrian‐Nectarian, shallow terranes), aided by solar‐induced thermal fatigue of fractured bedrock (mainly in young, Copernican‐Eratosthenian steep terranes), were the dominant, global‐scale long‐ and short‐term drivers of rockfalls in the Moon's recent geologic past.
    Description: Plain Language Summary: The processes that drive rockfall occurrence are largely unknown, but could provide valuable information about the past and current evolution of the Moon's surface and interior. We compare the global distribution of rockfalls with a series of maps, such as seismic, topographic, thermal, and gravity anomaly maps and observe that rockfalls mainly occur (a) on equator‐facing slopes and thus in regions with large temperature differences, (b) on slope angles above‐average, and (c) in regions with rocky surfaces. We do not observe a relation between rockfall abundance, Apollo‐era seismic activity, and the distribution of visible tectonic features. Informed by our global‐scale analysis we study 687 rockfalls in 13 sites of interest in greater detail, including volcanic‐, tectonic‐, and impact‐related geomorphic regions. We observe that the source region type appears to control rockfall occurrence, which in turn is controlled by the surface age. We find that the lunar rockfall transport process appears to be mainly controlled by the driver energy and the steepness of the slope. Our results suggest that small‐scale impacts (mainly in old, shallow regions) and solar‐driven thermal breakdown of fractured bedrock (mainly in young, steep regions) were the main, global‐scale drivers of rockfalls in the Moon's recent geologic past.
    Description: Key Points: We study the drivers and transport mechanisms of lunar rockfalls on a local and global scale. The two dominant, global‐scale rockfall drivers appear to be: (a) impacts and (b) solar‐driven thermal fatigue. The rockfall driver depends on the source region age and type rather than the geomorphic context.
    Description: Max Planck Institute for Solar System Research
    Description: ETH Zurich
    Description: Engineering Geology group, Department of Earth Sciences, International Max Planck Research School
    Description: http://wms.lroc.asu.edu/lroc/search
    Keywords: ddc:523
    Language: English
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    Geological History of Southeastern Gorgonum Chaos, Mars: A Story of Water and Wind (2021)
    Details
    Publication Date: 2022-03-29
    Description: Gorgonum Chaos is part of the Eridania paleolake in Terra Sirenum and displays a number of prominent light‐toned morphological features that bear a record of the regional climatic conditions throughout most of Martian history. Based on an intergrated analysis of orbital data, we mapped a 1,500 km2 area in the southeast of Gorgonum Chaos. Morphologic, spectroscopic, and stratigraphic analyses were used to determine age and composition of the main geological units in the area. We identified four major geological units with decreasing content of hydrated minerals from the oldest to the youngest units, which were completely free of hydrated minerals. In the study area, phyllosilicate‐rich Noachian units compose the majority of the basin floor. Deposits enriched with evaporites were formed around the Noachian/Hesperian transition and erosion created prominent inverted morphologies. Loess‐like material without significant amounts of hydrated minerals was deposited until the late Hesperian. The youngest unit is an Amazonian layer free of hydrated minerals that originated from volcanic activities. This succession of minerals reflects the transition from more humid climatic conditions with the ability to sustain liquid water on the planet's surface during the Noachian to the hyper‐arid Amazonian environment we observe currently on Mars.
    Description: Plain Language Summary: Gorgonum Chaos is part of the Eridania basin, which is a former lake system located at the southern hemisphere of Mars. The landforms observed in this area and their variable brightness suggest dramatically changing climatic conditions during the history of Mars. In an area of 1,500 km2 in size, we analyzed different landforms, their spectral characteristics, and their temporal sequences to determine the age and composition of the geological units. We found four major geologic units whose content of hydrated minerals decreased dramatically from oldest to youngest. The oldest unit with a high content of clay minerals is about 3.7 billion years old and formed the former lake bottom. This is followed by a younger unit with a mineral composition that indicates desiccation of the lake and erosion by wind. These, in turn, were largely covered by materials deposited by wind, which show very little evidence of liquid water. The last and youngest unit is volcanic in origin and completely devoid of minerals indicative of water. This succession of minerals reflects the evolution of the Martian surface, which was capable to sustain liquid water in the early stages of the planet and lost this ability during a drastic climate change.
    Description: Key Points: We produced a geological map of southeastern Gorgonum Chaos. We find a succession from phyllosilicates to olivine in aeolian deposits. The presence of water decreases over time.
    Keywords: ddc:523
    Language: English
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    Reanalysis in Earth System Science: Toward Terrestrial Ecosystem Reanalysis (2021)
    Details
    Publication Date: 2022-03-29
    Description: A reanalysis is a physically consistent set of optimally merged simulated model states and historical observational data, using data assimilation. High computational costs for modeled processes and assimilation algorithms has led to Earth system specific reanalysis products for the atmosphere, the ocean and the land separately. Recent developments include the advanced uncertainty quantification and the generation of biogeochemical reanalysis for land and ocean. Here, we review atmospheric and oceanic reanalyzes, and more in detail biogeochemical ocean and terrestrial reanalyzes. In particular, we identify land surface, hydrologic and carbon cycle reanalyzes which are nowadays produced in targeted projects for very specific purposes. Although a future joint reanalysis of land surface, hydrologic, and carbon processes represents an analysis of important ecosystem variables, biotic ecosystem variables are assimilated only to a very limited extent. Continuous data sets of ecosystem variables are needed to explore biotic‐abiotic interactions and the response of ecosystems to global change. Based on the review of existing achievements, we identify five major steps required to develop terrestrial ecosystem reanalysis to deliver continuous data streams on ecosystem dynamics.
    Description: Plain Language Summary: A reanalysis is a unique set of continuous variables produced by optimally merging a numerical model and observed data. The data are merged with the model using available uncertainty estimates to generate the best possible estimate of the target variables. The framework for generating a reanalysis consists of the model, the data, and the model‐data‐fusion algorithm. The very specific requirements of reanalysis frameworks have led to the development of Earth‐compartment specific reanalysis for the atmosphere, the ocean and land. Here, we review atmospheric and oceanic reanalyzes, and in more detail biogeochemical ocean and terrestrial reanalyzes. In particular, we identify land surface, hydrologic, and carbon cycle reanalyzes which are nowadays produced in targeted projects for very specific purposes. Based on a review of existing achievements, we identify five major steps required to develop reanalysis for terrestrial ecosystem to shed more light on biotic and abiotic interactions. In the future, terrestrial ecosystem reanalysis will deliver continuous data streams on the state and the development of terrestrial ecosystems.
    Description: Key Points: Reanalyzes provide decades‐long model‐data‐driven harmonized and continuous data sets for new scientific discoveries. Novel global scale reanalyzes quantify the biogeochemical ocean cycle, terrestrial carbon cycle, land surface, and hydrologic processes. New observation technology and modeling capabilities allow in the near future production of advanced terrestrial ecosystem reanalysis.
    Description: European Union's Horizon 2020 research and innovation programme
    Description: Deutsche Forschungsgemeinschaft
    Description: U.S. Department of Energy
    Description: Emory University's Halle Institute for Global Research and the Halle Foundation Collaborative Research
    Description: NSF
    Description: NASA
    Description: Natural Environment Research Council
    Description: European Union'’s Horizon 2020 research and innovation programme
    Description: NSERC Discovery program, the Ocean Frontier Institute, and MEOPAR
    Description: Research Foundation Flanders (FWO)
    Description: Helmholtz Association
    Description: NASA Terrestrial Ecosystems
    Keywords: ddc:550
    Language: English
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    An Adaptive Hybrid Vertical Equilibrium/Full‐Dimensional Model for Compositional Multiphase Flow (2022)
    Details
    Publication Date: 2022-06-26
    Description: Efficient compositional models are required to simulate underground gas storage in porous formations where, for example, gas quality (such as purity) and loss of gas due to dissolution are of interest. We first extend the concept of vertical equilibrium (VE) to compositional flow, and derive a compositional VE model by vertical integration. Second, we present a hybrid model that couples the efficient compositional VE model to a compositional full‐dimensional model. Subdomains, where the compositional VE model is valid, are identified during simulation based on a VE criterion that compares the vertical profiles of relative permeability at equilibrium to the ones simulated by the full‐dimensional model. We demonstrate the applicability of the hybrid model by simulating hydrogen storage in a radially symmetric, heterogeneous porous aquifer. The hybrid model shows excellent adaptivity over space and time for different permeability values in the heterogeneous region, and compares well to the full‐dimensional model while being computationally efficient, resulting in a runtime of roughly one‐third of the full‐dimensional model. Based on the results, we assume that for larger simulation scales, the efficiency of this new model will increase even more.
    Description: Key Points: A compositional vertical equilibrium model is coupled to its full‐dimensional counterpart. A criterion is developed to adaptively identify and assign regions where the vertical equilibrium model is applicable during simulation. A test case of hydrogen storage in a heterogeneous porous aquifer demonstrates efficiency and accuracy of the hybrid model.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: https://git.iws.uni-stuttgart.de/dumux-pub/Becker2021b.git
    Keywords: ddc:551.49 ; ddc:550
    Language: English
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    Evolution of Rift Systems and Their Fault Networks in Response to Surface Processes (2022)
    Details
    Publication Date: 2022-06-26
    Description: Continental rifting is responsible for the generation of major sedimentary basins, both during rift inception and during the formation of rifted continental margins. Geophysical and field studies revealed that rifts feature complex networks of normal faults but the factors controlling fault network properties and their evolution are still matter of debate. Here, we employ high‐resolution 2D geodynamic models (ASPECT) including two‐way coupling to a surface processes (SP) code (FastScape) to conduct 12 models of major rift types that are exposed to various degrees of erosion and sedimentation. We further present a novel quantitative fault analysis toolbox (Fatbox), which allows us to isolate fault growth patterns, the number of faults, and their length and displacement throughout rift history. Our analysis reveals that rift fault networks may evolve through five major phases: (a) distributed deformation and coalescence, (b) fault system growth, (c) fault system decline and basinward localization, (d) rift migration, and (e) breakup. These phases can be correlated to distinct rifted margin domains. Models of asymmetric rifting suggest rift migration is facilitated through both ductile and brittle deformation within a weak exhumation channel that rotates subhorizontally and remains active at low angles. In sedimentation‐starved settings, this channel satisfies the conditions for serpentinization. We find that SP are not only able to enhance strain localization and to increase fault longevity but that they also reduce the total length of the fault system, prolong rift phases and delay continental breakup.
    Description: Plain Language Summary: Continental rifting is responsible for breaking apart continents and forming new oceans. Rifts generally evolve according to three types: wide rift, symmetric rift, and asymmetric rifts, which also shape the final geometry of the continental rifted margin. Geophysical data shows that the evolution of rifts depends on a multitude of factors including the complex interactions between fault networks that accommodate extension and the processes of erosion and sediment deposition. Here we run 2D computer simulations to investigate fault network evolution during active rifting that include changes to the surface through erosion and sedimentation. By using a new python tool box, we extract the fault network from the simulation and determine individual fault properties like the number of faults, displacement, age, and length through time. We find that regardless of the rift type, rifts evolve according to five phases that can be assessed through the evolution of the fault network properties. Additionally, we find that greater erosion and sedimentation can prolong rift phases and delay the breakup of continents.
    Description: Key Points: We apply a new fault analysis toolbox to coupled numerical models of tectonics and surface processes. Fault network evolution of the major symmetric, asymmetric, narrow, and wide rift types can be described in five distinct phases. Surface processes reduce fault network complexity and delay breakup by enhancing strain localization and increasing fault longevity.
    Description: Helmholtz Young Investigators
    Description: National Science Foundation
    Description: Deutsche Forschungsgemeinschaft (DFG)
    Description: https://doi.org/10.5281/zenodo.5753144
    Keywords: ddc:551.8
    Language: English
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    The Vertical Structure and Entrainment of Subglacial Melt Water Plumes (2022)
    Details
    Publication Date: 2022-06-22
    Description: Basal melting of marine‐terminating glaciers, through its impact on the forces that control the flow of the glaciers, is one of the major factors determining sea level rise in a world of global warming. Detailed quantitative understanding of dynamic and thermodynamic processes in melt‐water plumes underneath the ice‐ocean interface is essential for calculating the subglacial melt rate. The aim of this study is therefore to develop a numerical model of high spatial and process resolution to consistently reproduce the transports of heat and salt from the ambient water across the plume into the glacial ice. Based on boundary layer relations for momentum and tracers, stationary analytical solutions for the vertical structure of subglacial non‐rotational plumes are derived, including entrainment at the plume base. These solutions are used to develop and test convergent numerical formulations for the momentum and tracer fluxes across the ice‐ocean interface. After implementation of these formulations into a water‐column model coupled to a second‐moment turbulence closure model, simulations of a transient rotational subglacial plume are performed. The simulated entrainment rate of ambient water entering the plume at its base is compared to existing entrainment parameterizations based on bulk properties of the plume. A sensitivity study with variations of interfacial slope, interfacial roughness and ambient water temperature reveals substantial performance differences between these bulk formulations. An existing entrainment parameterization based on the Froude number and the Ekman number proves to have the highest predictive skill. Recalibration to subglacial plumes using a variable drag coefficient further improves its performance.
    Description: Plain Language Summary: In a world of global warming, the melting of glaciers terminating as floating ice tongues into the oceans of Arctic and Antarctic regions allows those glaciers to flow faster and hence to make a considerable contribution to global mean sea‐level rise. Underneath the ice‐ocean interface, turbulent currents of the order of 10 m thickness (so‐called plumes) develop that transport the melt water from the grounding line where the glacier enters the ocean toward the calving front that marks the seaward end of the glacier. At its base, ambient relatively warm and salty ocean water is mixed into the plumes and is vertically transported toward the ice‐ocean interface, where the melting is increased due to the additional heat supply. Understanding these processes is essential for their incorporation into computer models for the prediction of such melt processes. In this study, an accurate simulation model for the water column is constructed that is able to consistently reproduce these processes. The algorithms developed here are proven to provide reliable results also for models with only a few grid points across the plume and can therefore be implemented into climate models with surface‐following coordinates to more accurately simulate future scenarios of sea level rise.
