ALBERT

Description: Deep hydrothermal Mo, W and base metal mineralization found in the Detroit City portal of the Sweet Home mine in the Alma district (Colorado Mineral Belt) was deposited in response to magmatic activity and the formation of Climax-type Mo deposits during the Oligocene. This study presents extensive geochemical analyses of fluid inclusions inminerals from early greisen-like vein mineralization to better understand the fluid system responsible for ore formation. Quartz and fluorite, which are associated with molybdenite, huebnerite and/or pyrite mineralization, precipitated from low- to medium-salinity (1.5-11.5 wt.% equiv. NaCl), CO2-bearing fluids at temperatures between 360 and 415°C and probably under a fluctuating pressure regime at depths of at least 3.5 km. The formation of greisen-like and base metal mineralization at the Detroit City portal of the Sweet Home mine is related to fluids of different origin. Early magmatic fluids were the principal source for mantle-derived volatiles (CO2, H2S/SO2, noble gases) and mixed with significant amounts of heated meteoric water. Fluid mixing of magmatic fluids with meteoric water is constrained by δ 2H-δ 18O relationships of fluid inclusion water in different minerals (Fig. 1). Whether molybdenum was derived from magmatic fluids remains unclear. Fluid inclusions in huebnerite suggest that W originated from source rocks that are enriched in organic matter rather than from magmatic fluids. The deep hydrothermal mineralization at the Detroit City portal of the Sweet Home mine shows features similar to deep hydrothermal vein mineralization found in Climax-type Mo deposits and their periphery, suggesting that fluid migration and the deposition of ore and gangue minerals in the Sweet Home mine was triggered by a deep-seated magmatic intrusion. The findings of this study are in good agreement with the results of previous fluid inclusion studies of the mineralization of the Sweet Home mine (Lüders et al., 2009) and from Climaxtype Mo porphyry deposits in the Colorado Mineral Belt (Hall et al., 1974).

Description: By means of 4 years of Challenging Minisatellite Payload (CHAMP) zonal wind observations and a Thermosphere-Ionosphere Electrodynamics General Circulation Model simulation, longitudinal and seasonal variations of thermospheric superrotation at magnetic equator are investigated first. The superrotation shows four- and three-peaked longitudinal patterns in March and September equinoxes, and a two-peaked variation during solstices. The superrotation is stronger in December than in June solstice, and stronger in March than in September equinox. The mean correlation between the zonal variation of superrotation and nighttime eastward wind is about 0.8, while it is 0.6 with daytime westward zonal wind. The interaction between the neutral wind and geomagnetic field plays a more important role in the superrotation, rather than the F-region electron density. The lower atmospheric tides tend to suppress the superrotation, but contribute to the longitudinal patterns of the superrotation. The viscous force is also important for the longitudinal modulation of the superrotation.

Description: We report the concurrent observations of F-region plasma changes and field-aligned currents (FACs) above isolated proton auroras (IPAs) associated with electromagnetic ion cyclotron Pc1 waves. Key events on March 19, 2020 and September 12, 2018 show that ground magnetometers and all-sky imagers detected concurrent Pc1 wave and IPA, during which NOAA POES observed precipitating energetic protons. In the ionospheric F-layer above the IPA zone, the Swarm satellites observed transverse Pc1 waves, which span wider latitudes than IPA. Around IPA, Swarm also detected the bipolar FAC and localized plasma density enhancement, which is occasionally surrounded by wide/shallow depletion. This indicates that wave-induced proton precipitation contributes to the energy transfer from the magnetosphere to the ionosphere.

Description: Tropical forests store 40–50 per cent of terrestrial vegetation carbon1. However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests2. Owing to climatic and soil changes with increasing elevation3, AGC stocks are lower in tropical montane forests compared with lowland forests2. Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1–164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network4 and about 70 per cent and 32 per cent higher than averages from plot networks in montane2,5,6 and lowland7 forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa8. We find that the low stem density and high abundance of large trees of African lowland forests4 is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse9,10 and carbon-rich ecosystems.

Description: The Huanghe once had a sediment flux of 〉1,000 Mt/yr, but this has decreased by ∼90% as its river sediment routing systems have undergone dramatic changes influenced by human activities such as dam construction. However, the way in which the sediment geochemistry of the river has responded to the altered sediment routing processes is not well known. This study investigates the sediment source-to-sink routing regime of the Huanghe River using Nd isotope fingerprinting. Four major source terranes, namely the Songpan-Ganzi (SG) Block, Ordos Desert (OD), Chinese Loess Plateau (CLP) and North China Craton (NCC) are recognized according to their distinct Nd isotopes. The gradual downstream decrease in εNd values in sediments of the upper Huanghe indicates a decreasing contribution of material from the SG Block and a corresponding increase contribution of local underlying basement rocks, which is inferred to be related to sediment capture by a cascade of hydroelectric dams. A gradual increase in εNd from Yinchuan to Tongguan suggests an increasing contribution from the CLP under intense erosion. Relatively low εNd in the downstream sediments suggest a contribution from proximal NCC basement, consistent with the shift from deposition to erosion in the lower channel in recent years. The marked heterogeneity in Nd isotopes in the Huanghe sediments corresponds well to sediment source-to-sink processes in response to increasing human impacts. In a setting of global rivers facing strong anthropogenic impacts, the ways in which altered sediment routing systems affect river sediment geochemistry deserve more research attention.

Description: In this study, the effect of disturbance dynamo electric field (DDEF) induced by subauroral polarization streams (SAPS) on the variations of the equatorial electrojet (EEJ) and its counter electrojet (CEJ) during the geomagnetic storm on June 1, 2013 is analyzed in detail for the first time. Observations from ground-based magnetometers showed that the SAPS-induced EEJ flows westward and eastward in the daytime and dawn/dusk sectors, respectively. The effects of SAPS on EEJ are mainly associated with the changes of zonal ionospheric electric field, while the changes in the ionospheric conductivity play a secondary role. By using Thermosphere Ionosphere Electrodynamic General Circulation Model simulations, the zonal electric field induced by SAPS associated with the DDEF is examined. The results of the simulations show that the DDEF has a significant impact on the EEJ variability. The daytime westward EEJ at the dip equator is mainly driven by disturbance zonal wind, with secondary contributions from disturbance meridional wind. A similar mechanism can be observed in the dawn/dusk sector when the eastward EEJ is produced; however, it has a much weaker intensity than that during the daytime.

Description: CO2 release from particulate organic carbon (POC) oxidation during fluvial transit can influence climate over a range of timescales. Identifying the mechanistic controls on such carbon fluxes requires determining where POC oxidation occurs in river systems. While field data show POC oxidation and replacement moving downstream in lowland rivers, flume studies show that oxidation during active fluvial transport is limited. This suggests that most fluvial POC oxidation occurs during transient floodplain storage, but this idea has yet to be tested. Here, we isolate the influence of floodplain storage time on POC oxidation by exploiting a chronosequence of floodplain deposits above the modern groundwater table in the Rio Bermejo, Argentina. Measurements from 15 floodplain cores with depositional ages from 1 y to 20 ky show a progressive POC concentration decrease and 13C-enrichment with increasing time spent in floodplain storage. These results from the Rio Bermejo indicate that over 80% of fluvially-deposited POC can be oxidized over millennial timescales in aerated floodplains. Furthermore, POC in the oldest floodplain cores is more 14C-enriched than expected based on the independently-dated floodplain ages, indicating that a portion of this oxidized POC is replaced by autochthonous POC produced primarily by floodplain vegetation. We suggest floodplain storage timescales control the extent of oxidation of fluvially-deposited POC, and may play a prominent role in determining if rivers are significant atmospheric CO2 sources.

Description: Geochemical processes such as mineral dissolution and precipitation alter the microstructure of rocks, and thereby affect their hydraulic and mechanical behaviour. Quantifying these property changes and considering them in reservoir simulations is essential for a sustainable utilisation of the geological subsurface. Due to the lack of alternatives, analytical methods and empirical relations are currently applied to estimate evolving hydraulic and mechanical rock properties associated with chemical reactions. However, the predictive capabilities of analytical approaches remain limited, since they assume idealised microstructures, and thus are not able to reflect property evolution for dynamic processes. Hence, aim of the present thesis is to improve the prediction of permeability and stiffness changes resulting from pore space alterations of reservoir sandstones. A detailed representation of rock microstructure, including the morphology and connectivity of pores, is essential to accurately determine physical rock properties. For that purpose, three-dimensional pore-scale models of typical reservoir sandstones, obtained from highly resolved micro-computed tomography (micro-CT), are used to numerically calculate permeability and stiffness. In order to adequately depict characteristic distributions of secondary minerals, the virtual samples are systematically altered and resulting trends among the geometric, hydraulic, and mechanical rock properties are quantified. It is demonstrated that the geochemical reaction regime controls the location of mineral precipitation within the pore space, and thereby crucially affects the permeability evolution. This emphasises the requirement of determining distinctive porosity-permeability relationships by means of digital pore-scale models. By contrast, a substantial impact of spatial alterations patterns on the stiffness evolution of reservoir sandstones are only observed in case of certain microstructures, such as highly porous granular rocks or sandstones comprising framework-supporting cementations. In order to construct synthetic granular samples a process-based approach is proposed including grain deposition and diagenetic cementation. It is demonstrated that the generated samples reliably represent the microstructural complexity of natural sandstones. Thereby, general limitations of imaging techniques can be overcome and various realisations of granular rocks can be flexibly produced. These can be further altered by virtual experiments, offering a fast and cost-effective way to examine the impact of precipitation, dissolution or fracturing on various petrophysical correlations. The presented research work provides methodological principles to quantify trends in permeability and stiffness resulting from geochemical processes. The calculated physical property relations are directly linked to pore-scale alterations, and thus have a higher accuracy than commonly applied analytical approaches. This will considerably improve the predictive capabilities of reservoir models, and is further relevant to assess and reduce potential risks, such as productivity or injectivity losses as well as reservoir compaction or fault reactivation. Hence, the proposed method is of paramount importance for a wide range of natural and engineered subsurface applications, including geothermal energy systems, hydrocarbon reservoirs, CO2 and energy storage as well as hydrothermal deposit exploration