    Description: Key Points: A vertically resolving model with second‐moment turbulence closure has been constructed for subglacial plumes. Convergent numerical formulations for the ocean‐to‐ice fluxes of momentum, freshwater and heat have been derived from an analytical model. Model results are consistent with bulk parameterizations for the entrainment of ambient water.
    Description: Bundesministerium für Bildung und Forschung (BMBF) http://dx.doi.org/10.13039/501100002347
    Description: https://doi.org/10.5281/zenodo.6203838
    Keywords: ddc:550
    Language: English
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    Modeling Subsurface Hydrogen Storage With Transport Properties From Entropy Scaling Using the PC‐SAFT Equation of State (2022)
    Details
    Publication Date: 2022-10-17
    Description: Hydrogen is a promising alternative to carbon based energy carriers and may be stored in large quantities in subsurface storage deposits. This work assesses the impact of static (density and phase equilibria) and dynamic (viscosity and diffusion coefficients) properties on the pressure field during the injection and extraction of hydrogen in the porous subsurface. In a first step, we derive transport properties for water, hydrogen and their mixture using the Perturbed‐Chain Statistical Associating Fluid Theory equation of state in combination with an entropy scaling approach and compare model predictions to alternative models from the literature. Our model compares excellently to experimental transport coefficients and models from literature with a higher number of adjustable parameters, such as GERG2008, and shows a clear improvement over empirical correlations for transport coefficients of hydrogen. In a second step, we determine the effect of further model reduction by comparing our against a much simpler model applying empirical transport coefficients from the literature. For this purpose, hydrogen is periodically injected into and extracted out of a dome‐shaped porous aquifer under a caprock. Our results show that density and viscosity of hydrogen have the highest impact on the pressure field, and that a thermodynamic model like the new model presented here is essential for modeling the storage aquifer, while keeping the number of coefficients at a minimum. In diffusion‐dominated settings such as the diffusion of hydrogen through the caprock, our developed diffusion coefficients show a much improved dependence on temperature and pressure, leading to a more accurate approximation of the diffusive fluxes.
    Description: Key Points: We model the phase behavior of pure hydrogen and the binary hydrogen‐water mixture using the Perturbed‐Chain Statistical Associating Fluid Theory equation of state. New entropy scaling relations for the transport properties of hydrogen and water and diffusion coefficients of their mixture are derived. The impact of the newly derived fluid properties is analyzed for a scenario of hydrogen storage in a porous aquifer.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: https://git.iws.uni-stuttgart.de/dumux-pub/sauerborn2020a
    Keywords: ddc:550
    Language: English
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    An Energy Conserving Vlasov Solver That Tolerates Coarse Velocity Space Resolutions: Simulation of MMS Reconnection Events (2022)
    Details
    Publication Date: 2022-08-05
    Description: Vlasov solvers that operate on a phase‐space grid are highly accurate but also numerically demanding. Coarse velocity space resolutions, which are largely unproblematic in particle‐in‐cell (PIC) simulations, can lead to numerical heating or oscillations in continuum Vlasov methods. To address this issue, we present a new dual Vlasov solver which is based on an established positivity preserving advection scheme for the update of the distribution function and an energy conserving partial differential equation solver for the kinetic update of mean velocity and temperature. The solvers work together via moment fitting during which the maximum entropy part of the distribution function is replaced by the solution from the partial differential equation solver. This numerical scheme makes continuum Vlasov methods competitive with PIC methods concerning computational cost and enables us to model large scale reconnection in Earth's magnetosphere with a fully kinetic continuum method. The simulation results agree well with measurements by the MMS spacecraft.
    Description: Key Points: A moment fitting continuum Vlasov solver is presented that preserves positivity of the distribution function and conserves total energy. The method behaves well at low velocity space resolutions, making it competitive with PIC methods concerning computational cost. There is good agreement of the simulations with measurements of magnetic reconnection by the MMS spacecraft.
    Description: Helmholtz Association (亥姆霍兹联合会致力) http://dx.doi.org/10.13039/501100009318
    Description: https://vlasov.tp1.ruhr-uni-bochum.de/data/paper-JGR-2021
    Keywords: ddc:550 ; ddc:538.7
    Language: English
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    Asteroid 2008 TC3, not a polymict ureilitic but a polymict C1 chondrite parent body? Survey of 249 Almahata Sitta fragments (2022)
    Details
    Publication Date: 2022-09-30
    Description: On October 7, 2008, the asteroid 2008 TC3 exploded as it entered the Earth’s atmosphere, producing significant dust (in the atmosphere) and delivering thousands of stones in a strewn field in Sudan, collectively known as the Almahata Sitta (AhS) stones. About 600 fragments were officially recovered in 2008 and 2009. Further rocks were collected since the fall event by local people. From these stones, 249 were classified at the Institut für Planetologie in Münster (MS) known as MS‐xxx or MS‐MU‐xxx AhS subsamples. Most of these rocks are ureilitic in origin (168; 67%): 87 coarse‐grained ureilites, 60 fine‐grained ureilites, 15 ureilites with variable texture/mineralogy, four trachyandesites, and two polymict breccias. We identified 81 non‐ureilitic fragments, corresponding to 33% of the recovered samples studied in Münster. These included chondrites, namely 65 enstatite chondrites (43 EL; 22 EH), 11 ordinary chondrites (OC), one carbonaceous chondrite, and one unique R‐like chondrite. Furthermore, three samples represent a unique type of enstatite achondrite. Since all AhS stones must be regarded as individual specimens independent from each other, the number of fresh ureilite and enstatite chondrite falls in our meteorite collections has been increased by several hundred percent. Overall, the samples weigh between 〈1 and 250 g and have a mean mass of ~15 g. If we consider—almost 15 years after the fall—the mass calculations, observations during and after the asteroid entered the atmosphere, the mineralogy of the C1 stones AhS 91A and AhS 671, and the experimental work on fitting the asteroid spectrum (e.g., Goodrich et al., 2019; Jenniskens et al., 2010; Shaddad et al., 2010), the main portion of the meteoroid was likely made of the fine‐grained (carbonaceous) dust and was mostly lost in the atmosphere. In particular, the fact that C1 materials were found has important implications for interpreting asteroid 2008 TC3's early spectroscopic results. Goodrich et al. (2019) correctly suggested that if scientists had not recovered the “water‐free” samples (e.g., ureilites, enstatites, and OC) from the AhS strewn field, 2008 TC3 would have been assumed to be a carbonaceous chondrite meteoroid. Considering that the dominating mass of the exploding meteoroid consisted of carbonaceous materials, asteroid 2008 TC3 cannot be classified as a polymict ureilite; consequently, we state that the asteroid was a polymict carbonaceous chondrite breccia, specifically a polymict C1 object that may have formed by late accretion at least 50–100 Ma after calcium–aluminum‐rich inclusions.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Alexander von Humboldt Foundation http://dx.doi.org/10.13039/100005156
    Keywords: ddc:549.112 ; ddc:523
    Language: English
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    Spatio‐Temporal Level Variations of the Martian Seasonal South Polar Cap From Co‐Registration of MOLA Profiles (2022)
    Details
    Publication Date: 2022-10-04
    Description: The seasonal deposition and sublimation of CO2 represents a major element in the Martian volatile cycle. Here, co‐registration strategies are applied to Mars Orbiter Laser Altimeter profiles to obtain spatio‐temporal variations in snow/ice level of the Seasonal South Polar Cap (SSPC), in grid elements of 0.5° in latitude from 60° to 87°S and 10° in longitude. The maximum snow/ice level in the range of 2–2.5 m is observed over the Residual South Polar Cap. Peak level at the Residual South Polar Cap in Martian Year 25 (MY25) are found to be typically ∼0.5 m higher than those in MY24. The total volume is estimated to peak at approximately 9.4 × 1012 m3. In addition, a map of average bulk density of the SSPC during its recession is derived. It implies much more snowfall‐like precipitation at the Residual South Polar Cap and its surroundings than elsewhere on Mars.
    Description: Plain Language Summary: Each Martian year, up to one third of the atmosphere's CO2 is transported from pole to pole, being deposited and sublimated depending on the season. Accurate measurements of snow level and volume variations of the resulting seasonal polar caps can serve as crucial constraints on the Martian volatile cycles. In this study, we apply new approaches of analyzing the Mars Orbiter Laser Altimeter profiles, which lead to spatially and temporally resolved measurements of snow/ice level of the Seasonal South Polar Cap (SSPC). Based on that, the maximum snow level, interannual maximum level change from Martian Year 24 (MY24) to MY25, and how the volume of the SSPC changes with time are measured. We also estimate the bulk density of the snow/ice deposition during southern winter. It is inferred that there is much more snowfall at the Residual South Polar Cap and its surroundings than elsewhere on the planet.
    Description: Key Points: Using co‐registration of Mars Orbiter Laser Altimeter profiles, spatio‐temporal level variations of the seasonal snow/ice deposits at the Martian south pole are obtained. Maximum level can be up to 2.5 m; Peak level increased by ∼0.5 m at the Residual South Polar Cap from Martian Year 24 (MY24) to MY25. Obtained bulk density map of the seasonal deposits implies that snowfall concentrates at the Residual South Polar Cap and its surroundings.
    Description: China Scholarship Council
    Description: Deutsche Forschungsgemeinschaft
    Description: Institut National des Sciences de l’Univers
    Description: Centre National de la Recherche Scientifique
    Description: Centre National d’Etudes Spatiales
    Description: https://pds-geosciences.wustl.edu/missions/mgs/pedr.html
    Description: https://naif.jpl.nasa.gov/pub/naif/pds/data/mgs-m-spice-6-v1.0/mgsp_1000/data/
    Description: https://doi.org/10.17632/z59b9nd6s9.2
    Description: https://doi.org/10.14768/8cba4407-d6a0-4d16-aeaf-d0ebfd2b480a
    Keywords: ddc:523
    Language: English
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    Spatial Markov Model for the Prediction of Travel‐Time‐Based Solute Dispersion in Three‐Dimensional Heterogeneous Media (2022)
    Details
    Publication Date: 2022-10-05
    Description: In recent years, Spatial Markov Models have gained popularity in simulating solute transport in heterogeneous formations. They describe the transition times of particles between equidistant observation planes by statistical distributions, assuming correlation of the transit times of individual particles between subsequent steps. By this, the approach naturally captures preasymptotic solute dispersion. In this study, we analyze Spatial Markov Models assuming bivariate log‐normal distributions of the particle slowness (i.e., the inverse velocity) in subsequent transitions. The model is fully parameterized by the mean Eulerian velocity, the variance of the log‐slowness, and the correlation coefficient of log‐slowness in subsequent steps. We derive closed‐form expressions for distance‐dependent ensemble dispersion, which is defined in terms of the second‐central moments of the solute breakthrough curves. We relate the coefficients to the properties of the underlying log‐hydraulic conductivity field assuming second‐order stationarity. The results are consistent with linear stochastic theory in the limit of small log‐conductivity variances, while the approach naturally extends to high‐variance cases. We demonstrate the validity of the approach by comparison to three‐dimensional particle‐tracking simulations of advective transport in heterogeneous media with isotropic, exponential correlation structure for log‐conductivity variances up to five. This study contributes to relating solute dispersion to metrics of the porous‐medium structure in cases of strong heterogeneity.
    Description: Key Points: We derive closed‐form expressions of ensemble dispersion in the spatial‐Markov framework of solute transport. The expressions are consistent with linear theory in the limit of small log‐conductivity variances, but extend to high‐variance cases. Comparison to particle‐tracking simulations of advective transport in 3‐D heterogeneous domains show excellent agreement.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: https://doi.org/10.5281/zenodo.6554308
    Description: https://www.hsl.rl.ac.uk/catalogue/hsl_mi20.html
    Keywords: ddc:550
    Language: English
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    Mapping the Brightness of Ganymede's Ultraviolet Aurora Using Hubble Space Telescope Observations (2022)
    Details
    Publication Date: 2022-10-06
    Description: We analyze Hubble Space Telescope observations of Ganymede made with the Space Telescope Imaging Spectrograph between 1998 and 2017 to generate a brightness map of Ganymede's oxygen emission at 1,356 Å. Our Mercator projected map demonstrates that the brightness along Ganymede's northern and southern auroral ovals strongly varies with longitude. To quantify this variation around Ganymede, we investigate the brightness averaged over 36°‐wide longitude corridors centered around the sub‐Jovian (0° W), leading (90° W), anti‐Jovian (180° W), and trailing (270° W) central longitudes. In the northern hemisphere, the brightness of the auroral oval is 3.7 ± 0.4 times lower in the sub‐Jovian and anti‐Jovian corridors compared to the trailing and leading corridors. The southern oval is overall brighter than the northern oval, and only 2.5 ± 0.2 times fainter on the sub‐ and anti‐Jovian corridors compared to the trailing and leading corridors. This demonstrates that Ganymede's auroral ovals are strongly structured in auroral crescents on the leading side (plasma downstream side) and on the trailing side (plasma upstream side). We also find that the brightness is not symmetric with respect to the 270° meridian, but shifted by ∼20° towards the Jovian‐facing hemisphere. Our map will be useful for subsequent studies to understand the processes that generate the aurora in Ganymede's non‐rotationally driven, sub‐Alfvénic magnetosphere.