Description: Geochemische Lösungs- und Fällungsprozesse verändern die Struktur des Porenraums und können dadurch die hydraulischen und mechanischen Gesteinseigenschaften erheblich beeinflussen. Die Quantifizierung dieser Parameteränderung und ihre Berücksichtigung in Reservoirmodellen ist entscheidend für eine nachhaltige Nutzung des geologischen Untergrunds. Aufgrund fehlender Alternativen werden dafür bisher analytische Methoden genutzt. Da diese Ansätze eine idealisierte Mikrostruktur annehmen, können insbesondere Änderungen der Gesteinseigenschaften infolge von dynamischen Prozessen nicht zuverlässig abgebildet werden. Ziel der vorliegenden Doktorarbeit ist es deshalb, die Entwicklung von Gesteinspermeabilitäten und -steifigkeiten aufgrund von Porenraumveränderungen genauer vorherzusagen. Für die möglichst exakte Bestimmung physikalischer Gesteinsparameter ist eine detaillierte Darstellung der Mikrostruktur notwendig. Basierend auf mikro-computertomographischen Scans werden daher hochaufgelöste, dreidimensionale Modelle typischer Reservoirsandsteine erstellt und Gesteinspermeabilität und -steifigkeit numerisch berechnet. Um charakteristische Verteilungen von Sekundärmineralen abzubilden, wird der Porenraum dieser virtuellen Sandsteinproben systematisch verändert und die resultierenden Auswirkungen auf die granulometrischen, hydraulischen und elastischen Gesteinseigenschaften bestimmt. Die Ergebnisse zeigen deutlich, dass charakteristische Fällungsmuster unterschiedlicher geochemischer Reaktionsregime die Permeabilität erheblich beeinflussen. Folglich ist die Nutzung von porenskaligen Modellen zur Bestimmung der Porosität-Permeabilitätsbeziehungen unbedingt notwendig. Im Gegensatz dazu ist die Verteilung von Sekundärmineralen für die Gesteinssteifigkeit nur bei bestimmten Mikrostrukturen von Bedeutung, hierzu zählen hochporöse Sandsteine oder solche mit Korngerüst-stützenden Zementierungen. In der Arbeit wird außerdem ein Ansatz zur Konstruktion granularer Gesteine vorgestellt, welcher sowohl die Kornsedimentation als auch die diagenetische Verfestigung umfasst. Es wird gezeigt, dass die synthetischen Proben die mikrostrukturelle Komplexität natürlicher Reservoirsandsteine gut abbilden. Dadurch können generelle Limitationen von bildgebenden Verfahren überwunden und unterschiedlichste virtuelle Repräsentationen von granularen Gesteinen generiert werden. Die synthetischen Proben können zukünftig in virtuellen Experimenten verwendet werden, um die Auswirkungen von Lösungs- und Fällungsreaktionen auf verschiedene petrophysikalische Korrelationen zu untersuchen. Die vorgestellte Arbeit liefert methodische Grundlagen zur Quantifizierung von Permeabilitäts- und Steifigkeitsänderungen infolge geochemischer Prozesse. Die berechneten petrophysikalischen Beziehungen basieren direkt auf mikrostrukturellen Veränderungen des Porenraums. Daher bieten sie eine genauere Vorhersage der Gesteinseigenschaften als herkömmliche analytische Methoden, wodurch sich die Aussagekraft von Reservoirmodellen erheblich verbessert. Somit können Risiken, wie Produktivitäts- oder Injektivitätsverluste sowie Reservoirkompaktion oder Störungsreaktivierung, verringert werden. Die präsentierten Ergebnisse sind daher relevant für verschiedenste Bereiche der geologischen Untergrundnutzung wie CO2- oder Energiespeicherung, Geothermie, Kohlenwasserstoffgewinnung sowie die Erkundung hydrothermaler Lagerstätten.

Description: Monitoring and controlling of mineral precipitation is a major challenge in several industry segments such as oil and gas or geothermal energy. Especially at elevated pressures, temperatures, and salinities, these reactions are poorly understood and difficult to predict. Real-time monitoring under such conditions, however, is crucial for reduction or prevention of scaling as well as for process modelling. In this study, a novel fibre-optical method for monitoring the barite precipitation process at high pressures and high temperatures was developed and tested. The applicability of a fibre-optical sensor was demonstrated and kinetic data derived from experiments using synthetic fluids that were oversaturated with barite. The ionic strength was varied between 0 and 5 mol/l NaCl to simulate geothermal brines typically found in deep sedimentary reservoirs. Experiments were performed at 25 and 150 °C. For the studied variations it was found that the ionic strength had a strong impact on the barite precipitation rate whereas temperature had only a minor influence. The kinetic rate constants were decreasing with increasing salinity ranging from 9 to 0.4 l‧mol−1‧s−1 at 25 °C and from 8.6 to 0.66 l‧mol−1‧s−1 at 150 °C.

Description: New data acquisition techniques are generating data at much finer temporal and spatial resolution, compared to traditional seismic experiments. This is a challenge for data centers and users. As the amount of data potentially flowing into data centers increases by one or two orders of magnitude, data management challenges are found throughout all stages of the data flow. The Incorporated Research Institutions for Seismology—Réseau sismologique et géodésique français and GEOForschungsNetz data centers—carried out a survey and conducted interviews of users working with very large datasets to understand their needs and expectations. One of the conclusions is that existing data formats and services are not well suited for users of large datasets. Data centers are exploring storage solutions, data formats, and data delivery options to meet large dataset user needs. New approaches will need to be discussed within the community, to establish large dataset standards and best practices, perhaps through participation of stakeholders and users in discussion groups and forums.

Description: Earth’s lowermost mantle displays complex geological phenomena that likely result from its heterogeneous physical interaction with the core. Geophysical models of core-mantle interaction rely on the thermal and electrical conductivities of appropriate geomaterials which, however, have never been probed at representative pressure and temperature (P-T) conditions. Here we report on the opacity of single crystalline bridgmanite and ferropericlase and link it to their radiative and electrical conductivities. Our results show that light absorption in the visible spectral range is enhanced upon heating in both minerals but the rate of change in opacity with temperature is a factor of six higher in ferropericlase. As a result, bridgmanite in the lowermost mantle is moderately transparent while ferropericlase is highly opaque. Our measurements support previous indirect estimates of low (〈 1 W/m/K) and largely temperature-independent radiative conductivity in the lowermost mantle. This implies that the radiative mechanism has not contributed significantly to cooling the Earth’s core throughout the geologic time. Opaque ferropericlase is electrically conducting and mediates strong core-mantle electromagnetic coupling, explaining the intradecadal oscillations in the length of day, low secular geomagnetic variations in Central Pacific, and the preferred paths of geomagnetic pole reversals.

Description: The SWATH‐D experiment involved the deployment of a dense temporary broadband seismic network in the Eastern Alps. Its primary purpose was enhanced seismic imaging of the crust and crust–mantle transition, as well as improved constraints on local event locations and focal mechanisms in a complex part of the Alpine orogen. The study region is a key area of the Alps, where European crust in the north is juxtaposed and partially interwoven with Adriatic crust in the south, and a significant jump in the Moho depth was observed by the 2002 TRANSALP north–south profile. Here, a flip in subduction polarity has been suggested to occur. This dense network encompasses 163 stations and complements the larger‐scale sparser AlpArray seismic network. The nominal station spacing in SWATH‐D is 15 km in a high alpine, yet densely populated and industrialized region. We present here the challenges resulting from operating a large broadband network under these conditions and summarize how we addressed them, including the way we planned, deployed, maintained, and operated the stations in the field. Finally, we present some recommendations based on our experiences.

Description: Potassium feldspars (KAlSi3O8) are ubiquitous minerals in the Earth's upper crust. This family of minerals has been the subject of numerous experimental and theoretical investigations concerning their dissolution kinetics and the mechanisms controlling chemical alteration at acid and neutral pH, and at temperatures ranging from ambient to hydrothermal conditions. On the other hand, considerably less research on the dissolution behavior of K-feldspars has been carried out at alkaline conditions, in particular at pH 〉 9 and elevated temperatures. Filling in this gap in knowledge is the major motivation for this study. More specifically, we wanted to document and understand how the K-feldspar interface structurally and chemically evolves during alteration in order to determine the mechanism of dissolution. In this study we examined interfaces of orthoclase samples that were altered in separate experiments in a Ca(OH)2-H2O solution (pH25°C 12.4) at 190 °C for 24 h. We used a combination of focused ion beam (FIB) milling and advanced analytical transmission electron microscopy (TEM) techniques to investigate the structure and chemistry of the near surface region of post-reaction grains, with particular attention being given to the fluid-solid interface. Even though each grain diminishes in volume due to dissolution, high-resolution TEM imaging indicates that the feldspar structure itself remains completely intact and crystalline, as evidenced by lattice fringes that abruptly terminate at the grain edge. Nanometer-scale chemical composition measurements and mapping by TEM-EDXS (energy dispersive X-ray spectroscopy) and EFTEM (energy filtered TEM) show that the chemistry of the parent feldspar also remains unchanged at the interface. In particular, there is no evidence for the incursion of Ca from the fluid solvent into the structure, either by interdiffusion or by a replacement process. Taken together, the TEM observations point to a sharp chemical reaction front characterized by the congruent (i.e. stoichiometric) release of all elements from the feldspar structure. Nanometer-scale measurements by high resolution analytical TEM also reveal that a surface alteration layer (SAL) of amorphous material forms in situ at the expense of the feldspar structure. The interface demarcates a spatially coincident and nm-sharp chemical and structural discontinuity between the parent feldspar and the amorphous phase. The amorphous SAL has a variable thickness, from under 10 nm up to ~200 nm. This is likely one of the first observed occurrences of a significant surface amorphous layer on feldspar due to alteration in an alkaline solvent. The lack of a gap between the two phases points to an interfacial dissolution-reprecipitation process that continuously operates during hydrothermal alteration, and mostly likely right from the onset of contact with the fluid. After the initial formation of the amorphous layer, a 1–2 μm-thick porous amalgam of secondary crystalline phases comprised of calcite, tobermorite, and hydrogrossular, as well as other minor phases, precipitated over the SAL. These authigenic crystalline minerals formed during the experiment (hydrothermal alteration, followed by fluid loss due to evaporation) by a classical thermodynamically-controlled precipitation process as the reactor bulk fluid became increasingly concentrated. We propose that a coupled interfacial dissolution-reprecipitation (CIDR) mechanism best explains the chemical and structural properties of the interface and the formation of an amorphous surface layer. In fact, many recent studies postulate that a CIDR process controls feldspar dissolution and the formation of SALs at acid and circumneutral pH over a wide range of temperatures. Combining these previous results with our new observations supports the idea that a unique and unifying mechanism likely controls chemical alteration of feldspars in all aqueous fluids.

Description: Precise point positioning with ambiguity resolution (PPP-AR) is a powerful tool for geodetic and time-constrained applications that require high precision. The performance of PPP-AR highly depends on the reliability of the correct integer carrier-phase ambiguity estimation. In this study, the performance of narrow-lane ambiguity resolution of PPP using the Least-squares AMBiguity Decorrelation (LAMBDA) and bootstrapping methods is extensively investigated using real data from 55 IGS stations over one-month in 2020. Static PPP with 24-, 12-, 8-, 4-, 2-, 1- and ½-h sessions using two different cutoff angles (7° and 30°) was conducted with three PPP modes: i.e. ambiguity-float and two kinds of ambiguity-fixed PPP using the LAMBDA and bootstrapping methods for narrow-lane AR, respectively. The results show that the LAMBDA method can produce more reliable results for 2 hour and shorter observation sessions compared with the bootstrapping method using a 7° cutoff angle. For a 30° cutoff angle, the LAMBDA method outperforms the bootstrapping method for observation sessions of 4 h and less. For long observation times, the bootstrapping method produced much more accurate coordinates compared with the LAMBDA method without considering the wrong fixes cases. The results also show that occurrences of fixing the wrong integer ambiguities using the bootstrapping method are higher than that of the LAMBDA method.

Description: The project DARE proposes an integrated study of seismic site effects on the deep and elongated Messinian Rhône Canyon (French Rhône Valley). Lithological information from boreholes reaching the bedrock and preliminary geophysical campaigns indicate that the canyon can reach locally 〉500 m and may be deeply incised. The strong material contrast between the sedimentary filling and the substratum, as well as its expected confined geometry make this canyon a good candidate for generating various kinds of multi-dimensional site effects. Waveform data are available from the GEOFON data centre, under network code Y7.

Description: The temporary seismic array of MySCOLAR in northern Myanmar consists of 30 broadband stations. The overall scientific goals are to understand the transition from continental collision to oceanic subduction, to quantify the partitioning of deformation in the accretionary prism, in the Burma Plate and along the strike-slip Sagaing fault system and to image the subducting Indian Plate beneath Myanmar and southwest China. The seismological analysis methods applied to this dataset will include location of local earthquakes and determining their focal mechanisms, surface wave tomography from ambient noise and earthquake data, body wave tomography from local and teleseismic earthquakes, full waveform inversion for Earth structure, receiver functions, and shear wave splitting. A subset of the stations was transmitting data in real time, and these stations contributed to real-time earthquake analysis by the Department of Meteorology and Hydrology (DMH) in Myanmar and the GEOFON earthquake monitoring service. Waveform data are available from the GEOFON data centre, under network code 6C.

Description: The Villarrica Volcano is one of the most active volcanoes in South America and is located in a major tourism region. A dense seismological network is used to investigate the seismic characteristics of the volcano and its seismic structure tomographically with high spatial resolution. The network was in operation for 2 week from 01.03.2012 to 14.03.2012. It consisted of 30 3-component and 45 1-component short period seismographs covering an area of 2000 km*2. The covered area has a diameter of 45 km and includes the volcanic building.

Description: The main aim of this project is to investigate the crustal and mantle structure beneath the Longmenshan fault zone in China, based on a very dense passive seismology profile. The Longmenshan fault zone hosted the Wenchuan earthquake of May 2008 with a magnitude (Mw) of 7.9 and the Lushan earthquake of June 2013 with a magnitude (Mw) of 6.6. It is planned to mainly use the receiver-function method, to investigate the crustal and mantle structure beneath the Longmenshan fault zone. Waveform data are available from the GEOFON data center, under network code 4O under license CC BY-NC-ND 4.0, and are embargoed until February 2024.

Description: Irpinia seismic Array is part of the DEnse mulTi-paramEtriC observations and 4D high resoluTion imaging (DETECT) project focused on the acquisition of a unique multiparametric dataset and fosters collaboration among various institutions. The University of Naples Federico II (UniNa) and the German Research Centre for Geosciences (GFZ) are leading this effort carried out in collaboration with various local institutions and supported by the local municipalities. The DETECT project aims at exploiting very dense seismic networks deployed across a segmented fault system (Irpinia and Pergola-Melandro) to foster the development of scientific integrated methodologies for monitoring and imaging the fault behavior during the inter-seismic phase. The Irpinia seismic Array consists of a dense constellation of seismic antennas using more than 200 seismic stations deployed for one year. Each seismic antenna, with maximum aperture of ~2 km, uses one broad-band sensor, one short period sensor with 1 Hz and 8 with 4.5 Hz natural frequency. The antennas are deployed above and near the fault segments that generated during the last centuries many strong earthquakes in the southern Apennines. Waveform data are available from the GEOFON data centre, under network code ZK.

Description: The Villarrica Volcano is one of the most active volcanoes in South America and is located in a major tourism region. A dense temporal seismological network was installed to investigate the volcanic seismicity and the seismic structure of the edifice with seismic traveltime tomography at high spatial resolution. The network was in operation for 2 weeks from 01.03.2012 to 14.03.2012. It consisted of 30 three-component and 45 one-component short period seismographs covering an area of about 2000 km2. The covered area has a diameter of 45 km and includes the volcanic building.

Description: Study Region Vietnamese Mekong Delta. Study focus This study investigates the trends of groundwater levels (GWLs), the memory effect of alluvial aquifers, and the response times between surface water and groundwater across the Vietnamese Mekong Delta (VMD). Trend analysis, auto- and cross-correlation, and time-series decomposition were applied within a moving window approach to examine non-stationary behavior. New hydrological insights Our study revealed an effective connection between the shallowest aquifer unit (Holocene) and surface water, and a high potential for shallow groundwater recharge. However, low-permeable aquicludes separating the aquifers behave as low-pass filters that reduce the high‐frequency signals in the GWL variations, and limit the recharge to the deep groundwater. Declining GWLs (0.01−0.55 m/year) were detected for all aquifers throughout the 22 years of observation, indicating that the groundwater abstraction exceeds groundwater recharge. Stronger declining trends were detected for deeper groundwater. The dynamic trend analysis indicates that the decrease of GWLs accelerated continuously. The groundwater memory effect varied according to the geographical location, being shorter in shallow aquifers and flood-prone areas and longer in deep aquifers and coastal areas. Variation of the response time between the river and alluvial aquifers was controlled by groundwater depth and season. The response time was shorter during the flood season, indicating that the bulk of groundwater recharge occurred in the late flood season, particularly in the deep aquifers.

Description: Important aspects of geothermal exploration and exploitation are the assessment and mitigation of natural and/or induced seismicity, the imaging and resource assessment of a geothermal reservoir and the monitoring of the effects of the exploitation activities. With this thesis the analysis and application of various seismological tools for the planning, exploration, and monitoring of geothermal fields are given. The methods explored and further developed include survey design for microseismic network construction and assessment, local earthquake tomography, ambient noise tomography, and coda wave interferometry. These techniques were applied to study Los Humeros (Mexico), Theistareykir (Iceland) and Reykjanes (Iceland) geothermal fields. The geometry of seismological arrays is essential for high quality seismic event retrieval and minimal location errors. A sequential survey design algorithm that uses a quality measure based on the D-criterion was applied to extend the seismic network at Theistareykir and to qualify the geometry of the Reykjanes network. Assuming mean picking errors of tp =0.2 s and ts = 0.4 s, the extended Theistareykir network presented an improvement of ∼0.2 km for the computed hypocentral components of seismic events located within the new network. Conversely, we estimated that the Reykjanes network could spare up to 18 of its station locations and obtain comparable location errors nonetheless. This study showed thei mportance of prior survey design experiments to optimize the expenses for a geothermal project (required number of sensors) while obtaining good location estimates of expected seismic events (benefit/cost relations). To characterize the seismic structures at Los Humeros and Theistareykir geothermal fields, a local earthquake tomography and an ambient noise tomography were computed at both locations, respectively. A local earthquake tomography is feasible in areas with high seismicity and good ray coverage (earthquake/station geometries). On the other hand, an ambient noise tomography depends on a good and sufficiently dense station distribution. With the results of these studies, the seismic structures and the dynamics of these two producing fields were obtained for the first time. The seismicity distribution at Los Humeros was used to characterize structures and potential permeability enhancements in some of the existing faults. The retrieved Vp model was combined with available well log data and ultrasonic pulse measurements of collected rock samples to estimate the boundaries of different geologic units. The Vp/Vs model was then used in combination with resistivity data and surface CO2 measurements to deduce the geometry of the conductive clay cap (Vp/Vs ≤ 1.65 and resistivities ≤ 10 Ωm), to identify fluid (Vp reduction, Vp/Vs ≥ 1.71, and resistivities between ∼ 10-60 Ωm), and to locate gas bearing regions (Vp/Vs ≤ 1.55 and high surface CO2 concentrations). A similar study was carried out at Theistareykir, where the Vs model was combined with resistivity data to identify magmatic and/or hydrothermal bodies (Vs ≤ -7 %, resistivities ≤ 30 Ωm). An important conclusion from these studies is that the combination of seismic properties with additional geological and/or geophysical data avoids ambiguities and provides robust interpretations of the dynamics and structure of a geothermal reservoir. Finally, a coda wave interferometry technique (stretching method) was applied to two years of ambient noise records at the Theistareykir geothermal field with the aim to monitor possible velocity changes due to the exploitation activities. Here, the effects of the injection and production changes were very small on the computed Δv/v ratio and only a small long-term velocity reduction (possibly due to production) was detected (-0.05 %/year at the producing field compared to a regional -0.04 %/year). Such observations are also very relevant for the safe long-term continuation of exploitation activities. Although not yet a standard practice, the computation of these changes is very useful to control aseismic processes prior to potentially triggered/induced large seismic events and is complementary to microseismic monitoring. With these results, this thesis contributes to the efforts of the International Energy Agency to develop and increase the use of geothermal energy.

Description: Wichtige Aspekte der geothermischen Exploration und Nutzung sind die Bewertung und Reduzierung der natürlichen und/oder induzierten Seismizität, die Abbildung und Ressourcenbewertung eines geothermischen Reservoirs, sowie die Überwachung der Auswirkungen der Explorationsaktivitäten. In dieser Arbeit werden die Analysen und Anwendungen verschiedener seismologischer Methoden zur Planung, Erkundung und Überwachung geothermischer Felder vorgestellt. Die untersuchten und hier weiterentwickelten Methoden umfassen das Design für den Aufbau und die Bewertung mikroseismischer Netzwerke, die lokale Erdbebentomographie, die Ambient-Noise-Tomographie und die Coda-Wellen-Interferometrie. Diese Techniken werden angewendet, um die geothermischen Felder Los Humeros (Mexiko), Theistareykir (Island) und Reykjanes (Island) zu untersuchen. Die Geometrie seismologischer Arrays ist essentiell für eine gute Bestimmung seismischer Ereignisse mit kleinen Lokationsungenauigkeiten. Ein sequenzieller Algorithmus zum Design des Arrays, der eine Qualitätskennzahl auf der Grundlage des D-Kriteriums verwendet, wurde benutzt, um das seismische Netzwerk in Theistareykir zu erweitern und die Geometrie des Reykjanes-Netzwerks zu testen. Unter der Annahme von mittleren Ablesefehlern von tp = 0.2 s und ts = 0.4 s für P- und S- Wellen verbessert das erweiterte Theistareykir-Netzwerk die berechneten Hypo-Zentren um 0.2 km innerhalb des neuen Netzes. Das Reykjanes-Netz könnte andererseits um bis zu 18 Stationsstandorte reduziert werden und dennoch vergleichbare Lokationsgenauigkeiten erzielen. Diese Studie zeigte die Wichtigkeit vor den eigentlichen Feld-Experimenten Tests möglicher Array-Designs durchzuführen um die Kosten für ein geothermisches Projekt (erforderliche Anzahl von Sensoren) zu optimieren und gleichzeitig gute Lokationen für erwartete seismische Ereignisse zu erhalten (Nutzen/Kostenverhältniss). Um die seismischen Strukturen der geothermischen Felder Los Humeros und Theistareykir zu charakterisieren, wurden an beiden Standorten eine lokale Erdbebentomographie und eine Ambient-Noise-Tomographie berechnet. Eine lokale Erdbebentomographie ist in Gebieten mit hoher Seismizität und guter Strahlenabdeckung (Erdbeben/Stationsgeometrie) möglich. Eine Ambient-Noise-Tomographie hängt nur von einer guten und ausreichend dichten Stationsverteilung ab. Mit den Ergebnissen dieser Studien wurden dann erstmals die seismischen Strukturen und die Dynamik dieser beiden produzierenden Felder ermittelt. Die Seismizitätsverteilung in Los Humeros wurde verwendet, um Strukturen und potenzielle Verbesserungen in der Durchlässigkeit einiger Störungszonen zu charakterisieren. Das abgeleitete Vp-Modell wurde mit Bohrloch-Daten und Ultraschall-Messungen an Gesteinsproben kombiniert, um die Grenzen verschiedener geologischer Einheiten abzuschätzen. Das Vp/Vs-Modell wurde dann in Kombination mit Widerstandsdaten und Oberflächen-CO2-Messungen verwendet, um die Geometrie der leitfähigen Tonkappe abzuleiten (Vp/Vs ≤ 1.65 und Widerstand ≤ 10 Ωm), um Fluide zu identifizieren (reduzierte Vp Werte, Vp/Vs ≥ 1.71 und Widerstände zwischen 10-60 Ωm) und um gasführende Bereiche zu lokalisieren (Vp/Vs ≤ 1.55 und hohe CO2-Konzentrationen). Eine ähnliche Studie wurde in Theistareykir durchgeführt, wo das Vs-Modell mit Widerstandsdaten kombiniert wurde, um magmatische und/oder hydrothermale Körper zu identifizieren (Vs ≤ -7 %, Widerstände ≤ 30 Ωm). Eine wichtige Schlussfolgerung aus diesen Studien ist, dass die Kombination von seismischen Eigenschaften mit zusätzlichen geologischen und/oder geophysikalischen Daten Mehrdeutigkeiten vermeidet und robuste Interpretationen der Dynamik und Struktur eines geothermischen Reservoirs liefert. Weiterhin wurde eine Coda-Wellen-Interferometrie-Technik (Dehnungsmethode) auf zwei Jahre Ambient-Noise-Daten im Geothermiefeld Theistareykir angewendet, um mögliche Geschwindigkeitsänderungen aufgrund der Nutzung des Feldes zu überwachen. Hier waren die Auswirkungen der Injektions- und Produktionsveränderungen auf das Δv/v-Verhältnis sehr gering und nur eine kleine, möglicherweise produktionsbedingte, langfristige Geschwindigkeitsreduktion wurde festgestellt (-0.05 %/Jahr innerhalb des Produktionsbereichs im Vergleich zum regionalen Wert von -0.04 %/Jahr). Solche Beobachtungen sind für die sichere langfristige Ausbeutung von geothermischen Feldern von großer Bedeutung. Obwohl es noch keine Standardpraxis ist, ist die Berechnung dieser Änderungen weiterhin sehr nützlich, um aseismische Prozesse vor potenziell ausgelösten/induzierten großen seismischen Ereignissen zu steuern, sie ergänzen weiterhin die mikroseismische Überwachung. Mit diesen Ergebnissen trägt die vorgelegte Arbeit zu den Bemühungen der Internationalen Energieagentur bei, die Nutzung von Geothermie zu entwickeln und zu erhöhen.