    Description: Plain Language Summary: Northern lights often illuminate the night sky in a shimmering green or red tone at high geographic latitudes. This emission, scientifically referred to as aurora, is a result of electrically charged particles that move along Earth's magnetic field lines and interact with its atmosphere to produce auroral emission. Apart from the Earth, multiple other planets in our solar system also exhibit auroral emission. By characterizing the brightness and structure of these lights, we are therefore able to deduce insights about a planet's atmosphere, magnetic field and the physical processes occurring along the field lines from afar. In this work, we used observations from the Hubble Space Telescope to analyze the auroral emission of Jupiter's largest moon Ganymede. We combined multiple images of Ganymede to create the first complete map that displays the auroral brightness. Our map revealed that the emission on Ganymede's auroral ovals varies strongly in brightness with divisions into two distinct bright and faint regions. They resemble two auroral crescents in the north and south respectively, and demonstrate the uniqueness of Ganymede's aurora in comparison with the auroral ovals of other planets in the solar system.
    Description: Key Points: Brightness map of Ganymede's ultraviolet auroral emission has been constructed based on Hubble Space Telescope observations from 1998 to 2017. Auroral ovals are structured in upstream and downstream “crescents”. Brightness on sub‐Jovian and anti‐Jovian side is strongly reduced by a factor of 3–4 compared to upstream and downstream side.
    Description: European Research Council (ERC)
    Description: http://archive.stsci.edu/hst/
    Keywords: ddc:523
    Language: English
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    Strain Signals Governed by Frictional‐Elastoplastic Interaction of the Upper Plate and Shallow Subduction Megathrust Interface Over Seismic Cycles (2022)
    Details
    Publication Date: 2022-10-06
    Description: The behavior of the shallow portion of the subduction zone, which generates the largest earthquakes and devastating tsunamis, is still insufficiently constrained. Monitoring only a fraction of a single megathrust earthquake cycle and the offshore location of the source of these earthquakes are the foremost reasons for the insufficient understanding. The frictional‐elastoplastic interaction between the megathrust interface and its overlying wedge causes variable surface strain signals such that the wedge strain patterns may reveal the mechanical state of the interface. To contribute to this understanding, we employ Seismotectonic Scale Modeling and simplify elastoplastic megathrust subduction to generate hundreds of analog seismic cycles at a laboratory scale and monitor the surface strain signals over the model's forearc across high to low temporal resolutions. We establish two compressional and critical wedge configurations to explore the mechanical and kinematic interaction between the shallow wedge and the interface. Our results demonstrate that this interaction can partition the wedge into different segments such that the anelastic extensional segment overlays the seismogenic zone at depth. Moreover, the different segments of the wedge may switch their state from compression/extension to extension/compression domains. We highlight that a more segmented upper plate represents megathrust subduction that generates more characteristic and periodic events. Additionally, the strain time series reveals that the strain state may remain quasi‐stable over a few seismic cycles in the coastal zone and then switch to the opposite mode. These observations are crucial for evaluating earthquake‐related morphotectonic markers and short‐term interseismic time series of the coastal regions.
    Description: Key Points: Analog earthquake cycle experiments provide observations to evaluate the surface strain signals from the shallow megathrust. The extensional segment of the forearc overlays the seismogenic zone at depth. The strain state may remain quasi‐stable over a few seismic cycles in the coastal zone.
    Description: SUBITOP Marie Sklodowska‐Curie Action project from the European Union's EU Framework Programme
    Description: Deutsche Forschungsgemeinschaft (CRC 1114) “Scaling Cascades in Complex Systems”
    Description: https://doi.org/10.5880/fidgeo.2022.015
    Keywords: ddc:551.8 ; ddc:550.78
    Language: English
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    Widening of Hydrous Shear Zones During Incipient Eclogitization of Metastable Dry and Rigid Lower Crust—Holsnøy, Western Norway (2021)
    Details
    Publication Date: 2022-08-26
    Description: The partially eclogitized crustal rocks on Holsnøy in the Bergen Arcs, Norway, indicate that eclogitization is caused by the interplay of brittle and ductile deformation promoted by fluid infiltration and fluid‐rock interaction. Eclogitization generated an interconnected network of millimeter‐to‐kilometer‐wide hydrous eclogite‐facies shear zones, which presumably caused transient weakening of the mechanically strong lower crust. To decipher the development of those networks, we combine detailed lithological and structural mapping of two key outcrops with numerical modeling. Both outcrops are largely composed of preserved granulite with minor eclogite‐facies shear zones, thus representing the beginning phases of eclogitization and ductile deformation. We suggest that deformation promoted fluid‐rock interaction and eclogitization, which gradually consumed the granulite until fluid‐induced reactions were no longer significant. The shear zones widen during progressive deformation. To identify the key parameters that impact shear zone widening, we generated scale‐independent numerical models, which focus on different processes affecting the shear zone evolution: (i) rotation of the shear zones caused by finite deformation, (ii) mechanical weakening due to a limited amount of available fluid, and (iii) weakening and further hydration of the shear zones as a result of continuous and unlimited fluid supply. A continuous diffusion‐type fluid infiltration, with an effective diffusion coefficient around D=10−16m2s, coupled with deformation is prone to develop structures similar to the ones mapped in field. Our results suggest that the shear zones formed under a continuous fluid supply, causing shear zone widening, rather than localization, during progressive deformation.
    Description: Key Points: Continuous fluid supply causes shear zone widening. Shear zones widen during strain accumulation.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: Norges Forskningsråd http://dx.doi.org/10.13039/501100005416
    Keywords: ddc:551.8
    Language: English
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    Historical Earthquakes, Paleoseismology, Neotectonics and Seismic Hazard: New Insights and Suggested Procedures (2020)
    Deutsche Gesellschaft für Erdbebeningenieurwesen und Baudynamik (DGEB) e.V. | Kiel
    Details
    Publication Date: 2022-07-13
    Description: This publication developed from the 5th International Colloquium on “Historical Earthquakes, Paleoseismology, Neotectonics and Seismic Hazard” which was held from 11 to 13 October 2017 at the Federal Institute for Geosciences and Natural Resources (BGR) in Hannover, Germany. In this colloquium, 75 experts from 17 countries presented and discussed recent results, ongoing studies and planned projects on the topics historical earthquakes, macroseismology, archeoseismology, paleoseismology, earthquake catalogues and databases, active faults, seismotectonics, neotectonics, and seismic hazard assessment.
    Description: Deutsche Gesellschaft für Erdbebeningenieurwesen und Baudynamik
    Description: 〈b〉Introduction: Historical Earthquakes, Paleoseismology, Neotectonics and Seismic Hazard: New Insights and Suggested Procedures〈/b〉 〈br〉 〈i〉Diethelm Kaiser〈/i〉 〈br〉 〈a href="https://doi.org/10.23689/fidgeo-3868"〉 DOI: https://doi.org/10.23689/fidgeo-3868〈/a〉〈br〉 〈br〉〈/br〉 〈b〉Best practice of macroseismic intensity assessment applied to the earthquake catalogue of southwestern Germany〈/b〉 〈br〉 〈i〉 Wolfgang Brüstle, Uwe Braumann, Silke Hock and Fee-Alexandra Rodler 〈/i〉〈br〉 〈a href="https://doi.org/10.23689/fidgeo-3864"〉 DOI:https://doi.org/10.23689/fidgeo-3864〈/a〉〈br〉 〈br〉〈/br〉 〈b〉The earthquake of September 3, 1770 near Alfhausen (Lower Saxony, Germany): a real, doubtful, or a fake event? 〈/b〉 〈br〉 〈i〉Günter Leydecker and Klaus Lehmann 〈/i〉 〈br〉〈a href="https://doi.org/10.23689/fidgeo-3865"〉 DOI: https://doi.org/10.23689/fidgeo-3865〈/a〉〈br〉 〈br〉〈/br〉 〈b〉How well does known seismicity between the Lower Rhine Graben and southern North Sea reflect future earthquake activity? 〈/b〉 〈br〉 〈i〉Thierry Camelbeeck, Kris Vanneste, Koen Verbeeck, David Garcia-Moreno, Koen Van Noten and Thomas Lecocq 〈/i〉 〈br〉〈a href="https://doi.org/10.23689/fidgeo-3866"〉 DOI: https://doi.org/10.23689/fidgeo-3866〈/a〉〈br〉 〈br〉〈/br〉 〈b〉The Paleoseismic Database of Germany and Adjacent Regions PalSeisDB v1.0〈/b〉〈br〉 〈i〉Jochen Hürtgen, Klaus Reicherter, Thomas Spies, Claudia Geisler and Jörg Schlittenhardt 〈/i〉 〈br〉〈a href="https://doi.org/10.23689/fidgeo-3867"〉 DOI: https://doi.org/10.23689/fidgeo-3867〈/a〉〈br〉
    Description: research
    Keywords: ddc:551.22 ; ddc:554.3 ; ddc:550
    Language: English
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    Controls of the Foreland Deformation Pattern in the Orogen‐Foreland Shortening System: Constraints From High‐Resolution Geodynamic Models (2022)
    Details
    Publication Date: 2022-09-22
    Description: Controls on the deformation pattern (shortening mode and tectonic style) of orogenic forelands during lithospheric shortening remain poorly understood. Here, we use high‐resolution 2D thermomechanical models to demonstrate that orogenic crustal thickness and foreland lithospheric thickness significantly control the shortening mode in the foreland. Pure‐shear shortening occurs when the orogenic crust is not thicker than the foreland crust or thick, but the foreland lithosphere is thin (〈70–80 km, as in the Puna foreland case). Conversely, simple‐shear shortening, characterized by foreland underthrusting beneath the orogen, arises when the orogenic crust is much thicker. This thickened crust results in high gravitational potential energy in the orogen, which triggers the migration of deformation to the foreland under further shortening. Our models present fully thick‐skinned, fully thin‐skinned, and intermediate tectonic styles in the foreland. The first tectonics forms in a pure‐shear shortening mode whereas the others require a simple‐shear mode and the presence of thick (〉∼4 km) sediments that are mechanically weak (friction coefficient 〈∼0.05) or weakened rapidly during deformation. The formation of fully thin‐skinned tectonics in thick and weak foreland sediments, as in the Subandean Ranges, requires the strength of the orogenic upper lithosphere to be less than one‐third as strong as that of the foreland upper lithosphere. Our models successfully reproduce foreland deformation patterns in the Central and Southern Andes and the Laramide province.
    Description: Key Points: Thicknesses of the orogenic crust and the foreland lithosphere control the foreland shortening mode (pure‐shear or simple‐shear). Foreland weak sediments and the upper lithosphere of the weaker orogen control the foreland tectonic style (thin‐skinned or thick‐skinned). High‐resolution geodynamic models successfully reproduce foreland deformation patterns in several natural orogen‐foreland shortening systems.
    Description: Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659
    Description: https://bitbucket.org/bkaus/LaMEM
    Description: https://doi.org/10.5281/zenodo.5963016
    Keywords: ddc:551.8
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    Alternating Emission Features in Io's Footprint Tail: Magnetohydrodynamical Simulations of Possible Causes (2022)
    Details
    Publication Date: 2022-09-22
    Description: Io's movement relative to the plasma in Jupiter's magnetosphere creates Alfvén waves propagating along the magnetic field lines which are partially reflected along their path. These waves are the root cause for auroral emission, which is subdivided into the Io Footprint (IFP), its tail and leading spot. New observations of the Juno spacecraft by Mura et al. (2018, https://doi.org/10.1126/science.aat1450) have shown puzzling substructure of the footprint and its tail. In these observations, the symmetry between the poleward and equatorward part of the footprint tail is broken and the tail spots are alternatingly displaced. We show that the location of these bright spots in the tail are consistent with Alfvén waves reflected at the boundary of the Io torus and Jupiter's ionosphere. Then, we investigate three different mechanisms to explain this phenomenon: (a) The Hall effect in Io's ionosphere, (b) travel time differences of Alfvén waves between Io's Jupiter facing and its opposing side and (c) asymmetries in Io's atmosphere. For that, we use magnetohydrodynamic simulations within an idealized geometry of the system. We use the Poynting flux near the Jovian ionosphere as a proxy for the morphology of the generated footprint and its tail. We find that the Hall effect is the most important mechanism under consideration to break the symmetry causing the “Alternating Alfvén spot street.” The travel time differences contributes to enhance this effect. We find no evidence that the inhomogeneities in Io's atmosphere contribute significantly to the location or shape of the tail spots.
    Description: Key Points: Hall effect in Io's ionosphere produces Poynting flux morphology similar to observed alternating Alfvén spot street in Io footprint tail (IFP). Alfvén wave travel time difference and asymmetries in Io's atmosphere are not sufficient to produce observed structures in IFP. IFP emission inter‐spot distance correlates with reflected Alfvén waves.
    Description: Regional Computing Center of the University of Cologne (RRZK)
    Description: European Research Council (ERC)
    Description: http://plutocode.ph.unito.it/download.html
    Keywords: ddc:523
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    From the Top of Martian Olympus to Deep Craters and Beneath: Mars Radiation Environment Under Different Atmospheric and Regolith Depths (2022)
    Details
    Publication Date: 2022-06-17
    Description: In preparation for future human habitats on Mars, it is important to understand the Martian radiation environment. Mars does not have an intrinsic magnetic field and Galactic cosmic ray (GCR) particles may directly propagate through and interact with its atmosphere before reaching the surface and subsurface of Mars. However, Mars has many high mountains and low‐altitude craters where the atmospheric thickness can be more than 10 times different from one another. We thus consider the influence of the atmospheric depths on the Martian radiation levels including the absorbed dose, dose equivalent and body effective dose rates induced by GCRs at varying heights above and below the Martian surface. The state‐of‐the‐art Atmospheric Radiation Interaction Simulator based on GEometry And Tracking Monte Carlo method has been employed for simulating particle interactions with the Martian atmosphere and terrain. We find that higher surface pressures can effectively reduce the heavy ion contribution to the radiation, especially the biologically weighted radiation quantity. However, enhanced shielding (both by the atmosphere and the subsurface material) can considerably enhance the production of secondary neutrons which contribute significantly to the effective dose. In fact, both neutron flux and effective dose peak at around 30 cm below the surface. This is a critical concern when using the Martian surface material to mitigate radiation risks. Based on the calculated effective dose, we finally estimate some optimized shielding depths, under different surface pressures (corresponding to different altitudes) and various heliospheric modulation conditions. This may serve for designing future Martian habitats.
    Description: Plain Language Summary: Thanks to Earth's magnetic field and atmosphere, high‐energy cosmic particles can be efficiently shielded from causing radiation risks for humans on Earth. However, for crewed space missions, in particular long‐term missions to Mars, space radiation is a major risk for the health of astronauts. Mars does not have an intrinsic global magnetic field and its atmosphere is too thin to effectively shield against radiation. Here, we model the Martian radiation environment induced by omnipresent cosmic rays in Mars's atmosphere and terrain. Given that Mars has many high mountains and low‐altitude craters where the atmospheric thickness can be more than 10 times different from one another, we also consider different model setups with different atmospheric profiles. We find that with more shielding the heavy ion contribution to the radiation is reduced while the neutron contribution is enhanced. For a given threshold of the annual biologically weighted radiation effective dose, for example, 100 mSv, the required regolith depth ranges between about 1 and 1.6 m. At a deep crater where the surface pressure is higher, the needed extra regolith shielding is slightly smaller. Our study may serve for mitigating radiation risks when designing future Martian habitats using natural surface material as shielding protection.
    Description: Key Points: We calculate dose, dose equivalent, and effective dose rates induced by various components of galactic cosmic rays on and below Mars surface. Surface pressure which is related to geographic altitude influences the surface and subsurface radiation level. Subsurface secondary neutrons contribute significantly to the effective dose and are a critical concern for radiation risks on Mars.
    Description: CAS strategic priority program
    Description: National Natural Science Foundation of China (NSFC) http://dx.doi.org/10.13039/501100001809
    Description: CNSA pre‐research Project on Civil Aerospace Technologies
    Description: The Key Research Program of the Chinese Academy of Sciences
    Description: German Aerospace Center (DLR)
    Description: https://et-wiki.physik.uni-kiel.de/atris/atris
    Keywords: ddc:523
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    Ionospheric Corrections for Satellite Altimetry ‐ Impact on Global Mean Sea Level Trends (2022)
    Details
    Publication Date: 2022-06-16
    Description: Atmospheric delay corrections for satellite altimetry measurements are essential for deriving highly accurate sea surface heights and reliable global mean sea level (GMSL) trend estimates. A commonly used method to correct for ionospheric path delays are the usage of GNSS‐based Global Ionospheric Maps (GIM). The different orbit heights of GNSS and altimeter satellites require an adaption of GIM corrections to account for free electrons in the Earth plasmasphere. This study shows that the widely used scaling approach based on the International Reference Ionosphere (IRI) is not able to accurately scale the GIM models. The impact of neglecting the plasmaspheric part of the atmosphere strongly correlates with the solar activity of about 11 years. This manifests itself as trend errors in global GMSL. For the Jason period (2002–2021) a trend error of 0.17 mm/year can be shown, which is even larger for smaller periods (e.g., 1.0 mm/year for Jason‐1 lifetime). The application of an additional constant scaling factor of 0.886 can reduce the trend differences to below 0.05 mm/year.
    Description: Plain Language Summary: Global mean sea level (GMSL) rise is an important indicator for climate change. To precisely measure this quantity that is only in the order of about 3 mm/year, satellite altimeters are used. Their observations have to be corrected for influences in the Earth atmosphere. This study shows deficiencies in one commonly used correction data set. These corrections, based on observations from the Global Navigation Satellite Systems (GNSS) are not accounting for the higher part of the atmosphere, the plasmasphere. Neglecting this influence derives systematic errors with a 11 years cycle that impacts the estimation of GMSL by up to 1 mm/year, depending on the period under investigation. It is recommended to apply an additional scaling of the available corrections in order to reduce the trend error to below 0.05 mm/year.
    Description: Key Points: Global Ionospheric Map corrections in altimetry Sensor Geophysical Data Records are not fully scaled to account for plasmaspheric electron content. Neglecting the plasmaspheric effect leads to trends of up to 1 mm/year in Global mean sea level estimates. The additional application of a scale factor improves the consistency in trend with respect to dual‐frequency satellite altimetry data.
    Description: https://podaac.jpl.nasa.gov/
    Description: https://www.aviso.altimetry.fr/
    Description: https://openadb.dgfi.tum.de/en/products/vertical-total-electron-content/
    Keywords: ddc:538.767 ; ddc:550
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    Constraining Andean Propagation of Exhumation at the Limit of the Eastern Cordillera, NW Argentina, Using Low‐Temperature Thermochronology in a Structural Context (2022)
    Details
    Publication Date: 2022-12-07
    Description: Within the Central Andes of NW Argentina, the spatiotemporal distribution and style of deformation is strongly influenced by pre‐Cenozoic heterogeneities, mostly related to the Salta rift extension in the Cretaceous. At the enigmatic junction of the thin‐skinned Subandean belt and the thick‐skinned Santa Barbara System, the Tilcara Range and adjacent San Lucas block, located within the Eastern Cordillera, show thermochronological and field evidence of multiple exhumation events. Mesozoic (140‐115 Ma), pre‐Andean exhumation of basement highs is constrained by unconformities between basement and syn‐rift strata, as well as zircon (U‐Th‐Sm)/He cooling ages. Cenozoic Andean exhumation is quantified by apatite (U‐Th‐Sm)/He and fission track cooling ages, which were reset between the Late Cretaceous and Miocene. These data show that the westernmost Tilcara Range began exhuming in the late Oligocene‐early Miocene (26‐16 Ma), after which exhumation propagated to the border of the Eastern Cordillera in the middle Miocene (22‐10 Ma). The onset of rapid exhumation in the San Lucas block, which is located east of the Tilcara Range, occurred in the late Miocene (10‐8 Ma) in its western part, and in the late Miocene‐early Pliocene (6‐4 Ma) in its eastern part. Internal deformation of the San Lucas block, disturbing zircon (U‐Th‐Sm)/He and apatite fission track age patterns, predates propagation of rapid exhumation. The here presented low‐temperature thermochronology data set thus quantifies the multi‐phase exhumation history of the Eastern Cordillera of NW Argentina and constrains the timing of Andean propagation of exhumation within the Eastern Cordillera and the adjacent structural transition zone.
    Description: Key Points: Zircon (U‐Th‐Sm)/He data suggests that pre‐Andean exhumation of Salta rift basement highs occurred in the Early Cretaceous (140‐115 Ma). Apatite (U‐Th‐Sm)/He and fission track data indicate a late Oligocene‐early Miocene (26‐16 Ma) onset of exhumation in the Tilcara Range. Andean exhumation overall propagated in‐sequence eastward, but thermal models indicate the possibility of local out‐of‐sequence movement.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: https://doi.org/10.5281/zenodo.6358993
    Keywords: ddc:551.8 ; low‐temperature thermochronology ; thermal modeling ; structural geology ; Central Andes ; Eastern Cordillera ; Cenozoic
    Language: English
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    Melt Production and Ejection From Lunar Intermediate‐Sized Impact Craters: Where Is the Molten Material Deposited? (2022)
    Details
    Publication Date: 2022-12-10
    Description: Differently aged impact melt in lunar samples is key to unveiling the early bombardment history of the Moon. Due to the mixing of melt products ejected from distant craters, the interpretations of the origin of lunar samples are difficult. We use numerical modeling for a better quantitative understanding of the production of impact‐induced melt and in particular its distribution in ejecta blankets for lunar craters with sizes ranging from 1.5 to 50 km. We approximate the lunar stratigraphy with a porosity gradient, which represents the gradual transition from upper regolith via megaregolith to the solid crustal material. For this lunar setting, we quantify the melt production relative to crater volume and derive parameters describing its increasing trend with increasing transient crater size. We found that about 30%–40% of the produced melt is ejected from the crater. The melt concentration in the ejecta blanket increases almost linearly with distance from the crater center, while the thickness of the ejecta blanket decreases following a power law. Our study demonstrates that if in lunar samples the concentration of a melt with a certain age is interpreted to be of a nonlocal origin, these melts could be the impact products of a large crater (〉10 km) located hundreds of kilometers away.
    Description: Plain Language Summary: Lunar samples contain abundant impact‐induced melt that crystallized at different ages. The melt ages record the formation time of its source craters and are key for a better understanding of the lunar bombardment history. In samples, there is not only the melt derived from the sampling region but also some that originate far away by being entrained in the ejecta of distant craters. Recognizing the distant‐derived melt is essential for the more credible sample interpretation, which requires knowledge of the melt distribution in the ejecta. We use numerical modeling to quantify the production of impact‐induced melt and in particular its distribution in ejecta blankets for lunar craters. We found that the melt concentration in the ejecta blanket increases with distance from the crater center. If the concentration of distant‐derived melt of a certain age in lunar samples is rather high (〉30%), it could originate from large craters (〉10 km) located hundreds of kilometers away.
    Description: Key Points: The melt concentration in the ejecta blanket increases almost linearly with distance from the crater center. Near‐surface porosity causes an increase in melt production. Due to decreasing porosity with depth, it is more prominent at small craters. The melt concentration in distal ejecta of crater of 10's km is rather high (〉30%).
    Description: Deutsche Forschungsgemeinschaft DFG http://dx.doi.org/10.13039/501100001659
    Keywords: ddc:523 ; lunar craters ; melt production ; numerical modeling
    Language: English
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    The role of repositories and data journals for Open Science (2022)
    Details
    Publication Date: 2022-11-29
    Description: Knowledge sharing in academia has been considered indispensable and is becoming a priority in most European funding schemes. Although we are already quite familiar with the different possibilities to publish our results in open-access journals, open science means way more than that. Open science aims at opening up research processes and granting access to research outputs to researchers, professionals and amateur scientists. There are different ways to ensure the storage and reusability of our data, making it available to other scientists. Furthermore, most of the scientific disciplines migrate their analyses to open-source environments (e.g., R, Phyton). However, tons of code produced remain stored in our personal computers either because we do not know the appropriate tools to share them with our colleagues or because we believe that it is not well structured. In this short course, you would learn how to establish links between publications, data, software and methods. Hence, we will discuss with our experts: i) the options to share our data and code with other peers, ii) obtain some tips to better organize our scripts, and iii) uncover potential barriers to sharing research and discuss possible solutions.
    Description: DFG, SUB Göttingen, GFZ Potsdam
    Description: presentation
    Keywords: ddc:550 ; Repository ; Data Management ; Open Science
    Language: English
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    FID GEO: Promoting Open Science in the Geosciences (2022)
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    Publication Date: 2022-11-29
    Description: The rise of Open Science practices is impacting the entire scientific publishing culture. The transition to Open Access for text publications goes hand in hand with the growing demand to make scientific data and software available to the general public. The FAIR data principles play a key role in this, designed to make research and the underlying data easily findable, accessible, interoperable, and reusable for humans and machines. Geosciences data are as diverse as their content. They range from large real-time data streams of international observing networks to small data sets produced by individual researchers at their laboratories. Consequently, there need to be different strategies for data management and publication in which research data repositories can be important partners for the researchers. The Specialised Information Service for Geoscience (FID GEO) is a DFG-funded project that is promoting a holistic approach of Open Science that includes scholarly literature, data, samples, and scientific software equally and pushes for their interlinkage. FID GEO has become an important player for connecting researchers, data repositories, information infrastructures, German geoscientific societies, and publishers. FID GEO actively provides data and text publishing services through its affiliated repositories GFZ Data Services and GEO-LEOe-docs, as well as on-demand digitization of printed geoscience literature and maps. In addition, FID GEO aims to inform the German-based geoscience community about all aspects of Open Science and FAIR data by bringing the discussions to the individual disciplines through various communication channels.
    Description: DFG, SUB Göttingen, GFZ Potsdam
    Description: http://doi.org/10.5194/egusphere-egu22-13354
    Description: presentation
    Keywords: ddc:550 ; Open Science ; Geoscience
    Language: English
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    FID GEO: promoting cultural change towards Open Access and FAIR data in the German geoscientific communityZ Data Services – A domain repository for geosciences data (2022)
    Details
    Publication Date: 2022-11-29
    Description: The rise of Open Science practices is impacting the entire scientific publishing culture. The transition to Open Access for text publications goes hand in hand with the growing demand to make scientific data and software available to the general public. The FAIR data principles play a key role in this, designed to make research and the underlying data easily findable, accessible, interoperable, and reusable for humans and machines. Geosciences data are as diverse as their content. They range from large real-time data streams of international observing networks to small data sets produced by individual researchers at their laboratories. Consequently, there need to be different strategies for data management and publication in which research data repositories can be important partners for the researchers. The Specialised Information Service for Geoscience (FID GEO) is a DFG-funded project that is promoting a holistic approach of Open Science that includes scholarly literature, data, samples, and scientific software equally and pushes for their interlinkage. FID GEO has become an important player for connecting researchers, data repositories, information infrastructures, German geoscientific societies, and publishers. FID GEO actively provides data and text publishing services through its affiliated repositories GFZ Data Services and GEO-LEOe-docs, as well as on-demand digitization of printed geoscience literature and maps. In addition, FID GEO aims to inform the German-based geoscience community about all aspects of Open Science and FAIR data by bringing the discussions to the individual disciplines through various communication channels.