Description: The Caribbean and South American tectonic plates bound the north-eastwards expulsion of the North Andean Block in western Venezuela. This complicated geodynamic setting resulted in the formation of major strike-slip fault systems and sizeable mountain chains. The 100 km wide Mérida Andes extend from the Colombian/Venezuelan border to the Coastal Cordillera. To the north and south, the Mérida Andes are bound by hydrocarbon-rich sedimentary basins. Knowledge of lithospheric structures, related to the formation of the Mérida Andes, is limited though, due to a lack of deep geophysical data. This thesis presents the results of the first broadband magnetotelluric profile crossing the Mérida Andes and the Maracaibo and Barinas-Apure foreland basins spanning a distance of 240 km. The MT dataset consists of 72 stations installed during March and April 2015 with a minimum recording period of 3 days per station. Geoelectrical strike and dimensionality analyses are consistent with one- or two- dimensional subsurface structures for the sedimentary basins yet also indicate a strong three- dimensional setting for the Mérida Andes. Even more significantly, these analyses showed the presence of off-profile features that influenced the data considerably, particularly at long periods. Therefore, a combination of 2D and 3D modelling was necessary for analysing the geoelectrical structures associated with this dataset. Off-profile structures can significantly affect the outcome of a 2D inversion. Thus, the systematic examination of the influence of 3D structures on 2D inversions was necessary to support the obtained result. Synthetic data sets derived from 3D modelling allowed identification and quantification of spurious off-profile features as well as smoothing artefacts due to limited areal station coverage of data collected along a profile. In general, structures in the 2D inversion are affected by the projection and rotation of the data resulting in sub-horizontal anomalies to reproduce the oblique extent of the fault systems and sedimentary basins. Moreover, a profile distributed dataset can limit the lateral resolution of a 3D inversion considerably. Hence, the effect of data distribution on a 3D inversion was carefully studied to determine the areas of the models that can be confidently explained by the data. To this end, several synthetic datasets were derived from 3D models with varying levels of complexity. The analysis of the synthetic datasets allows determination of the lateral resolution of the 3D models and identification of spurious shallow and deep features considered artefacts related to off-profile features. Furthermore, the inversion of synthetic models provided support to the geological interpretation of the recovered anomalies for the 2D and 3D modelling. The 2D and 3D inversion models were similar above the sedimentary basins and showed marked differences above the Mérida Andes, due to the 3D nature of this section. The inversion models show electrically conductive basins with depths of 2 to 5 km for the Barinas-Apure and 2 to 9 km for the Maracaibo basins. Many resistive bodies within the Maracaibo basin could be related to active deformation causing juxtaposition of older geological formations and younger basin sediments. A conductive zone under the Maracaibo Basin correlates spatially with the location of a Bouguer anomaly low and seem to describe the SE tilt of the Maracaibo Triangular Block under the Mérida Andes. This conductive zone is limited towards the mountain by the north-western thrust system, whose fault plane may function as a detachment surface reaching depth larger than 30 km in the 3D inversion models. The most prominent fault systems of the area, the Boconó and Valera Faults, cross-cut the Mérida Andes in NE-SW direction along its strike with a length 400 km and N-S direction at its centre with a length 60 km, respectively. Both faults are associated with sub-vertical zones of high electrical conductivity and sensitivity tests suggest that the Valera fault reach depths of up to 12 km. The Boconó fault can be considered a crustal structure with a depth up to 35 km. The observed anomalies seem to show a deep connection of the fault planes, possibly related to the formation of the fault systems in a transpressive regime. Conductive anomalies to the south of the Boconó Fault seem to represent a considerable back thrust structure well constrained between 3 and 10 km depth. The high conductivity of these structures is possibly related to weathering water from the surface and the accumulation of clay minerals in the fault gauges. However, fluids related to the flat and shallow subduction of the Caribbean Plate in north-western Venezuela could better explain the low resistivity of the deep structures (〉 15 km). A sizeable conductor at 50 km depth, which appears consistently in the 2D sections, could be identified as an inversion artefact caused by a conductor east of the profile. The 3D inversion places this structure 10 km to the east at 15 km deep. This model also shows depth connection (12 km depth) of the anomalies related to the Valera and Boconó faults with the off-profile conductor. The observed anomalies in the 2D and 3D inversion related to these conductors were tested and reproduced employing synthetic datasets, leading to the speculation that the high conductivity associated with the off-profile conductor may be related to the detachment of the Trujillo Block. The models obtained confirm the shape and distribution of the known geological structures related to the complicated geodynamic settings responsible for the formation of the Mérida Andes. These results partially support the "floating orogen hypothesis" developed to explain the geodynamic evolution of western Venezuela, and they highlight the relevance of the Trujillo Block in this process. However, they also show that features of known structures such as the Boconó fault system maximum depth, the back-thrusting in the Mérida Andes, and the relevance of the escape of the Trujillo Block in the tectonic processes need to be adjusted to the current knowledge.