    Description: DFG, SUB Göttingen, GFZ Potsdam
    Description: presentation
    Keywords: ddc:550 ; Open Science ; Geoscience
    Language: English
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    GFZ Data Services – A domain repository for geosciences data (2022)
    Details
    Publication Date: 2022-11-29
    Description: FZ Data Services is a domain repository for geosciences data comprising the Earth, Space and Environmental Sciences. It assigns digital object identifier (DOI) to data and scientific software since 2004. Hosted at the GFZ German Research Centre for Geosciences (GFZ), the repository has a focus on the curation of long-tail data by domain scientists on one hand, but also provides DOI minting services for several global monitoring networks/observatories in geodesy and geophysics and collaborative projects. Furthermore, as Allocating Agent for the International Generic Sample Number (IGSN), the globally unique persistent identifier for physical samples, GFZ is providing IGSN minting services for physical samples. GFZ Data Services increases the interoperability of long-tail data through (1) the provision of comprehensive domain-specific data description via standardised and machine-readable metadata with controlled domain vocabularies. Metadata is (2) complemeted with comprehensive and standardised technical data descriptions or reports; and (3) by embedding the research data in wider context by providing cross-references through Persistent Identifiers (DOI, IGSN, ORCID, Fundref) to related research products (text, data, software) and people or institutions involved. In addition to the task as a research data publisher, GFZ Data Services is the central node for research data management at the GFZ with information on metadata, data formats, the data publication workflow, FAQ, links to different versions of our metadata editor and downloadable data description templates. Specific data publication guidance is complemented by more general information on data management, like a data management roadmap for PhD students.
    Description: GFZ Potsdam
    Description: presentation
    Keywords: ddc:550 ; Data Management ; Repository
    Language: English
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    How to publish Open Access in the earth sciences (2020)
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    Publication Date: 2022-11-29
    Description: Open Access to scientific literature and research data has significant advantages for researchers as well as for society as a whole. Researchers might gain from increased citation rates and from higher visibility of their research outputs, while researchers as well as the public benefit from a better accessibility of scientific literature and data. Increasingly, funding organisations such as the European Commission in the context of Horizon 2020-funded projects or the 16 national and international members of “Plan S” demand that publications that result from projects funded by them are made openly accessible. The poster outlines the different ways of publishing text and data in Open Access. After a brief overview of reasons for publishing Open Access, it points out different routes for publishing texts in Open Access (in Open-Access-Journals or self-archiving) and major aspects for FAIR and open data publication.
    Description: DFG, GFZ Potsdam
    Description: poster
    Keywords: ddc:550 ; Open Access
    Language: English
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    The Specialised Information Service for Geosciences (FID GEO): Supporting Open Access Publications for the Geosciences Community in Germany (2022)
    Details
    Publication Date: 2022-11-29
    Description: The shift towards Open Science practices is increasingly demanded by science policy. The transition to Open Access for text publications goes hand in hand with a growing demand to make data, scientific software and samples, freely and FAIRly available to the general public. A persistent problem here is the clear and permanent accessibility and re-usability of scientific publications. This development affects both the scientific publication culture as well as the information infrastructures and poses major challenges to the German- based geosciences community. The specialized information service for geosciences (FID GEO) is a service funded by the German Research Foundation (DFG) and supports the cultural change towards Open Access publications. Hereby, FID GEO pursues a holistic approach to Open Science, including scientific literature, data, samples, and scientific software, and aims to promote their interconnection. FID GEO actively provides data and text publishing services through the affiliated repositories GFZ Data Services and GEO-LEOe-docs, as well as an on-demand digitization service of printed geoscientific literature and maps. The focus here is on the services and information systems that ensure permanently available and reliably citable publications of writings and data. Specifically, the service for text publications is provided in the FID GEOs own subject repository GEO-LEOe- docs. The affiliated research data repository GFZ Data Services is available for the publication of research data and scientific software from the earth and environmental sciences. In addition, FID GEO aims to comprehensively inform the German-based geoscientific community about Open Science and FAIR data by bringing the discussions to the individual disciplines through various communication channels. To strengthen the open information culture in the geosciences, FID GEO collaborates with strategic (inter)national initiatives such as NFDI4Earth, COPDESS and OneGeochemistry.
    Description: DFG, SUB Göttingen, GFZ Potsdam
    Description: poster
    Keywords: ddc:550 ; Open Access
    Language: English
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    Data Management: open, FAIR, citable? (2021)
    Details
    Publication Date: 2022-11-29
    Description: i-EDDA-Research School (BGR Spandau); i-EDDA = Innovative Exploration Drilling and Data Acquisition, https://www.iedda.eu/ ; Datenmanagement Workshop: 05.11.2021
    Description: DFG, GFZ Potsdam
    Description: presentation
    Keywords: ddc:550
    Language: English
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    Open Science – more than Open Access (2022)
    Details
    Publication Date: 2022-11-29
    Description: The Berlin Declaration from 2003 was the starting point for Open Access to scholarly publications. Today, however, we speak about Open Science that reaches far beyond Open Access and represents collaborative, transparent and accessible research that includes all kinds of research results: scholarly literature, research data, software, samples, instruments, etc. In addition, efforts such as the FAIR Principles and the Enabling FAIR Data Commitment Statement, combined with increasing demands for machine accessibility to data, have raised user expectations towards the capabilities of research data repositories and datacentres. These repositories are often key partners supporting researchers in fulfilling the new requirements. This presentation will draw the line from major statements and requirements of Open Science, delineate the role of research data repositories as well as major research infrastructures, like the fNFDI4Earth or EPOS (European Plate Observing System) are additional players in making research data accessible in harmonised form.
    Description: DFG, SUB Göttingen, GFZ Potsdam
    Description: presentation
    Keywords: ddc:550 ; Data ; Open Science
    Language: English
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    How open is our research? A discussion on the state of Open Science in the field of mineralogy and petrology (2022)
    Details
    Publication Date: 2022-11-29
    Description: How open is our research? A discussion on the state of Open Science in the field of mineralogy and petrology. Vortrag bei der Arbeitsgruppe Mineralogie+Petrologie der Uni Potsdam, 29.04.2022 A brief look at current trends toward an open science with a focused look at the state of the art in mineralogy and petrology. Followed by a discussion on how research in mineralogy and petrology can become more open.
    Description: DFG, GFZ Potsdam
    Description: presentation
    Keywords: ddc:550 ; Open Access
    Language: English
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    Wind Turbine Noise Reduction from Seismological Data (2021)
    Details
    Publication Date: 2022-12-01
    Description: Over the last years, installations of wind turbines (WTs) increased worldwide. Owing to negative effects on humans, WTs are often installed in areas with low population density. Because of low anthropogenic noise, these areas are also well suited for sites of seismological stations. As a consequence, WTs are often installed in the same areas as seismological stations. By comparing the noise in recorded data before and after installation of WTs, seismologists noticed a substantial worsening of station quality leading to conflicts between the operators of WTs and earthquake services. In this study, we compare different techniques to reduce or eliminate the disturbing signal from WTs at seismological stations. For this purpose, we selected a seismological station that shows a significant correlation between the power spectral density and the hourly windspeed measurements. Usually, spectral filtering is used to suppress noise in seismic data processing. However, this approach is not effective when noise and signal have overlapping frequency bands which is the case for WT noise. As a first method, we applied the continuous wavelet transform (CWT) on our data to obtain a time-scale representation. From this representation, we estimated a noise threshold function (Langston & Mousavi, 2019) either from noise before the theoretical P-arrival (pre-noise) or using a noise signal from the past with similar ground velocity conditions at the surrounding WTs. Therefore, we installed low cost seismometers at the surrounding WTs to find similar signals at each WT. From these similar signals, we obtain a noise model at the seismological station, which is used to estimate the threshold function. As a second method, we used a denoising autoencoder (DAE) that learns mapping functions to distinguish between noise and signal (Zhu et al., 2019). In our tests, the threshold function performs well when the event is visible in the raw or spectral filtered data, but it fails when WT noise dominates and the event is hidden. In these cases, the DAE removes the WT noise from the data. However, the DAE must be trained with typical noise samples and high signal-to-noise ratio events to distinguish between signal and interfering noise. Using the threshold function and pre-noise can be applied immediately on real-time data and has a low computational cost. Using a noise model from our prerecorded database at the seismological station does not improve the result and it is more time consuming to find similar ground velocity conditions at the surrounding WTs.
    Description: poster
    Keywords: ddc:550
    Language: English
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    Reprocessing of the hessian DEKORP seismic profiles (2021)
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    Publication Date: 2022-12-01
    Description: As part of the German continental seismic reflection program (Deutsches Kontinentales Reflexionsseismisches Programm, DEKORP), three large seismic traverses (with the sub-profiles: DEKORP'84-2S and '86-2N; DEKORP'88-9N; DEKORP'90-3A and '90-3B) were measured in the state of Hesse in Germany. The main research topic of DEKORP were deep seismic studies to investigate the lithospheric structure beneath Germany. Thus, for acquisition, strong sources were used to image in these depths, resulting in an excellent S/N ratio, but the main focus was not on the uppermost kilometres. From today's perspective, however, this depth range is of great interest for a wide range of possible technical applications (including medium-deep and deep geothermal projects). The DEKORP profiles cover approx. 450 km in the state of Hesse and mostly cross areas where only insufficient geological data exist (i.e. only few deep boreholes). In order to close or reduce these knowledge gaps, these DEKORP lines were reprocessed in 2019/20. The focus of the reprocessing was on improving the resolution / mapping of geological structures down to a depth of 6 km (approx. 3 s TWT) to describe the prolongation of faults and geological structures in more detail than in previous studies. Nevertheless, deeper structures were also reinterpreted and compared to previous interpretations. The results were directly incorporated into the new geological 3D model of the state of Hesse, developed by the Technical University of Darmstadt (Hessen3D 2.0, BMWi-FKZ: 0325944). In order to achieve these goals and in view of the fact that today's processing methods have improved considerably compared to the 1990‘s, a state-of-the-art reprocessing was applied for all DEKORP profiles traversing the state of Hesse. In comparison to the original processing, additional processing steps like CRS instead of CDP stacking, turning-ray tomography and prestack depth migration were carried out. We present exemplary results of the reprocessing as well as initial geological reinterpretations for the profile DEKORP'88-9N.
    Description: poster
    Keywords: ddc:550 ; DEKORP ; Reprocessing of 2D seismic profiles ; Hesse ; Upper Rhine Graben ; DEKORP'88-9N
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    Numerical analysis of gravity and magnetic fields prior to structural modelling (2021)
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    Publication Date: 2022-12-01
    Description: The work presented here is part of ongoing studies in the AlpArray initiative and the priority program "MB-4D" regarding the modelling of the lithosphere in the Ligurian Sea (northwestern Mediterranean Sea). It will be based on constraining data from LOBSTER and LISA campaigns of past GEOMAR projects and a study in our research group at CAU Kiel. Our motivation is the combination and interdisciplinary interpretation of independent information from geology, tectonics, geophysics, and petrology. The existing gravity fields, especially the new compilation of the AlpArray Gravity Research Group (AAGRG) is considered as database (high resolution Free Air- and Bouguer anomalies) and the isostatic residual field, besides data of the ICGEM Potsdam (disturbance) and the ESA GOCE gradients for gravity and data for the magnetic field anomaly. The gravity and magnetic fields are analyzed using Euler deconvolution with regularization (R. Pašteka, Comenius University Bratislava) and application of curvature analysis we use both, the fields themselves and their gradients. Besides the calculation of the so-called "3rd derivative" of the gravity potential, we also investigate a possible use of the invariants of the gravity field based on gradient data and compare and correlate the results with structural and tectonic maps in the area of the Ligurian Sea and the adjacent French and Italian mainland. The findings from these comparisons will later be used to initiate the compilation of 3D density and susceptibility models for the studied region.
    Description: poster
    Keywords: ddc:550 ; Gravity gradients, ; curvature gravity field ; Gravity invariants ; Ligurean Sea
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    Induced micro seismicity due to raising mine water level in former coal mines in the eastern Ruhr area (Germany) (2021)
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    Publication Date: 2022-12-01
    Description: FloodRisk is an interdisciplinary project focusing on the effects of mine water level rise in bandoned coal mine regions in Germany. Such effects are heterogeneous ground uplift, stress changes due to the change in pore pressure and the reactivation of potential faults. One of the most directly measurable effects is certainly the induced micro seismicity. It is known from previous studies that the flooding of old mines can lead to a renewed increase level in induced micro seismicity in these regions. In this study the relationship between mine water rise, fluid-induced stress changes and induced seismicity in the Haus Aden dewatering area in the eastern Ruhr area (Germany) will be investigated in more detail. For this purpose, we operate a network of currently 21 short period seismic stations in the region of the former "Bergwerk Ost" colliery, which had the highest seismicity rate in the Ruhr area during active underground coal mining. This network is still to be expanded to cover the entire water drainage area, about 30 Raspberry Shake sensors are waiting for the possibility of installation. Nevertheless, the existing network registered almost 1000 induced micro seismic events in a magnitude range from -0.7 up to 2.6 MLv. Many of these events are spatially clustered and some show quite high waveform similarity. This allows relative localisation and can increase the accuracy of the location. The depth location of the earthquakes, within the limits of localisation accuracy, agrees very well with the distribution of seismicity at the time of active mining. The spatial distribution so far seems to be limited by a large inactive transverse fault in the west. It needs to be clarified what influence this fault has on the propagation of mine water in the underground. The measured temporal trend of the mine water level, after pumps were shut down in mid-2019, shows a strong correlation with the temporal evolution of the observed micro seismicity. In the first months after the pumps are switched off, the water levels at the observation points rise only slowly and isolated microseismic events occur again. In November 2019, the rise in water levels doubled and at the same time, the strongest induced event in the measurement period was recorded with a magnitude of 2.6 MLv . In the following months, the seismicity rate ranged from 8 to 34 events above 0.5 MLv per month, some of which were felt.