Description: Die Karibische und Südamerikanische tektonischen Platten begrenzten die nordöstliche Abschiebung des Nord-Anden-Blocks im Westen Venezuelas. Diese komplizierte geodynamische Umgebung führte zur Bildung großer Blattverschiebungen-Verwerfungssysteme und beträchtlicher Gebirgsketten. Die 100 km breiten Mérida-Andes erstrecken sich von der Grenze zwischen Kolumbien und Venezuela bis zum Coastal Cordillera. Im Norden und Süden sind die Mérida-Anden von kohlenwasserstoffreichen Sedimentbecken umgeben. Das Wissen über lithosphärische Strukturen im Zusammenhang mit der Bildung der Mérida-Anden ist jedoch aufgrund des Mangels an tiefen geophysikalischen Daten begrenzt. Diese Arbeit präsentiert die Ergebnisse des ersten breitbandigen magnetotellurischen Profils, das die Mérida-Anden und die Vorlandbecken Maracaibo und Barinas-Apure über eine Entfernung von 240 km quert. Der MT-Datensatz besteht aus 72 Stationen, die im März und April 2015 mit einer Mindestaufzeichnungsdauer von 3 Tagen pro Station installiert wurden. Geoelektrische Streich- und Dimensionalitätsanalysen stimmen mit ein- oder zweidimensionalen Untergrundstrukturen für die Sedimentbecken überein, weisen jedoch auch auf eine starke dreidimensionale Strukturen in der Umgebung der Mérida-Andes hin.. Noch wichtiger ist, dass diese Analysen das Vorhandensein von Merkmalen außerhalb des Profils zeigten, die die Daten insbesondere für lange Perioden erheblich beeinflussen. Daher war eine Kombination aus 2D- und 3D-Modellierung erforderlich, um Störungssysteme und Sedimentbecken quer zum Profil zu reproduzieren. Off-Profile-Strukturen können das Ergebnis einer 2D-Inversion erheblich beeinflussen. Daher war die systematische Untersuchung des Einflusses von 3D-Strukturen auf 2D-Inversionen erforderlich, um das erhaltene Ergebnis zu verifizieren. Synthetische Datensätze, die aus der 3D-Modellierung abgeleitet wurden, ermöglichten die Identifizierung und Quantifizierung von störenden Strukturen außerhalb des Profils sowie die Glättung von Artefakten aufgrund der begrenzten Stationsüberdeckung der entlang eines Profils gesammelten Daten. Im Allgemeinen werden Strukturen in der 2D-Inversion durch die Projektion und Rotation der Daten beeinflusst, was zu flach stehenden Anomalien führt, um die schräge Ausdehnung der Verwerfungssysteme und Sedimentbecken zu reproduzieren. Darüber hinaus kann ein Datensatz entlang eines Profils die laterale Auflösung einer 3D-Inversion erheblich einschränken. Daher wurde die Auswirkung der Datenverteilung auf eine 3D-Inversion sorgfältig untersucht, um die Bereiche der Modelle zu bestimmen, die durch die Daten sicher erklärt werden können. Zu diesem Zweck wurden mehrere synthetische Datensätze aus 3D-Modellen mit unterschiedlicher Komplexität abgeleitet. Die Analyse der synthetischen Datensätze ermöglicht die Bestimmung der lateralen Auflösung der 3D-Modelle und die Identifizierung von störenden oberflächennahen und tiefen Merkmalen, die als Artefakte im Zusammenhang mit Strukturen außerhalb des Profils betrachtet werden. Darüber hinaus unterstützte die Inversion synthetischer Modelle die geologische Interpretation der reproduzierten Anomalien für die 2D- und 3D-Modellierung. Die 2D- und 3D-Inversionsmodelle stimmen über den Sedimentbecken überein. Aufgrund der 3D Strukturen über den MA ergaben sich jedoch deutliche unterschiede. Die Inversionsmodelle zeigen elektrisch leitende Becken mit Tiefen von 2 bis 5 km für das Barinas-Apure und 2 bis 9 km für das Maracaibo-Becken. Viele Gebiete höheren Widerstands im Maracaibo-Becken könnten mit einer aktiven Deformation zusammenhängen, die ein Nebeneinander älterer geologischer Formationen und jüngerer Beckensedimente verursacht. Eine besserleitende Zone unter dem Maracaibo-Becken korreliert räumlich mit der Lage einer Bouguer-Anomalie und scheint die SE-Neigung des Maracaibo-Dreiecksblocks unter den Mérida-Anden zu markieren. Diese leitende Zone ist in Richtung des Gebirges durch das nordwestliche Schubsystem begrenzt, dessen Störungsebene als Ablösefläche fungieren kann, die in den 3D-Inversionsmodellen eine Tiefe von mehr als 30 km erreicht. Die bekanntesten Störungssysteme des Gebiets, die Verwerfungen Boconó und Valera, kreuzen die Mérida-Anden in Nordost-Südwest-Richtung entlang ihres Streichens mit einer Länge von 400 km und die N-S-Richtung in ihrer Mitte mit einer Länge von 60 km. Beide Störungen sind durch steil stehende Zonen hoher elektrischer Leitfähigkeit verbunden. Sensitivitätsstudien legen nahe, dass die Valera-Störung Tiefen von bis zu 12 km erreicht. Die Boconó-Verwerfung kann als Krustenstruktur mit einer Tiefe von bis zu 35 km angesehen werden. Die beobachteten Anomalien scheinen eine tiefe Verbindung der Verwerfungsebenen zu zeigen, möglicherweise im Zusammenhang mit der Bildung der Verwerfungssysteme in einem transpressiven Regime. Leitfähige Anomalien südlich der Boconó-Verwerfung scheinen eine beträchtliche Rückschubstruktur darzustellen, die zwischen 3 und 10 km Tiefe gut lokalisiert ist. Die hohe Leitfähigkeit dieser Strukturen hängt möglicherweise mitWasser aus Verwitterungsprozessen nahe der Erdoberfläche und der Ansammlung von Tonmineralien in den Störungszonen zusammen. Alte Fluide im Zusammenhang mit flach stehenden und oberflächenahen Subduktion der Karibikplatte im Nordwesten Venezuelas könnten jedoch den geringen spezifischen Widerstand der tiefen Strukturen (〉 15 km) besser erklären. Ein beträchtlicher Leiter in einer Tiefe von 50 km, der in den 2D-Schnitten konsistent erscheint, konnte als Inversionsartefakt identifiziert werden, der durch einen Leiter östlich des Profils verursacht wird. Durch die 3D-Inversion wird diese Struktur 10 km östlich in 15 km Tiefe platziert. Dieses Modell zeigt auch die Tiefenverbindung (12 km Tiefe) der Anomalien im Zusammenhang mit den Störungen von Valera und Boconó mit dem Leiter außerhalb des Profils. Die beobachteten Anomalien in der 2D- und 3D-Inversion in Bezug auf diese Leiter wurden unter Verwendung synthetischer Datensätze getestet und reproduziert. Daher kann man annehmen das die mit dem Leiter abseits des Profils verbundene Leitfähigkeit mit der Ablösung des Trujilo Blocks zusammenhängt. Die erhaltenen Modelle bestätigen die Form und Verteilung der bekannten geologischen Strukturen im Zusammenhang mit dem komplizierten geodynamischen Millieu, welches für die Bildung der Mérida-Andes verantwortlich ist. Diese Ergebnisse stützen teilweise die "schwimmende Orogenhypothese", die entwickelt wurde, um die geodynamische Entwicklung West-Venezuelas zu erklären, und sie unterstreichen die Relevanz des Trujillo-Blocks in diesem Prozess. Sie zeigen jedoch auch, dass Merkmale bekannter Strukturen wie die maximale Tiefe des Boconó-Verwerfungssystems, das Zurückschieben in den Mérida-Anden und die Relevanz des Entweichens des Trujillo-Blocks in den tektonischen Prozessen an den aktuellen Kenntnisstand angepasst werden müssen.

Description: This dataset provides friction and elasticity data from ring shear and axial tests, respectively, on rock analogue materials used at the University Roma Tre (Rome, IT) in “Foamquake”, a novel seismotectonic analog model mimicking the megathrust seismic cycle (Mastella et al., under review). Two granular materials (quartz sand and Jasmine rice) have been characterized by means of internal friction coefficients µ and cohesions C. An elastic material (foam rubber) have been characterized by means of Young’s modulus E and Poisson’s ratio v. According to our analysis the granular materials show Mohr-Coulomb behaviour characterized by linear failure envelopes in the shear stress vs. normal load Mohr space. Peak, dynamic and reactivation friction coefficients of the quartz sand are µP = 0.69, µD = 0.56 and µR = 0.64, respectively. Cohesion ranges between 50 and 100 Pa. Rate-dependency of friction in quartz sand seems insignificant. Peak, dynamic and reactivation friction coefficients of the Jasmine rice are µP = 0.70, µD = 0.59 and µR = 0.61, respectively. Cohesion ranges between 30 and 50 Pa. Rate-weakening of Jasmine rice is c. 6% per tenfold change in shear velocity v. The Young’s modulus of the foam rubber has been constrained to 30 kPa, its Poisson’s ratio is v=0.1.

Description: This dataset includes particle image correlation data from 26 experiments performed with Foamquake, a novel analog seismotectonic model reproducing the megathrust seismic cycle. The seismotectonic model has been monitored by the means of a high-resolution top-view monitoring camera. The dataset presented here represents the particle image velocimetry surface velocity field extracted during the experimental model through the cross-correlation between consecutive images. This dataset is supplementary to Mastella et al. (2021) where detailed descriptions of models and experimental results can be found.

Description: Earth angular momentum forecasts are naturally accompanied by forecast errors that typically grow with increasing forecast length. In contrast to this behavior, we have detected large quasi-periodic deviations between atmospheric angular momentum wind term forecasts and their subsequently available analysis. The respective errors are not random and have some hard to define yet clearly visible characteristics which may help to separate them from the true forecast information. These kinds of problems, which should be automated but involve some adaptation and decision-making in the process, are most suitable for machine learning methods. Consequently, we propose and apply a neural network to the task of removing the detected artificial forecast errors. We found, that a cascading forward neural network model performed best in this problem. A total error reduction with respect to the unaltered forecasts amounts to about 30% integrated over a 6 day forecast period. Integrated over the initial 3 day forecast period, in which the largest artificial errors are present, the improvements amount to about 50%. After the application of the neural network, the remaining error distribution shows the expected growth with forecast length. However, a 24 hourly modulation and an initial baseline error of 2*10−8 became evident that were hidden before under the larger forecast error.

Description: Understanding how resilient rangelands are to climatic disturbances such as drought is of major importance to land managers. The resilience of ecosystems can be reduced by livestock grazing and by environmental conditions. Most studies quantifying resilience are based on model simulations. However, natural time series from satellite data offer the possibility to infer aspects of resilience from real systems. The objective of this study was to investigate two aspects of ecological resilience, namely resistance to climate variability and recovery from drought, by applying a change detection method (Breaks For Additive Seasonal and Trend; BFAST) spatially on a 28-year Landsat NDVI time series in a dry rangeland in southern Cyprus. First, we used the number of breakpoints fitted by the BFAST model as an inverted proxy for long-term vegetation resistance to climate variability (the ability to withstand change during a disturbance reduces the likelihood to trigger a breakpoint in the time series). Second, we used the linear slope of the BFAST model after a known drought as a proxy of the recovery rate of the vegetation. This information was then used to analyse the spatial distribution of the total number of breakpoints and of the NDVI recovery trend in relation to grazing and environmental properties. Our results show that high NDVI and a northern orientation (i.e. favourable environmental conditions) were associated with a highly resilient system, due to high resistance to climate variability and fast recovery after drought. Intermediate conditions were associated with low resistance. Unfavourable conditions and high grazing intensities were associated with an unresponsive ecosystem state characterised by high resistance and slow recovery after a drought event. Low grazing intensities positively affected the NDVI recovery trend, but did not improve resistance. On northern slopes, terrain slope had a positive effect on the NDVI recovery trend, while on southern slopes it had a negative effect. Our satellite-driven approach has a strong potential for resilience monitoring, because it can be applied on broad spatial and temporal scales in areas with low availability of field data. Moreover, it allows to jointly extract two important components of resilience: resistance and recovery rate.

Description: Nutrient supply to the coastal euphotic zone is critical in sustaining the productivity of ecosystems and provides an important feedback on the carbon cycle via stimulating the biological pump. The supply of coastal nutrients is typically thought to be dominated by terrestrial inputs and upwelling of deep ocean waters. Marine-terminating glaciers can provide nutrients via both mechanisms but the relative importance of each is dependent on complex physical–biogeochemical processes ranging from those in the glacier drainage system to the ice–ocean interface. Constraining these glacial nutrient supply processes in a remote part of the Canadian Arctic Archipelago (CAA) is the focus of a new study by Williams et al. (2021, https://doi.org/10.1029/2021JG006289). Their findings advance our understanding of the role glaciers play in polar nutrient cycling by highlighting significant shallow meltwater pumping of macronutrient-replete marine waters by CAA marine-terminating glaciers into the euphotic zone.

Description: Earthquakes are generally known to alter the stress field near seismogenic faults. Observations using YRY-four-gauge borehole strainmeters within Yushu (YSH) borehole near the Ganzi-Yushu fault in eastern Tibetan Plateau shows that the azimuth variation of maximum horizontal stress (SH) first decreased and then increased substantially when the earthquakes occurred during the measurement period from January 1, 2009 to December 31, 2018. In this period, 38 earthquakes (M ≥ 3) were detected near the fault and the SH orientation showed a drastic change after the 2010 Ms 7.3 Yushu mainshock. We present a discrete element modelling using Particle Flow Code 2D (PFC2D) to simulate a dynamic fault rupturing process and to use the modelling results for interpretation of the stress reorientation. The modelling reveals that dilatation and compression quadrants are formed around a fault rupturing in strike-slip model, resulting in different spatiotemporal changes of the orientation of maximum horizontal stress (Δθ). The value of Δθ in the compression quadrants shows a sharp drop at the time of coseismic slip, then approaches slowly to an asymptotic value. In the dilatation quadrants, Δθ drops by coseismic slip, then increases sharply and finally reaches a stable value. The modelled Δθ by coseismic fault slip agrees with in-situ observations at YSH borehole during 2010 Ms 7.3 Yushu mainshock. It is also found that, the value of Δθ decreases with increasing distance from the rupturing source. We modelled the effect of fault geometry and host rock properties on the Δθ, and found that structural complexity and off-fault damage by coseismic fault slip have significant impact on the stress field alteration near the rupturing source.

Description: Fluid-induced seismicity in tectonically inactive regions has been attributed to fluid overpressurization of rock fractures during natural resource extraction and storage. We conducted a series of triaxial shear-flow experiments on sawcut fractures in granite and showed that the fracture responses can be dissimilar under various fluid pressurization conditions. For pressure-controlled fluid pressurization, a uniform fluid pressure distribution can be promoted by lowering pressurization rate and enhancing fracture permeability. However, during volume-controlled fluid pressurization, a high pressurization rate causes a drastic increase in fluid pressure before fracture failure. In this case, our analytical model reveals that the fracture area and normal stiffness also influence fluid pressure variations. The maximum seismic moment predicted by this model is well validated by the experimental data for the cases with low pressurization rates. The discrepancy between the analytical and experimental data increases with higher fluid overpressure ratio owing to the assumption of uniform fluid pressure distribution in the model. The sensitivity analysis demonstrates the importance of fracture size estimation in the maximum seismic moment prediction. Our model can potentially be applied to control the fluid overpressurization of rock fractures and to mitigate the risks of fluid-induced seismicity.

Description: Combining in situ measurements of energetic electrons and remote sensing observations of hard X-rays and type III radio bursts, we examine the release times of energetic electrons in the July 23, 2016 event. We find that the releases of in situ energetic electrons from the Sun are delayed from those electrons that are responsible for the hard X-rays. We further find that the release time of in situ electrons is a function of electron energy. Under the assumption that the acceleration mechanism for the upward propagating electrons is of Fermi-type and is controlled by an energy-dependent diffusion coefficient, we fit these release times by a simple functional form, related to the turbulence spectral index. Implications of our study on the underlying electron acceleration mechanisms and the magnetic reconnection process in solar flares are discussed. Our results demonstrate the power of the recently developed fractional velocity dispersion analysis (FVDA) method in solar flare studies.

Description: The equilibrium oxygen isotope fractionation factor between calcite and water (18αcalcite/H2O) is an important quantity in stable isotope geochemistry and allows in principle to infer temperature variations from carbonate δ18O if carbonate formation occurred in thermodynamic equilibrium. For this reason, many studies intended to determine the value of the oxygen isotope fractionation factor between calcite and water (18αcalcite/H2O) for a wide range of temperatures using modern cave calcite and the corresponding cave drip water or ancient speleothem carbonate and fluid inclusion samples. However, the picture that emerges from all of these studies indicates that speleothem calcite is not formed in thermodynamic equilibrium but under kinetic conditions, provoking a large variability of determined 18αcalcite/H2O values. Here we present a conceptual framework that can explain the variability of 18αcalcite/H2O values obtained by cave studies. Prior calcite precipitation (PCP) is calcite precipitation before cave drip water is dripping from the cave ceiling and impinges on the surface of a stalagmite or watch glass. Prior to the karst water dripping from the cave ceiling, PCP can occur in the karst above the cave as well as on the cave ceiling, the cave walls and on the surface of stalactites. We argue that PCP leads to increasing the δ18O value of the dissolved HCO3- (δ18OHCO3-), resulting in an oxygen isotope disequilibrium of the δ18OHCO3- values with respect to the δ18O value of water (δ18OH2O). The oxygen isotope disequilibrium between HCO3- and H2O is re-equilibrated by oxygen isotope exchange between H2O and HCO3. Depending on the temperature, the re-equilibration time varies from hours to days and is usually much longer than the residence time of the drip water on stalactites, but much shorter than the time required to percolate through the karst. Therefore, while the oxygen isotope equilibrium between HCO3- and H2O is very likely re-established when PCP occurred in the karst, oxygen isotope disequilibrium conditions between HCO3- and H2O still prevail when PCP occurred inside a cave, e.g., on stalactites. If the oxygen isotope disequilibrium conditions between HCO3- and H2O is not re-established, the precipitated calcite will inherit the elevated δ18O value of the HCO3- and not be in oxygen isotope equilibrium with the corresponding drip water. Consequently, if the 18αcalcite/H2O value is calculated from cave calcite samples affected by PCP, the derived value will be systematically biased.

Description: Globally, mountain systems are unevenly exposed to risks of extreme precipitation. Within the Himalayan region, precipitation extremes are a rising concern, but their current understanding is limited. In this study, we use 113 years of precipitation data to rank and characterize precipitation extremes in the Indian Western Himalayas (IWH). Our statistical ranking method integrates precipitation spatial extent and its intensity across different durations for determining the severity of extreme events. The proposed ranking method accounts for multi-day duration ranking method to capture persistent precipitation episodes. Results show that the method accurately detects and ranks the most extreme precipitation events that occurred in the IWH and indicate locations of these events. Our results highlight that critical long duration events in the region (e.g., 10 days) are missed at ranks at shorter duration (e.g., 2–3 days), thereby highlighting the importance to multi-day precipitation extremes ranking. In addition, the proposed ranking method provides information about the event duration that will be associated with the highest impact on society, carrying high significance. Our findings are valuable for flood risk management and disaster risk reduction.

Description: Increasingly accurate, and spatio-temporally dense, measurements of Earth surface movements enable us to identify multiple deformation patterns and highlight the need to properly characterize the related source processes. This is particularly important in tectonically active areas, where deformation measurement is crucial for monitoring ongoing processes and assessing future hazard. Long Valley Caldera, California, USA, is a volcanic area where frequent episodes of unrest involve inflation and increased seismicity. Ground- and satellite-based instruments show that volcanic inflation renewed in 2011, and is continuing as of early 2021. Additionally, Long Valley Caldera is affected by the large, but spatially and temporally variable, amounts of precipitation falling on the adjacent Sierra Nevada Range. The density and long duration of deformation measurements at Long Valley Caldera provide an excellent collection of data to decompose time-series and separate multiple superimposed deformation sources. We analyze Global Navigation Satellite System (GNSS) time-series and apply variational Bayesian Independent Component Analysis (vbICA) decomposition method to isolate inflation-related signals from other processes. We show that hydrological forcing causes significant horizontal and vertical deformation at different temporal (seasonal and multiyear) and spatial (few to hundreds of km) scales that cannot be ignored while analyzing and modeling the tectonic signal. Focusing on the last inflation episode, we then improve on prior simplistic models of the inflation reservoir by including heterogeneous subsurface material properties and topography. Our results suggest the persistence and stability of the reservoir (prolate ellipsoid at about 8 km beneath the resurgent dome) and indicate a 40-50% reduction of the inflation rate after about 3 years from the inflation onset. The onset of the reduced inflation rate corresponded in time with the occurrence of a strong seismic swarm in the Caldera, but also to the temporal variation of climatic conditions in the area.

Description: At the Decatur carbon capture and storage site (IL, USA) CO2 has been injected from 2011–2014 and from 2017 to present near the base of the Lower Mt. Simon Sandstone saline reservoir, resulting in microseismicity. Microseismicity is mainly located in the basement and distributed in distinct spatial clusters. The lack of significant impedance contrasts within the basement makes the interpretation of active-source seismic reflection data challenging, however, recent reprocessing allowed to resolve faults above and at the top of the basement. These faults generally do not coincide with the location of microseismic events and their continuation to the general depth of the seismic events cannot be assumed. This paper shows how the interpretation of the microseismicity can complement structural interpretations of active-source seismic reflection data. In particular, we analyze clusters and bursts (abrupt increases) of microseismicity, identify unresolved, smaller-scale weaknesses and extract statistical parameters. These parameters allow comparisons with the interpreted faults, and with fracture sets intercepted by boreholes. During injection at the Decatur site, the injection pressure was kept far below fracture pressure, nevertheless, seismic events were induced and spread far beyond the expected extent of the CO2 plume. We argue that local stress transfers related to the CO2 injection reactivated pre-existing fractures within the critically stressed basement. Finally, we conducted a slip tendency analysis for faults interpreted from active seismic, selected cluster, bursts and nodal planes from focal mechanisms to determine if the interpreted structures are optimally oriented with respect to the stress regime. Our results suggest that the orientation of fractures close to the injection well, generally shows slight deviations from the optimal orientation for slip. This might indicate either slight local deviations of the maximum horizontal stress azimuth from the average direction used in the analysis, or the lack of optimally oriented fractures at this location.

Description: Reconstruction and prediction of the state of the near-Earth space environment is important for anomaly analysis, development of empirical models, and understanding of physical processes. Accurate reanalysis or predictions that account for uncertainties in the associated model and the observations, can be obtained by means of data assimilation. The ensemble Kalman filter (EnKF) is one of the most promising filtering tools for nonlinear and high dimensional systems in the context of terrestrial weather prediction. In this study, we adapt traditional ensemble-based filtering methods to perform data assimilation in the radiation belts. By performing a fraternal twin experiment, we assess the convergence of the EnKF to the standard Kalman filter (KF). Furthermore, with the split-operator technique, we develop two new three-dimensional EnKF approaches for electron phase space density that account for radial and local processes, and allow for reconstruction of the full 3D radiation belt space. The capabilities and properties of the proposed filter approximations are verified using Van Allen Probe and GOES data. Additionally, we validate the two 3D split-operator Ensemble Kalman filters against the 3D split-operator KF. We show how the use of the split-operator technique allows us to include more physical processes in our simulations and is a computationally efficient data assimilation tool that delivers an accurate approximation of the optimal KF solution, and is suitable for real-time forecasting. Future applications of the EnKF to direct assimilation of fluxes and nonlinear estimation of electron lifetimes are discussed.

Description: This work presents a study of an unusual synthetic diamond sample, where calcite is the main phase in addition to diamond. Using Raman spectroscopy it can be shown that in addition to diamond carbon forms four different generations: highly ordered graphite-II, lower ordered graphite-I as spandrel between different mineral grains, weakly-ordered carbonaceous material as graphite-III and the hexagonal diamond lonsdaleite (here graphite-IV) as last formation in calcite. Graphite-III can be found mainly in the calcite body. According to the fine dispersion of this carbonaceous material and the arrangement on grain boundaries, we assume that carbon was dissolved in the calcite melt, and that by the activated state of carbon in the calcite melt the formation of diamond is favored near 1760°C, and 6.8 GPa. Lonsdaleite as minor phase may have been formed as an longlived intermediate state under standard conditions between graphite and diamond. Evidence shows that there are two different lonsdaleite phases (possibly hexagonal and monocline) present. The prevailing diamond is characterized by the first-order Raman line at 1333 cm-1. However, there are also present diamonds with the first-order Raman line down to 1310.6 cm-1, corresponding to 13C = 0.511. Significantly there is the strong decrease of the optical damage threshold with increase of the 13C content.

Description: The Earth's radiation belts include electrons over a wide energy range. The dynamics of electrons can differ significantly, depending on the energy. In comparison to ~MeV energies, multi-MeV electrons are less predictable during geomagnetic storms [1], as their population can be depleted, enhanced, or remain unchanged, with nearly equal probability [2]. The depletion of electrons can be reversible (adiabatic) or irreversible, due to wave-particle interactions and loss at the outer boundary. Nonadiabatic changes can be identified by analyzing phase space density (PSD) as a function of the three adiabatic invariants. Fast-localized losses, such as interaction with electromagnetic ion cyclotron (EMIC) waves, can produce deepening PSD minima [3]. The EMIC waves are very effective in scattering multi-MeV electrons and can create sharp gradients in pitch angle distributions, although they do not resonate with nearly equatorial mirroring electrons. The depletion of electrons in a wide range of pitch angles occurs with assistance of the hiss and chorus waves [4]. However, the local minimum in PSD may be also observed due to outward radial diffusion with either subsequent refilling of the radiation belts or local acceleration. In this case, the formation of the minima will not result in continued deepening [5].