    Description: Bundesministerium für Bildung und Forschung
    Description: poster
    Keywords: ddc:550 ; induced microseismicity ; FloodRisk ; waveform similarity ; raising mine water level
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    Interdisciplinary 3D potential field modelling of complex lithospheric structures by IGMAS+ (2021)
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    Publication Date: 2022-12-01
    Description: We introduce an approach for 3D joint interpretation of potential fields and its derivatives under the condition of constraining data and information. The interactive 3D gravity and magnetic application IGMAS (Interactive Gravity and Magnetic Application System) has been around for more than 30 years, initially developed on a mainframe and then transferred to the first DOS PCs, before it was adapted to Linux in the ’90s and finally implemented as a cross-platform Java application with GUI. Since 2019 IGMAS+ is maintained and developed in the Helmholtz Centre Potsdam – GFZ German Research Centre by the staff of Section 4.5 – Basin Modelling and ID2 – eScience Centre. The core of IGMAS+ applies an analytical solution of the volume integral for the gravity and magnetic effect of a homogeneous body. It is based on the reduction of the three-folded integral to an integral over the bounding polyhedrons that are formed by triangles. Later the algorithm has been extended to cover all elements of the gravity tensor as well and the optimized storage enables fast leastsquares inversion of densities and changes to the model geometry and this flexibility makes geometry changes easy. Because of the triangular model structure of model interfaces, IGMAS can handle complex structures (multi- Z surfaces) like the overhangs of salt domes and variable densities due to voxelization. To account for the curvature of the Earth, we use spherical geometries. Therefore IGMAS+ is capable to handle models from big-scale to regional and small-scale models (meters) used in Applied Geophysics.
    Description: poster
    Keywords: ddc:550 ; Potential field modelling ; Complex modelling ; Visualization ; Software development
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    Inverse and forward gravity modeling for revealing the crustal structure of Volga-Uralian subcraton (2021)
    Details
    Publication Date: 2022-12-01
    Description: A new crustal model of the Volga-Uralian subcraton was built. The compilation of the model was subdivided in two steps: (1) inverse gravity modeling followed by (2) thorough forward gravity modeling. For inverse gravity modeling GOCE gravity gradients were used. The effect of the Earth sphericity was taken into account by using tesseroids. Density contrasts between crust and mantle were varied laterally according to the tectonic units present in the region. The model is constrained by the available seismic data including receiver function studies, and deep reflection and refraction profiles. The Moho discontinuity obtained during the gravity inversion was consequently modified, and complemented by the sedimentary cover, upper crust, lower crust, and lithospheric mantle layers in the process of forward gravity modeling. Obtained model showed crustal thickness variation from 34 to more than 55 km in some areas. The thinnest crust with the thickness below 40 km appeared on the Pericaspian basin with the thickest sedimentary column. A relatively thin crust was found along the central Russia rift system, while the thickest crust is located underneath Ural Mountains as well as in the center of the Volga-Uralian subcraton. In both areas the crustal thickness exceeds 50 km. At the same time, the gravity misfit of ca. 95 mGal between the measured Bouguer gravity anomaly and forward calculated gravity field was revealed in the central area of the Volga-Uralian subcraton. This misfit was interpreted and modeled as high-density lower crust which can possibly represent an underplated material. In the end, the new crustal model of Volga-Uralian subcraton respects the gravity and seismic constraints, and reflects the main geological features of the region. This model will be used for further geothermal analysis of the area.
    Description: poster
    Keywords: ddc:550 ; Crustal model ; Gravity ; Inversion ; Volgo-Uralia ; Tesseroids ; Moho
    Language: English
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    19th September: a date marked by earthquakes in Mexico City (2021)
    Details
    Publication Date: 2022-12-01
    Description: poster
    Keywords: ddc:550
    Language: English
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  • 52
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    Regional probabilistic seismic hazard assessment in Bangladesh (2021)
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    Publication Date: 2022-12-01
    Description: This presentation summarizes input data, procedures and results of probabilistic seismic hazard assessment (PSHA) in Bangladesh in the framework of the project ‘Geo information for Urban Planning and Adaptation to Climate Change’. It is a cooperation of the Geological Survey of Bangladesh (GSB) and the Federal Institute for Geosciences and Natural Resources (BGR) of Germany. The main aim of the project is to provide city planners with “Ground Suitability Maps”, which display different geo-factors. Seismic hazard is one of the geo-factors that contributes to these maps. For the derivation of “Ground Suitability Maps”, the influence of the local underground conditions will be taken into account additionally. A major part of Bangladesh is located in earthquake prone regions due to active tectonics. The Indian plate moves north-eastward towards the Eurasian plate at a velocity of about 6 cm/year. This motion leads to thrusting to the north (Himalaya) and to subduction to the east together with strike-slip mechanism. The thrusting and subduction processes have caused large historical earthquakes even inside Bangladesh (e.g. 1885 Bengal Earthquake M7 and 1918 Srimangal Earthquake M7.6). Therefore, it is crucial to assess seismic hazard in urban planning in Bangladesh. The input databases were compiled from the literature, reviewed and evaluated in this study. These are earthquake catalogs, the distribution of active faults and ground motion prediction equations. The most consistent and reliable databases were selected to be used in PSHA. The data of the earthquake catalog were declustered to eliminate the duplicated events, aftershocks and foreshocks. The spatial distribution of areal seismic sources was characterized using the distributions of earthquakes in the catalog and active faults. The completeness analysis of the earthquake catalog was performed and the Gutenberg-Richter magnitude recurrence distribution was derived for each seismic source. The results of PSHA are presented in the form of peak ground acceleration (PGA) maps with 10% exceedance probability in 50 years. As usual in regional PSHA, the results were compiled assuming bedrock as underground condition (so-called engineering bedrock with shear velocity of Vs30≥760 m/s). The northern and eastern parts of Bangladesh show the highest seismic hazard with PGA around 0.4 g with 10% exceedance probability in 50 years. This observation was expected because of the active tectonics in these parts.
    Description: poster
    Keywords: ddc:550
    Language: English
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    New Small Aperture Broadband Arrays in the European Arctic (2021)
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    Publication Date: 2022-12-01
    Description: As part of the EPOS-Norway infrastructure project, NORSAR received funding from the Research Council of Norway for a new regional seismic array on Bjørnøya (Bear Island) in the European Arctic. After along planning phase, a six-element broadband array was installed by NORSAR staff in August 2019 and has been providing data to NORSAR in near real-time since then. Due to several logistical and administrative constraints the 6-element array has an aperture of only 300 m. All sites are equipped with Kinemetrics MBB-2 sensors and Earth Data EDR-209 digitizers that are installed in near-surface vaults. Data are automatically copied to the Norwegian node of the European Integrated Data Archive (EIDA) and are openly available. Due to environmental restrictions less than the planned 9 array sites could be installed on Bjørnøya and the non-used instruments are now available to extend the broadband station Hornsund (HSPB), Southern Spitsbergen, to another small aperture broadband array, also with 6 sites. The array installation had to be postponed because of the ongoing pandemic and is now planned for the Arctic summer 2021.
    Description: poster
    Keywords: ddc:550
    Language: English
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  • 54
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    Seismotectonic regions in Germany and adjacent areas - Concept and results (2021)
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    Publication Date: 2022-12-01
    Description: Seismotectonic regions are a basic input in seismic hazard assessment. Several seismotectonic zonations for Germany have been proposed in the past. We have developed a new regionalization based on the definition in the German Nuclear Safety Standard: “A seismotectonic unit is a region for which uniformity is assumed regarding seismic activity, geological structure and development and, in particular, regarding neotectonic conditions”. Our new concept aims for transparent implementation of geological criteria, which we initially analyze separately from seismicity. We strive for a better documentation and justification of the geological elements used to delimit seismotectonic regions, based on an analysis of the geological evolution in six time slices from the Permian (300 Ma) to the Present. The time slices are separated by marked changes in the tectonic regime and associated with the development of new fault systems or reactivation of existing ones. The present-day fault network comprises faults from all time slices. For each time slice, a subset of active faults has been extracted based on geological evidence for fault activity at that time. Uncertainties of these age assignments are documented. The fault subsets delimit regions of different strain intensity. The superposition of strain intensity distributions across all time slices identifies regions affected by polyphase deformation and regions nearly undeformed over geological time, potentially indicating areas of increased or reduced present-day seismic hazard. Our new zonation consists of fewer regions than earlier ones. The geological zonation correlates well with recent seismicity in areas of Cenozoic rifting and reasonably well with less frequent earthquakes in a belt affected by Mesozoic extension and contraction. However, a few stronger earthquake cluster in regions of low geological strain. The most prominent earthquake clusters (Swabian Jura, Vogtland / NW Bohemia) also defy a simple correlation with known geological structures.
    Description: poster
    Keywords: ddc:550
    Language: English
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  • 55
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    Delamination Detection on a Concrete Bridge Deck Using Fast Scanning Impact Echo (2021)
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    Publication Date: 2022-12-01
    Description: poster
    Keywords: ddc:550
    Language: English
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  • 56
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    Constructing and validating a large-scale velocity-model for the North German Basin in Schleswig-Holstein and Hamburg – A part of the joint project TUNB (2021)
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    Publication Date: 2022-12-01
    Description: As a result of the joint project ‘Subsurface Potentials for Storage and Economic Use in the North German Basin’ (German acronym: TUNB) the Geological Surveys of Northern Germany and the Federal Institute for Geosciences and Natural Resources (BGR) finalized a coherent geological 3D-model of the deep subsurface of the North German Basin in early 2021. The model consists of 13 major base surfaces from Oligocene to Zechstein, fault surfaces and hull surfaces of salt diapirs. In the northwestern part it is based on the datasets of the Tectonic Atlas of NW-Germany (GTA) along with well and seismic data from the hydrocarbon industry. Additionally to modelling the onshore part of Schleswig-Holstein and Hamburg and insuring cross-border consistency to the neighboring federal states, the Geological Survey of Schleswig-Holstein (LLUR) reconstructed a 3D-large-scale velocity model based on previous work from Jaritz et al. (1991). Their velocity approach was developed within the GTA-project and is based on sonic-log and check-shot-velocities. It assumes a linear velocity increase, which is calculated from specific global gradients for different major lithostratigraphic layers and laterally varying starting-velocities. To validate the constructed 3D-velocity-model, its velocities were compared to velocities measured at boreholes by oil and gas companies. In general, a good agreement was found between modeled and measured data (deviation 〈 5%), in which the average velocities seemed to resemble the check-shot data more accurately than the interval velocities the sonic-log-measurements. In distinct locations, the velocity model was used to convert the newly constructed TUNB-horizons from the depth- to the time-domain in order to compare them to seismic sections. Whereas overall a good agreement between horizons and seismic reflectors was found, differences were identified especially in structural complex areas. Whether these can be attributed to earlier interpretations from the GTA, the modelling of the horizons or insufficiencies in the velocity-model has yet to be determined. A follow-up project to the TUNB-project is anticipated to start in early summer 2021. The goal of the project is to derive a consistent velocity model over large parts of the North German Basin. Main challenges will be integrating available borehole and seismic data into existing velocity-modelling approaches with a special focus on establishing cross border consistency to eastern federal states.
    Description: poster
    Keywords: ddc:550
    Language: English
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    CAYMAN: Characterizing the crust using 2D & 3D seismic tomographic methods. (2021)
    Details
    Publication Date: 2022-12-01
    Description: About 25% of the Earth’s mid-ocean ridges spread at ultraslow rates of less than 20 mm/yr. However, most of these ultraslow spreading ridges are located in geographically remote areas, which hamper investigation. Consequently, how the crust forms and ages at such spreading centres, which traditional models predict to be magma-starved and cold, remains poorly understood. One of the most accessible ultra-slow spreading centres is the Mid Cayman Spreading Centre (MCSC), in the Caribbean Sea, with spreading rates of ~15-17 mm/yr. CAYSEIS project was proposed to survey the Cayman Trough area in order to obtain new data that constraints the nature of the crust, tectonic structures, lithologies outcropping and hydrothermal processes taking place in this area. Understanding the sub-seabed geophysical structure of the MCSC is key to understanding not only the lithologies and structures exposed at the seabed, but more fundamentally, how they are related at depth and what role hydrothermal fluid flow plays in the geodynamics of ultraslow spreading. CAYSEIS was a joint and multidisciplinary programme of German, British and US American top tier scientists designed for the obtaining of a new high-quality dataset, including 3D Wide-Angle Seismic (WAS), magnetic, gravimetric and seismological data. During the CAYMAN project, we took leverage of the CAYSEIS dataset to invert a 3D tomographic model of the Cayman Trough lithosphere using the Tomo3D code (Meléndez et al., 2015; 2019). This is one of the first times that the Tomo3D code is used for 3D inversion of real datasets. Thus, we are checking our results comparing them with tomographic inversions of 2D lines and testing the different parameters to obtain the more accurate and higher resolution model as possible. The results of this experiment will show not only the lithospheric structure along and across the MSCS, including the exhumed Ocean Core Complexes in the surrounding areas, but the 3D lithospheric configuration of the region which is important to understand the crustal formation processes and the evolution of ultra-slow spreading settings.
    Description: Poster
    Description: poster
    Keywords: ddc:550 ; 3D tomography ; crustal characterization ; ultra-slow spreading ; Cayman Trough
    Language: English
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    Classifying infrasound signals at Mount Etna using pattern recognition techniques (2021)
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    Publication Date: 2022-12-01
    Description: The ongoing activity of Mount Etna and the proximity to the nearby population requires constant monitoring. Infrasound recordings play an important role in volcanic observation because explosive activity near or above ground as well as shallow tremor processes are easier to identify with airborne sound waves than with seismic waves that are significantly scattered and refracted in the volcano edifice. However, infrasound signals are often blurred by noise, in case of Mount Etna, mostly wind induced noise. manual distinction of noisy data from real volcanogenic signals brings along a considerable effort and requires expert knowledge. At Mount Etna five summit craters are currently known with fluctuating levels of activity. This leads to a wide variety of infrasound signal patterns interfered by changing noise levels. In order to distinguish waveforms of noise from signals of volcanic origin we apply unsupervised pattern recognition techniques. We show that by extracting features from the amplitude spectrum different infrasound regimes can be distinguished with Self-Organizing maps (SOMs). This technique provides an option to color-code the results for an intuitive interpretation and allows even for a more detailed recognition of transitional activity regimes. We create a reference data set from multiple months of infrasound waveforms to include as many activity regimes as possible to train the SOM. This enables a fast classification of new data.