Description: Loading and unloading effects of the Scandinavian Ice Sheet triggered halotectonic movements in Northern Germany. We present newly detected geomorphological features—termed surface cracks—which indicate a relation between ice sheet-induced salt movement and surface processes. As a part of the Central European Basin System, numerous Zechstein salt structures are abundant in the North German Basin. On the basis of high-resolution digital terrain data, more than 160 surface cracks were mapped in Northern Germany, which were grouped into 30 clusters. Almost all of the surface cracks occur above the top regions of Zechstein salt structures. The surface cracks can be several kilometres long, up to more than 20 m deep and more than 100 m wide. The comparison of the shape of the salt structures and the orientation of the cracks reveals a geometric dependency, indicating that the cracks preferably occur near the crest margins of the salt structures. Furthermore, 3D seismic data from two sites show that subsurface faults originating from salt movement exist beneath the surface cracks. We interpret the cracks as surface ruptures due to ice sheet-induced halotectonic movements. The cracks occur in a variety of Quaternary sediments and landforms. This indicates that widespread halokinetic movements occurred in the region after the last (Weichselian) deglaciation and likely before the thawing of the permafrost, possibly in a time frame from c. 30–20 ka until c. 15 ka.

Description: While there has been a lot of work focusing on improving our understanding of divergent and convergent plate boundaries, the intricate nature of back-arc extension, where subduction and large-scale extension occur and interact in close, is yet to be explored properly. It has long been proposed that the strength of the subduction interface, which depends among others on the amount of subducted sediments, plays a pivotal role in subduction dynamics. Here, we investigate the role of back-arc rheology and subduction interface strength on the deformation style of the overriding plate. Using two-dimensional thermomechanical model experiments, we demonstrate, that the presence of a weak mantle–lithospheric domain in the overriding plate can result in back-arc breakup even during the subduction of narrow, land-locked oceanic basins such as those found in the Mediterranean region. The thinning of the back-arc mantle–lithosphere results in a weaker overriding plate, hence a lower slab-pull force is sufficient to initiate back-arc extension. Convective thinning at the subduction interface also reduces the length of the interface, reducing the portion of slab-pull lost as energy dissipation. A weak plate interface, can also reduce the energy dissipated along the subduction zone, leading to earlier extension. A detailed analysis of the forces shaping the overriding plate stress field shows that transmission of slab-pull force has a predominant role while viscous basal drag has a negligible effect in our experiments. Our results compare favorably with large-scale characteristics of land-locked Mediterranean back-arc basins such as the North Tyrrhenian basin and the Pannonian basin.

Description: Marine oil spills are among the most significant sources of marine pollution. Synthetic aperture radar (SAR) has been used to improve oil spill observations because of its advantages in oil spill detection and identification. However, speckle noise, weak boundaries, and intensity inhomogeneity often exist in the oil spill regions of SAR imagery, which will seriously affect the accurate identification of oil spills. To enhance marine oil spill segmentation of SAR images, a fast, edge-preserving framework based on the distance-regularized level set evolution (DRLSE) model was proposed. Specifically, a bilateral filter penalty term is designed and incorporated into the DRLSE energy function (BF-DRLSE) to preserve the edges of oil spills, and an adaptive initial box boundary was selected for the DRLSE model to reduce the operation time complexity. Two sets of RadarSat-2 SAR data were used to test the proposed method. The experimental results indicate that the bilateral filtering scheme incorporated into the energy function during level set evolution improved the stability of level set evolution. Compared with other methods, the proposed improved BF-DRLSE algorithm displayed a higher overall segmentation accuracy (97.83%). In addition, using an appropriate initial box boundary for the DRLSE method accelerated the global search process, improved the accuracy of oil spill segmentation, and reduced computational time. Therefore, the results suggest that the proposed framework is effective and applicable for marine oil spill segmentation.

Description: Located in the middle of Shanxi Province, northern China, Taiyuan basin is a dry and water-short region. This region is reaching alarming levels of aquifer depletion due to decades of groundwater overexploitation, which has caused severe land subsidence in the basin. The Wanjiazhai Water Diversion Project (WWDP) was designed to ease water scarcity by transporting water from the Yellow River to the Taiyuan basin through 452.4 km-long canals. By the end of 2018, the WWDP had supplied 2.87 billion m3 of water to Shanxi Province, which replenish the basin’s surface water body as well as the underground aquifer. The groundwater levels have continued to rise since 2003, with rising levels of more than 70 meters by 2018 in comparison with its low stand in 2000. In this study, we use 2007-2010 ENVISAT, ALOS-1 data, and 2017-2020 Sentinel-1 data to study the response of the basin’s aquifer to the groundwater rebound against the background of the water transfer project. We addressed the issue of tropospheric delay and its impact on the seasonal deformation by combing GACOS (Generic Atmospheric Correction Online Service) and a common-point stacking method. The accuracy improvement of deformation by this correction method was validated with measurements from seven continuous GPS stations in the basin. Groundwater rebound triggers ground uplift, which was identified in five areas by InSAR with a rate up to 25 mm/yr. The uplifting displacement time series are well correlated with groundwater level recovery. The land subsidence in the south of the basin continues but the rates decreased significantly in 2017-2020 detected from Sentinel-1 as compared to that in period 2007-2010 from ENVISAT and ALOS-1. All these uplifting signals and the decreasing rates of land subsidence found in Taiyuan city provide the indication that water management practices are successful in mitigating further subsidence. We found a significant seasonal displacement concentrated within the central region of the basin corresponding to the main irrigated areas in the Taiyuan basin. The maximum peak-to-peak amplitude is 43 mm observed from ENVISAT and decreases to 20 mm observed from Sentinel-1. The seasonal amplitudes change rapidly across faults, indicating that the fault is an effective barrier to across-fault fluid flow. To further quantify the causal relationships between water level and ground displacement, groundwater levels and ground displacement at three wells located near the area affected by significant seasonal land subsidence are analyzed by Cross Wavelet Transform (XWT) method. We found the time lags of about one month between land subsidence and the forcing groundwater level declines. Such a cross wavelet analysis with high spatial-temporal resolution therefore enables tracking the health of the aquifer system and highlights the system’s sustainability in aiding water resources allocation against the background of the water diversion project.

Description: Die ORCID iD hat sich zum internationalen De-facto-Standard für die eindeutige und persistente Identifikation sämtlicher an Forschungs- und Publikationsprozessen beteiligten Personen in der Wissenschaftscommunity etabliert. Die international agierende Non-Profit-Organisation ORCID Inc. vernetzt weltweit über 12 Millionen ORCID iDs mit ihren Forschenden. Um ORCID in Deutschland zu fördern, wurde das Projektvorhaben ORCID DE initiiert. Im vorliegenden Beitrag wird der Dienst ORCID und seine Implementierungsmöglichkeiten anhand von praktischen Beispielen aus Wissenschaftsorganisationen in Deutschland beschrieben und die Notwendigkeit der Autor*innendisambiguierung hervorgehoben.

Description: Receiver function. Response of the Earth’s structure below seismic stations to incident teleseismic waves. Seismic discontinuities in the Earth’s crust or upper mantle cause waves from distant earthquakes to be converted from P to S waves or vice versa or to be multiply reflected between discontinuities before arriving the stations. Such scattered waves carry information about the seismic structure of the lithosphere and upper mantle. Scattered waves are weak signals, and summation of many records is usually required to visualize the useful information.

Description: We explore nonlinear site effects in the new Japanese ground-motion dataset compiled by Bahrampouri et al. (2020). Following the approach of Seyhan and Stewart (2014), we evaluate the decrease of soil amplification according to the increasing and corresponding ground motion on surface rock (VS30 760 m=s). To better predict the rock ground motion associated with each record, we take into account the between-event variability of the ground motion, and to better evaluate the impact of nonlinearity, we correct observed ground motion on soil by the site-specific linear amplification. Instead of grouping the stations by site-response proxy, we focus on individual stations with several strong-motion records. We develop a framework to test recently published nonlinear site amplification models against a linear site amplification model and compare the results with recent building codes that include nonlinearity. The results show that the site response varies greatly from site to site, indicating that conventional site proxies, such as VS30, are not sufficient to characterize nonlinear site response. Out of all of the Kiban–Kyoshin network stations, 20 stations are selected as having recorded sufficient data to be used in the test. Out of these 20 stations, five stations show signs of nonlinearity, that is, the nonlinear models performed better than the linear-amplification model for all periods T. For most sites, however, the linear site amplification models get the best score. This suggest that, for the range of predicted rock motion considered in this study (peak ground acceleration 〈0:2g), nonlinearity may not have a sufficiently large impact on soil ground motion to justify the use of nonlinear site terms in ground-motion functional forms and seismic building codes for such moderate-level shaking.

Description: The cosmogenic meteoric 10Be that is produced in the atmosphere and mainly scavenged by rainfall is a valuable tool for determining dates and rates of Earth surface processes. A key prerequisite for its applications is the knowledge of the long-term 10Be depositional flux to Earth's surface. Previous efforts on obtaining 10Be depositional fluxes include general atmospheric circulation modelling (GCM), empirical fitting of rainfall 10Be records, and determining the inventory of soil profiles of known age. Here, we derive 10Be depositional fluxes from Holocene river terrace 10Be inventories across the Taiwan mountain belt. We measured 10Be and 9Be concentrations from three terrace profiles, with 14C ages ranging between 3.83 and 9.05 cal. kyr BP and sampling depths of up to 6.2 m. Based on 10Be inventories of our river terraces, the calculated long-term 10Be depositional fluxes vary from 0.32 to 0.49 × 106 at/cm2/yr in the Taiwan orogen. We identify partial Be retention, surface erosion, multi-phase sediment deposition, and incomplete sampling depth in these terraces as potential causes of flux underestimation. When accounting for each of these factors and their uncertainties, the resulting flux estimates of each terrace show an overlapping range of 0.66–0.88 × 106 at/cm2/yr. This newly constrained flux range representative over millennial timescales is thus recommended for Earth surface applications in the fast-eroding Taiwan orogen, especially in regions with similar climatic conditions as the studied terraces. When comparing to flux estimates from other approaches, the flux from the rainfall-based fitting equation exceeds our new terrace-derived flux by more than a factor of two. We consider such high flux to be unlikely for the Taiwan orogen, and suggest that the control of precipitation on the 10Be flux here may be overestimated in rainfall data fitting. The GCM-derived flux overestimates the 10Be depositional flux in this setting to a smaller degree (at least 23%), which is in accordance with findings from previous global data compilation of 10Be fluxes.