    Description: poster
    Keywords: ddc:550 ; Infrasound ; Pattern Recognition ; Volcano Monitoring ; Etna
    Language: English
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    Monitoring Reinforced Concrete Structures with Coda Waves - The Influence of Temperature on Ultrasound Velocity Changes calculated with Coda Wave Interferometry (2021)
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    Publication Date: 2022-12-01
    Description: DFG FOR 2825
    Description: poster
    Keywords: ddc:550 ; Ultrasound ; Coda Wave Interferometry ; Bridge Monitoring
    Language: English
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  • 60
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    Seismic reflection character of the plate interface in the rupture zone of the 2014 Iquique earthquake sequence (2021)
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    Publication Date: 2022-12-01
    Description: poster
    Keywords: ddc:550
    Language: English
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  • 61
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    Computational Modelling of Coupled Heat Transport between the Heterogeneous Earth and an Overlying Ice Sheet (2021)
    Details
    Publication Date: 2022-12-01
    Description: Due to a complex interplay between the Earth and overlying ice sheets, a large variety of subglacial landforms developed. One example is the in the North German Basin widely spread phenomenon of tunnel valleys. An observed correlation to underlying salt structures is often explained mechanically. We focus on an alternative hypothesis based on thermodynamic processes: As salt better conducts heat than the surrounding rocks, the geothermal heat flux is augmented above salt structures. This leads to melting processes at the interface between the Earth and the ice sheet. The subglacial rivers finally erode the tunnel valleys. To test this hypothesis, we model related hydrothermal processes by means of a finite-difference open-source code (SHEMAT-Suit). The model accounts for heat conduction, groundwater flows, processes in the glaciothermal system such as the motion and spatiotemporal temperature evolution within the ice, and finally the coupling of both at the subglacial interface to account for the feedback mechanisms. Glaciothermal system and coupling processes are incorporated based on an idealized 1D model for the ice cover. We present a scaling analysis to discuss dominant processes. Our results show that a purely conductive subsurface (complete absence of groundwater flow) leads to a very moderate increase of the geothermal heat flux above salt structures. This implies a slight increase of the melting rates, which by itself is not enough to trigger tunnel valley erosion. Additional hydrothermal flows e.g. through fault zones may increase the subglacial melting rates. In this contribution, we will present results from a case study in the Southern North Sea. A 2D seismic section includes two tunnel valleys above salt structures. To model the state prior to erosion and sedimentation during and after the Quaternary glaciations, the Quaternary strata is replaced by strata with the same physical properties and thicknesses than the Paleocene to Miocene strata. Simulation runs with SHEMAT-Suite calculated the subsurface temperature distribution and the geothermal heat flux distribution at the subglacial interface. This allows assessing the subglacial melting rates along with the temperature profile within the ice cover for a number of glaciation scenarios. Current results show that thermodynamic processes reinforce the formation of tunnel valleys together with e.g. mechanical weakening by faulting.
    Description: poster
    Keywords: ddc:550
    Language: English
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  • 62
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    Archaeogeophysical investigation at Neuss-Norf, Germany (2021)
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    Publication Date: 2022-12-01
    Description: A combination of noninvasive geophysical magnetic gradiometery and electrical resistivity tomography (ERT) was employed to locate the remains of an old church form the 9th century in Neuss-Norf, Germany. The gradiometery survey was carried out along 27 parallel profiles oriented approximately E–W with a profile spacing of 1 m and a sampling spatial interval of 0.5 m along each profile in order to detect the distributions of the possible buried walls of the church and other related archaeological remains. The vertical gradient of the magnetic field, with a fixed distance of 1.04 m between the sensors, was measured. The lower sensor was fixed at a height of 0.32 m from the ground surface. The magnetic data were transferred to the frequency domain using Fast Fourier transform then reduced to the magnetic pole. The analytic signal and power spectrum techniques were applied to the obtained magnetic data. Moreover, ERT measurements were performed based on the results of the magnetic survey along 12 profiles utilizing the Wenner and Dipole-Dipole arrays with 0.5 m electrode spacing. The ERT data from both arrays were merged into one dataset to form a non-conventional mixed array. The ERT data were inverted into 2D resistivity models using robust (blocky) inversion technique, and then a 3D resistivity prospective was created. The combined interpretation of the magnetic and ERT showed that the archaeological structures are close to the ground surface with a maximum depth of up to 2 m. We successfully detected anomalous zones that could be associated with the walls of at least one ancient church-building in addition to several possible archaeological structures in the survey area. A considerable agreement between the results of both methods was observed. Highly magnetic sources that could be associated with metallic objects within tomb-like structures were detected. An archaeological map of the possible location of the old church and the assumed surrounding tombs and features was constructed. Finally, some promising places were suggested in order to start an archaeological excavation in the site based on the findings of our research.
    Description: poster
    Keywords: ddc:550 ; Archaeogeophysics; ERT; Magnetic gradiometery; Neuss-Norf, Germany
    Language: English
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    Vintage crustal-scale seismic profiling data made available for future applications: DEKORP 1984 – 1999 (2021)
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    Publication Date: 2022-12-01
    Description: The German continental seismic reflection program DEKORP (DEutsches KOntinentales Reflexionsseismisches Programm) was carried out in the years between 1984 and 1999. The aim of DEKORP was to investigate the deep crustal structure of Germany with high-resolution near-vertical incidence (mostly vibro)seismic acquisition, supplemented by wide-angle seismic and other target-oriented piggy-back experiments, all complemented by optimized methods of data processing and interpretation. The DEKORP project was an equivalent to many other deep-seismic programs world-wide such as COCORP, BIRPS, LITHOPROBE, ECORS, CROP, BELCORP, IBERSEIS and others. The resulting DEKORP database consists of approximately 40 crustal-scale 2D-seismic reflection lines covering a total of ca. 4 700 km and one 3D-seismic survey covering ca. 400 km², recorded in close connection with the German Continental Deep Drilling Program (KTB). Nowadays, re-recording of these seismic traverses in the same extent and quality would often not be possible anymore due to increased acquisition costs and tightened permission requirements. Therefore these datasets provide unique and deep insights into the subsurface below Germany covering the earth’s crust from the surface to the upper mantle. Currently, many of the original raw data are still stored on old storage media and in formats, which can only be read by special devices, programs and experts. To prevent the final loss of this valuable geoscientific treasure an initiative at GFZ transcripts all relevant DEKORP data to modern formats and media. Over the last few years the demand for DEKORP data continuously increased. Several academic institutions and commercial companies reprocess and/or reinterpret these data, which lead to significant improvements in the quality of the results. Fields of applications are geothermal development, hazard analysis, hydrocarbon/shale gas exploration, underground gas storage, tunnel construction, disposal of nuclear waste and more. To simplify the data access for the scientific as well as for the commercial geo-community, a well-structured provision and utilisation concept is being developed. The concept includes so-called data publications with DOIs, a defined license model and automised retrieval for each of the surveys providing raw data, processed data, meta data, related links and more. The plan aims to have all relevant DEKORP datasets compiled and prepared for access via web interface till 2022.
    Description: poster
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    Language: English
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    A new strategy for aeromagnetic survey merging and application to Greenland (2022)
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    Publication Date: 2022-12-01
    Description: Aeromagnetic surveys help us to learn about geology. To achieve good coverage, surveys need to be merged. However, conventional methods introduce long-wavelength bias and cannot handle the individual survey quality. We develop a new approach to process large aeromagnetic surveys with an equivalent layer approach and combine them with satellite data. To facilitate the usage of large data sets, we divide the study area into blocks and treat each block individually. We adjust the block size according to the resolution of the equivalent source model. Within each block we solve for equivalent sources using an iterative linear inversion with Tikhonov regularization. We apply a multi-resolution strategy by iteratively decreasing the dipole spacing, dipole depth and block size. In each step, the resolution is applied to the residual of the previous steps. This ensures both a good representation of the large and small-scale structures as well as reasonable computational costs. Advantages of the blockwise inversion are the handling with large data sets due to splitting up the study area and neglecting influences of sources above a certain distance. This reduces computational costs and still fits the data well in comparison with an unblocked inversion. Some structures cannot be resolved well with just one dipole layer, so the multi-resolution strategy enables to have a better fit by separating regional and local sources. For the final compilation, we replace the long wavelengths part of the aeromagnetic data with satellite data to spherical harmonic degree 110. We demonstrate our new approach with a newly compiled large data base for Greenland.
    Description: poster
    Keywords: ddc:550 ; aeromagnetic ; inversion ; greenland ; multi-layer
    Language: English
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    The European Arctic Seismic Bulletin for the years 1990 – 2013 (2022)
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    Publication Date: 2022-12-01
    Description: Recent years have shown an increased interest in Polar research and in particular in understanding tectonics and seismic hazard in the Arctic. To understand the seismic activity in the European Arctic, the seismic bulletins should be as complete as possible. We present a new seismic event bulletin for the European Arctic (70° – 90° N, -15° – 75° E), for the 24-year long period 1990 – 2013. The poster will show in detail the merging of the different sources taken in account for the compilation, the homogenization of the data and the relocation of the seismic events. With respect to the ISC bulletin for this region, the new bulletin contains 5,932 new seismic events and 54,630 new seismic onset readings from stations mostly located at regional distances. The gains are distributed over the entire study region, with the most significant contributions across the Svalbard Archipelago, along the Knipovich and northern Mohns Ridges, as well as northern Fennoscandia.
    Description: Norwegian Research Council Grant 233973/H30
    Description: Russian Foundation for Basic Research Grant 14-05-93080
    Description: Russian Foundation for Basic Research Grant 18-05-70018
    Description: https://doi.org/10.31905/TYLLQY8T
    Description: poster
    Keywords: ddc:550 ; European Arctic ; Seismic Bulletin
    Language: English
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    Testing the advantages of ultra-dense GPR antenna arrays for the Archaeological Prospection (2022)
    Details
    Publication Date: 2022-12-01
    Description: During the last few years, the use of Ground-Penetrating-Radar (GPR) multi-channel antenna arrays in the Archaeological Prospection increased dramatically. The main advantage of this type of survey is a much faster data acquisition combined with a dense profile spacing. However, most of the common multi-channel arrays consist of antennae with a spacing of not smaller than 8 cm. The aim of our test survey was to evaluate how an even denser spacing of 4 cm that is provided by the IDS Stream-C GPR device at a centre frequency of 600 MHz can improve the detection of small archaeological features. As a test site, we chose the Great Bath in Kempten-Cambodunum. This first capital of the Roman province Rhaetia never has been overbuilt in the following centuries and even today it is used as a grassland declared as an Archaeological Park. Already in 1911, the Great Bath was excavated and beside the walls of different building phases, also small features like a multitude of hypocaust pillars were unearthed. Hence, this building structure depicts an ideal test site and a 40x40m grid covering the main part of the construction was chosen for the application of the antenna array. As a comparison, the same grid was contemporaneously surveyed with a single antenna IDS Duo device (600 and 200 MHz) and a 50 cm profile spacing. Regarding the walls of the Roman bath, the two surveys show comparable results: both datasets represent the stone constructions of 50 – 90 cm width quite well. Furthermore, the depth slices of both devices provide a differentiation of the single building phases. Nevertheless, the resolution for the multi-channel antenna array is of course much higher due to the denser profile spacing. Huger differences occur for the hypocaust pillars of 25 cm lateral length. These features can be mapped in detail with the 4 cm profile spacing of the IDS Stream-C system. Whereas the IDS Duo can only resolve some of the hypocausts, a multitude of them gets visible between 70 and 110 cm depth in the Stream-C data. As a conclusion, it can be stated that standard archaeological remains like stone walls, for sure, can be surveyed with single antenna GPR devices in a common profile spacing of 50 cm. However, in case of the existence of faint archaeological features the application of ultra-dense antenna arrays like the IDS Stream-C is advisable to get a comprehensive overview of a site without the necessity to excavate them.
    Description: poster
    Keywords: ddc:550 ; Ground-Penetrating Radar ; GPR ; Multichannel Antenna Array ; Roman Bath ; Hypocaust Pillars
    Language: English
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    Induced microseismicity due to mine flooding - Observation, characterisation and relation to mine water rise in the eastern Ruhr area (2022)
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    Publication Date: 2022-12-01
    Description: The Floodrisk project takes a muti- and interdisciplinary look on the effects of the rise in mine water level in abandoned coal mine regions in Germany. Such effects are heterogeneous ground uplift, stress changes due to the pore pressure changes and the reactivation potential of faults. One of the most directly measurable effects is the induced seismicity. It is known from previous studies that the flooding of old mines can lead to a renewed increase in induced microseismicity in these regions. We focused on the observation of the eastern Ruhr area and investigate in detail the relationship between mine water rise and induced seismicity in the Haus Aden dewatering area. For this purpose, we operate a network of up to 30 short period seismic stations in the region of the former "Bergwerk Ost" colliery, which had the highest seismicity rate in the Ruhr area during active mining. Continuous monitoring of seismicity and mine water levels is available for this region from the active mining phase, through the post-mining phase to flooding. Since the beginning of the flooding, more than 20000 onsets were picked and over 1700 induced events were localised in a magnitude range from -0.7 up to 2.6 MLv. For some larger events, focal mechanisms could be determined. The spatial distribution of hypocentres is divided into two areas, with few events in the central study area and over 95% of earthquakes in its eastern part. Many of these events are spatially clustered and some show quite high waveform similarity. This allows relative localisation to increase the accuracy of the location. Comparing the old galleries,which today serve as the main underground waterways, with the localisations from the relative localisation, strong correlations can be seen. The measured temporal trend of the mine water level, after pumps were shut down in mid-2019, shows a strong correlation with the temporal evolution of the observed micro seismicity. In the first months after the pumps are switched off, the water levels at the observation points rise only slowly and isolated microseismic events occur again. In November 2019, the rise in water levels doubled and at the same time, the strongest induced event in the measurement period was recorded with a magnitude of 2.6 MLv. In the years 2020, 2021 66 and 58 events 〉= MLv 1 were observed, respectively. In contrast to this number only 2- 9 events 〉= MLv 1 per year were observed in the post-minig phase before flooding.
    Description: Bundesministerium für Bildung und Forschung
    Description: poster
    Keywords: ddc:550 ; induced seismicity ; post mining ; mine water rise ; Ruhr Area
    Language: English
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    Large-scale UAV magnetometryon a former World War II airfield at Ganacker(Lower Bavaria, Germany) (2022)
    Details
    Publication Date: 2022-12-01
    Description: In the last few years, several Unmanned Aerial Vehicle (UAV) based magnetometer systems have been tested for archaeological prospection. Due to their higher sensitivity, scalar magnetometers have been preferred as test sensors. However, total field magnetometer are vulnerable to disturbances, especially those generated by the UAV itself. Therefore, most UAV scalar magnetometer systems use the method of increasing the distance between magnetic sensors and the UAV to reduce interference. But freely suspended sensors tend to swing on ropes under the UAV and can produce data that are strongly influenced by heading errors. For our test, we therefore chose the UAV-fixed, compact setup of the SENSYS MagDrone R4, which is equipped with five three-axis FGM3D/75 fluxgate sensors at 50 cm spacing and is covering a swath width of 2.5 m. The 200Hz sampling rate of the R4 allows easy filtering of interference generated by the UAV and external disturbances like power lines or infrastructure. Magnetograms with a spatial resolution of up to 0.20 m per pixel were produced from the data. At Ganacker, we chose the former infrastructure core of the World War II German Air Force airfield as a test site. A wide range of archaeological structures and features with high magnetic contrast were expected on this area. The test site is currently an open agricultural area with a quite flat terrain. Hence, the R4 could be operated at a fixed flight height of just one metre above the surface of the terrain that is controlled actively by a radar sensor. An area of around 110 hectares were prospected within only four days. The MagDrone R4 system thus offers an outstanding survey area progress that cannot even reached by common vehicle-moved multi-sensor arrays. Here, we present the first results of this test survey by comparing the magnetograms, historical and current geodata. Most of the expected archaeological features and several unknown ones were detected by the R4 system. Our results show that the R4 system is well suited for mapping large archaeological structures with high magnetisations. In the future, we want to compare the R4 data with data from a ground-based fluxgate magnetometer. We also want to test whether the system is suitable for detecting archaeological features that have lower magnetic susceptibility and remanence contrasts with the surrounding soil.
    Description: poster
    Keywords: ddc:550 ; UAV magnetometer survey ; 3-axis fluxgate magnetometers ; archaeological prospection ; low-level flight ; Second World War airfield ; conflict landscapes
    Language: English
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    NEXD: A Software Package for Seismic Wave Simulation in Complex Geological Media – New Developments (2021)
    Details
    Publication Date: 2022-12-01
    Description: NEXD is an open source software package for the simulation of seismic waves in complex geological media. This includes elastic, viscoelastic, porous and fractured media with complex geometries. For the computation of the wave fields, the nodal discontinuous Galerkin approach (NDG) is used. The NDG approach combines unstructured tetrahedral meshes with an element-wise, high-order spatial interpolation of the wave field based on Lagrange polynomials. NEXD offers capabilities for modeling wave propagation in one-, two- and three-dimensional settings of very different spatial scale with little logistical overhead. It allows the import of external triangular (2D) and tetrahedral (3D) meshes provided by independent meshing software and can be run in a parallel computing environment. The computation of adjoint wavefields and an interface for the computation of waveform sensitivity kernels are offered. The method is verified by means of symmetry tests and the method of exact solutions. The capabilities of NEXD are demonstrated through, for example, a 2D synthetic survey of a geological carbon storage site. The most recent developments have been the inclusion of porous media in 2D and the inversion capabilities to the latest release versions of the 2D and 3D codes as well as the release of the 1D code. NEXD is available on GitHub: https://github.com/seismology-RUB.
    Description: poster
    Keywords: ddc:550 ; Numerical modelling ; Computational seismology ; Wave propagation
    Language: English
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  • 70
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    TRIPLE – Ice Data Hub, Model-based Mission Support and Forefield Reconnaissance System (2021)
    Details
    Publication Date: 2022-12-01
    Description: The ocean worlds of our Solar System, like Saturn's moon Enceladus and Jupiter's moon Europa are covered with ice. Recently, these icy moons gained further scientific interest, as they are attributed some potential to sustain or host extraterrestrial life in a subglacial ocean. The investigation of these moons will also help to understand the evolution of the Solar System. The in-situ exploration of these moons requires novel technological solutions as well as intelligent data acquisition and interpretation tools. In 2020, the DLR Space Administration started the TRIPLE project (Technologies for Rapid Ice Penetration and subglacial Lake Exploration) which develops an integrated concept for a melting probe that launches an autonomous underwater vehicle (nanoAUV) into a scientifically interesting water reservoir and an AstroBioLab for in-situ analysis. These three components build up the TRIPLE system. As part of a second project stage, it is envisioned to build the TRIPLE system and test it in Antarctica in 2026. In this contribution, we are going to present the general concept of TRIPLE with a focus on the geophysically most relevant aspects. To navigate the melting probe through the ice, a forefield reconnaissance system (TRIPLE-FRS) based on combined radar and sonar techniques is designed. This will include radar antennas directly integrated into the melting head combined with a pulse amplifier and a piezoelectric acoustic transducer just behind the melting head. In addition, an in-situ permittivity sensor will be implemented to account for the ice structure dependent propagation speed of electromagnetic waves. With this system, obstacles as well as the ice-water interface at the bottom of the icy shell could be detected. To deliver key parameters such as transit time and overall energy requirement, a virtual test bed for strategic mission planning is currently under development. This consists of the Ice Data Hub that combines available data from Earth or any other planetary body – measured or taken from the literature – and allows display, interpretation and export of data, as well as trajectory models for the melting probe. We develop high-fidelity thermal contact models for the phase change as well as macroscopic trajectory models that consider the thermodynamic melting process and the convective loss of heat via the melt-water flow.
    Description: Bundesministerium für Wirtschaft und Energie (FKZ: 50NA1908, 50RK2050, 50RK2051, 50RK2052, 50RK2053)
    Description: poster
    Keywords: ddc:550 ; Icy Moon ; mission concept ; ice melting probe ; reconnaissance
    Language: English
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  • 71
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    DFG priority programme 1788 „Dynamic Earth“: A joint interpretation of geomagnetic, geodetic and ionosphere/thermosphere data from low-orbit satellite missions (2021)
    Details
    Publication Date: 2022-12-01
    Description: Deutsche Forschungsgemeinschaft
    Description: poster
    Keywords: ddc:550
    Language: English
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  • 72
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    Simulation of Seismic Wave Propagation in Porous Rocks Considering the Exploration and the Monitoring of Geological Reservoirs (2021)
    Details
    Publication Date: 2022-12-01
    Description: Modelling the propagation of seismic waves in porous media gets more and more popular in the seismological community since it is an important but challenging task in the field of computational seismology. The fluid content of, for example, reservoir rocks or soils, and the interaction between the fluid and the rock or between different immiscible fluids has to be taken into account to accurately describe seismic wave propagation through such porous media. Often, numerical models are based on the elastic wave equation and some might include artificially introduced attenuation. This simplifies the problem but only approximates the true physics involved. Hence, the results are also simplified and could lack accuracy or miss phenomena in some applications. The aim of the conducted work was the consistent derivation of a theory for seismic wave propagation in porous media saturated by two immiscible fluids and the accompanying numerical solution for the derived wave equation. The theory is based on Biot's theory of poroelasticity. Starting from the basic conservation equations (energy, momentum, etc.) and generally accepted laws, the theory was derived using a macroscopic approach which demands that the wavelength is significantly larger than the size of the heterogeneities in the medium due to the size of the grains and pores or due to effects on the mesoscopic scale. This condition is usually fulfilled for seismic waves since the typical wavelength of seismic waves is in the order of 10 m to 10 km. Fluid flow is described by a Darcy type flow law and interactions between the fluids by means of capillary pressure curve models. In addition, consistent boundary conditions on interfaces between poroelastic media and elastic or acoustic media are derived from this poroelastic theory itself. The nodal discontinuous Galerkin method is used for the numerical modelling. The poroelastic solver is integrated into the 1D and 2D codes of the larger software package NEXD that uses the nodal discontinuous Galerkin method to solve wave equations. The implementation has been verified using symmetry tests and the method of exact solutions. This work has potential for applications in various scientific fields like, for example, exploration and monitoring of hydrocarbon or geothermal reservoirs as well as CO2 storage sites.
    Description: poster
    Keywords: ddc:550
    Language: English
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  • 73
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    Terracing and cluster analysis – new insights in potential field data prior to modelling (2022)
    Details
    Publication Date: 2022-12-01
    Description: Geological maps are complex to produce through intensive and expensive field studies. Comparisons of geophysical data with geological conditions are difficult and often only qualitatively possible. The following work therefore examines an automated procedure to better reconcile this information. For this purpose, the terracing method, and a cluster analysis of potential field (gravity and magnetic field) and petrophysical data from the Karasjok and Ligurian Sea regions are used to interpret this geophysical measurements in a geological way. Two different tectonic regions were selected: (1) The Karasjok region is located in Northern Norway, where the Karasjok Greenstone Belt (KGB) dominates geological settings, consisting of abundant ultramafic intrusions, komatiites, gabbroic intrusions, amphibolites and migmatites. (2) The Ligurian-Provençal basin, part of the Western Mediterranean Sea, which is located between the French-Italian coastline and the island of Corsica. Geologically the area is characterised by the spreading zone in the Western Mediterranean. The high-resolution Airborne Gravity Gradient Survey and aeromagnetic datasets of the Karasjok region cover an area of 20 km x 30 km with a data resolution of 50 m. The dataset of the Ligurian basin cover a much larger area with the resolution of 5 km. Data constraints come from former LOBSTER and LISA campaigns and a study in the research group at CAU Kiel, new compilation of the AlpArray Gravity Research Group (AAGRG), besides data of the ICGEM Potsdam (disturbance) and the GOCE mission. By aid of the terracing algorithm, the boundaries of the anomalies are to be sharpened and regions with constant field amplitude were generated. For this purpose, a shape index-based algorithm was applied, which uses the shape index calculated at each field point to grade the function. Through an iterative process and the variation of parameters, the terracing result is refined. The resulting data sets are then further processed using a cluster analysis method. Here, the k-mean algorithm for domain classification is used to divide the geophysical measurement data into groups (cluster) of similar properties. The number of clusters k is specified and the data points are assigned to the respective clusters through an iterative process. Using the data of the datasets mentioned above the results of this applications are successfully compared with the corresponding geological maps of the two areas.
    Description: Deutsche Forschungsgemeinschaft (DFG), SPP "MB-4D"
    Description: https://doi.org/10.5880/fidgeo.2020.045 (Zahorec et al., 2021) via GFZ Data Services
    Description: poster
    Keywords: ddc:550 ; Clustering ; terracing ; gravity field ; Liguro-Provencial Basin
    Language: English
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    Single‐Crystal Elasticity of Antigorite at High Pressures and Seismic Detection of Serpentinized Slabs (2022)
    Satta, Niccolò ; Grafulha Morales, Luiz Fernando ; Criniti, Giacomo ; [et al.]
    Details
    Publication Date: 2022-12-15
    Description: The subduction of serpentinized slabs is the dominant process to transport “water” into Earth's mantle, and plays a pivotal role for subduction dynamics. Antigorite, the most abundant serpentine mineral in subduction settings, may imprint a seismic signature on serpentinized slabs, making them seismically distinguishable from the dry, non‐serpentinized ones. However, the complete single‐crystal elasticity of antigorite has not been experimentally constrained at high pressures, hindering the use of seismological approaches to detect serpentinization in subducting slabs. Here, we report the full elastic stiffness tensor of antigorite by single‐crystal Brillouin spectroscopy and X‐ray diffraction up to 7.71(5) GPa. We use our results to model seismic properties of antigorite‐bearing rocks and show that their seismological detectability depends on the geometrical relation between seismic wave paths and foliation of serpentinized rocks. In particular, we demonstrate that seismic shear anisotropy shows low sensitivity to serpentinization for a range of relevant geometries.
    Description: Plain Language Summary: The subduction of serpentinized slabs plays a key role in the deep recycling of water into the Earth's interior. Antigorite is the main serpentine mineral in subducting slabs, and the most important carrier of water. Antigorite‐bearing rocks are predicted to have a distinct seismic signature, potentially allowing them to be detected with seismological approaches. However, our current knowledge on seismic properties of antigorite‐bearing rocks is limited, mostly hampered by a lack of experimental constraints on single‐crystal elasticity of antigorite at relevant pressures. In this study, state‐of‐the‐art techniques were employed to produce the first experimental description of the complete high‐pressure elasticity of antigorite single crystals. Our experimental data set was implemented in the modeling of seismic properties of antigorite‐bearing rocks at pressures relevant for subduction. Our results were used to discuss the relation between seismic wave path and shear wave anisotropy in serpentinized slabs, and challenge the use of shear wave splitting as a proxy for serpentinization in slabs.
    Description: Key Points: Single‐crystal elasticity of antigorite at high pressures is determined by Brillouin spectroscopy and X‐ray diffraction experiments. Seismic signature of serpentinized slabs is constrained in a relevant composition‐pressure space. Serpentinization in slabs may be undetectable through shear wave anisotropy.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: EC Horizon 2020 Framework Programme http://dx.doi.org/10.13039/100010661
    Description: https://doi.org/10.6084/m9.figshare.20348748
    Description: https://doi.org/10.6084/m9.figshare.20348781
    Keywords: ddc:550 ; serpentine ; elasticity ; Brillouin spectroscopy ; antigorite ; seismic anisotropy ; shear wave splitting
    Language: English
    Type: doc-type:article
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