Description: Liquid permeability of sedimentary rocks is relevant in several contexts, but gas permeability is easier to measure, so liquid permeability is typically estimated from gas permeability via empirical or semiempirical correction procedures. A frequently used and trusted procedure is the well-known Klinkenberg correction, which is based on the pressure dependence of gas permeability. However, from gaseous and liquid flow-through experiments on a series of Fontainebleau, Castlegate, Bentheim, and Obernkirchen sandstones, this study indicates that the equivalent liquid permeability derived from gas permeability via the Klinkenberg correction only compares with liquid permeability, when the gaseous flow adheres to Darcy’s law. The lower and upper limits to Darcy flow are defined by the Knudsen and Reynolds numbers, respectively. Both numbers can be estimated from porosity and pore-throat distribution, so from these properties, it is possible to assess the flow and pressure limits for the applicability of the Klinkenberg correction. For the studied sandstones, non-Darcy flow is indicated for the largest pores with diameters above approximately 10 μm, causing an erroneous Klinkenberg correction. Knudsen diffusion takes place in pores smaller than approximately 0.1 μm, but the contribution to the overall gas permeability of these small pores is, however, insignificant in these sandstones. Liquid permeability modeled from contributions from each pore size by using Kozeny’s equation and surface relaxation times from nuclear magnetic resonance data shows that the largest pores have no positive effect on permeability because of the existence of pore throats; instead, they may have a negative effect on permeability because of turbulence.

Description: Archaeomagnetic data are fundamental for our understanding of the evolution of Earth's magnetic field on centennial to millennial timescales. From the earliest studies of the Thelliers, Aitken, Nagata and others in the 1950s and 1960s, archaeomagnetic data have been vital for extending our knowledge of the field to times prior to observational measurements. Today, many thousands of archaeomagnetic data allow us to explore the geomagnetic field in more detail than ever before. Both regional time series of archaeomagnetic data and the inclusion of archaeomagnetic data in time-varying global spherical harmonic field models have revealed a range of newly discovered field behaviour. More sophisticated approaches to developing regional curves and global models have allowed us to resolve the field in certain regions more robustly and with greater resolution than previously possible. In this review we give an overview of the widely used global archaeomagnetic database GEOMAGIA50, discuss the methods used to obtain archaeomagnetic data, their challenges, and explore progress over the past twenty years in developing regional secular variation curves and global spherical harmonic models of the archaeomagnetic field. We end the review by covering what we see as the “grand challenges” in archaeomagnetism, including which regions of the world should be focussed on with regards to data acquisition.

Description: The Earth is rotating around its rotation axis in an irregular manner. The Earth rotation axis and its orientation in space vary with respect to the reference system (both the terrestrial and the celestial) due to the wide range of processes that contribute to the rotation excitation. Therefore, the study of the Earth rotation can provide essential information concerning the Earth system. Spaceborne geodetic sensors can determine Earth orientation parameters (EOP), which fully describe Earth’s behaviour in space. The EOP are needed for several fields and applications such as fundamental astronomical and geodetic reference systems, precise satellite orbit determination, space navigation, and disaster prevention.\\ Over the past three decades, climate change has caused undesirable alterations in living organisms, human activities, and socio-economic aspects. Climate change is fluctuating and alters weather patterns such as precipitation patterns and sea and ocean levels. It also threatens the biodiversity of ecosystems, food security, and human health, and exacerbates natural disasters. The intensity and frequency of natural hazards are increasing with erratic distribution due to changes in the climate. Also, the level of vulnerability and zonation of risk are changed. Analysis of natural hazards, such as atmospheric and hydrological events, can help improve crisis management. Therefore, satellite observation data and simulated data derived from different atmospheric models are needed in order to model different types of hazards and risks, which can help early warning and prediction systems. Even though continuous sensor measurements and archive data (historical data/climate) are used for weather forecasting in developed countries, deadly flooding happened close to Stuttgart in southern Germany in May 2016, which might be avoided by a precise weather warning system. Therefore, real-time space geodetic technique data estimation is necessary to use as input data in weather prediction models. For the analysis of space geodetic techniques in (near) real-time, predictions of the EOP are required. EOP are made available by the International Earth Rotation and Reference Systems Service (IERS) Rapid Service Prediction Centre at USNO, Washington D.C., with a delay of hours to days. Accordingly, in the past, several methods were developed and applied for the EOP prediction. However, the accuracy of EOP prediction is still unsatisfactory, even for prediction of just a few days in the future.\\ To improve the EOP prediction accuracy, this study investigates the consistency between Earth rotation’s theories and observations. Moreover, the potentials of different geophysical phenomena are examined to better understand the interaction of different processes that affect the Earth rotation excitation with the time. Most of the Earth’s rotation theories and solutions are based on the location of the Earth’s principal axes of inertia (PAI). That location is defined by the second-degree Stokes coefficients of the geopotential, which are accurately observed by the Gravity Recovery and Climate Experiment (GRACE) and satellite laser ranging (SLR). In this study, the evolution of the Earth’s axes of inertia is analyzed for the first time. The presented results are remarkable, as the inertia axes do not move around a mean position fixed to a given terrestrial reference frame in the study period, but drift away from their initial location in a non-negligible manner.\\ Moreover, this study proposes a novel hybrid approach to predict EOP. There is a well-introduced stochastic method called copula-based analysis, and I combined it with singular spectrum analysis (SSA) for EOP prediction. I analyzed the potential of copula-based methods for predicting Earth rotation parameters that are derived from the combination of different satellite geodetic sensors and from other geophysical parameters like effective angular momentums. The copula is a statistical method that exploits linear and non-linear relationships between two or more variables by fitting a theoretical copula function into an empirical bivariate or multivariate distribution function. I introduced a hybrid prediction method that can be applied to other geophysical parameters is introduced in this thesis.\\ In this study, the interconnection between the celestial pole motion (CPM) and geomagnetic field (GMF) is investigated to improve the current CPM prediction methods. During the last decade, several investigations have been conducted in order to discuss a possible interconnection of polar motion and geomagnetic jerks, which are rapid changes in GMF secular variations. However, less attention has been paid to the impact of the GMF changes on the CPM, e.g., the interrelation of the geomagnetic jerks, geomagnetic dipole moment, geomagnetic field elements, and CPM variations. In this study, I use the CPM time series obtained from very long baseline interferometry (VLBI) observations and the latest GMF data to explore the correlation between CPM and the GMF. Our preliminary results revealed some impressive common features in the CPM and GMF variations, which show the potential to improve our understanding of the GMF’s contribution to the Earth’s rotation. All in all, the results mathematically illustrate the coherency between the GMF parameters and CPM, which helps improve EOP products.

Description: Die Erde dreht sich um ihre Rotationsachse auf unregelmäßige Art und Weise. Die Erdrotationsachse und ihre Orientierung im Raum variieren in Bezug auf das Referenzsystem (sowohl im terrestrischen wie auch im zälestischen System) aufgrund des breiten Spektrums von Prozessen, die zur Rotationsanregung beitragen. Daher kann die Untersuchung der Erdrotation wesentliche Informationen über das Erdsystem liefern. Weltraumgestützte geodätische Sensoren liefern Informationen über erdgebundene Orientierungsparameter (EOP), die das Verhalten der Erde im Weltraum vollständig beschreiben. EOP werden für verschiedene Bereiche und Anwendungen, wie beispielsweise für grundlegende astronomische und geodätische Referenzsysteme, benötigt. Des Weiteren sind sie auch für die präzise Bestimmung von Satellitenorbits und die weltraumgestützten Navigation, bis hin zu Anwendungen im Katastrophenschutz von Bedeutung.\\ In den letzten drei Jahrzehnten zeigen sich bereits die negativen Auswirkungen des Klimawandels auf Biosphäre, menschliche Aktivitäten und sozioökonomische Aspekte. Der Klimawandel unterliegt Fluktuationen und verändert die Wettermuster, wie z.B. die Niederschlagsverteilung, sowie Meeres- und Ozeanspiegel. Er bedroht aber auch die biologische Vielfalt der Ökosysteme, die Ernährungssicherheit, die menschliche Gesundheit und verschlimmert Naturkatastrophen. Die Intensität und Häufigkeit von Naturgefahren werden zunehmen, hierbei ist ihre Verteilung aufgrund von Klimaveränderungen allerdings unregelmäßig; auch der Grad von Schadensanfälligkeiten und die Einteilung von Risikozonen werden sich zukünftig ändern.\\ Die Analyse von Naturgefahren, wie atmosphärische und hydrologische Ereignisse, kann zur Verbesserung des Krisenmanagements beitragen. Daher werden Satellitenbeobachtungen und simulierte Daten, die von verschiedenen atmosphärischen Modellen abgeleitet werden, für die Gefahr- und Risikomodellierung benötigt; dies kann Frühwarn- und Vorhersagesysteme unterstützen. Obwohl kontinuierliche Sensormessungen und Archivdaten (historische Daten/Klimadaten) für die Wettervorhersage in entwickelten Ländern zur Verfügung stehen, kamen es im Mai 2016 in der Nähe von Stuttgart in Süddeutschland bei einer katastrophalen Überschwemmung zu Verlusten von Menschenleben, die möglicherweise durch ein präzises Wetterwarnsystem vermeidbar gewesen wären. \\ Eine Echtzeitschätzung der geodätischen Weltraumtechnik wäre notwendig, um sie als Eingangsdaten in Wettervorhersagemodellen zu verwenden. Für die Analyse von raumgeodätischen Techniken in (nahezu) Echtzeit sind Vorhersagen der EOP unerlässlich. EOP werden durch das Rapid Service Prediction Centre des International Earth Rotation and Reference Systems Service (IERS) am USNO, Washington D.C., mit einer Verzögerung von Stunden bis Tagen zur Verfügung gestellt. Demzufolge wurden in der Vergangenheit mehrere Methoden für die EOP-Vorhersage entwickelt und angewendet. Die Genauigkeit dieser EOP-Vorhersagen ist jedoch nach wie vor - selbst für einen Vorhersagezeitraum von nur wenigen Tagen - unbefriedigend.\\ Um die Genauigkeit der EOP-Vorhersage zu verbessern, beschäftigt sich die vorliegende Studie mit der Untersuchung von der Vereinbarkeit von Erdrotationstheorien mit Beobachtungen. Darüber hinaus wird das Potenzial verschiedener geophysikalischer Phänomene analysiert, um die Wechselwirkungen verschiedener Prozesse, die die zeitabhängige Anregung der Erdrotation beeinflussen, besser zu verstehen.\\ Die meisten Theorien und Lösungen zur Erdrotation basieren auf der Lage der Hauptträgheitsachsen der Erde (PAI). Diese Position wird durch die Stokes-Koeffizienten zweiten Grades des Geopotentials, das mit Hilfe der Satellitenmission Gravity Recovery and Climate Experiment (GRACE) und der Satelliten-Laser-Entfernungsmessung (SLR) genau beobachtet wird, definiert. In dieser Studie wird zum ersten Mal die Entwicklung der Trägheitsachsen der Erde analysiert. Bemerkenswert an den vorgestellten Ergebnissen ist, daß sich die Trägheitsachsen während der Untersuchungsperiode nicht um eine mittlere Position, die in einem bestimmten terrestrischen Bezugsrahmen festgelegt ist, bewegen, sondern sich in nicht zu vernachlässigender Weise von ihrem ursprünglichen Position entfernen.\\ Darüber hinaus schlägt diese Studie einen neuartigen hybriden Ansatz zur EOP-Vorhersage vor. Es gibt eine gut eingeführte stochastische Methode, die “kopula-basierte Analyse”, die wir mit der “Singulär-Spektrum-Analyse” (SSA) für die EOP-Vorhersage kombiniert haben . Wir analysierten das Potenzial kopula-basierter Methoden zur Vorhersage von Erdrotationsparametern, die aus der Kombination verschiedener geodätischer Satellitensensoren und aus anderen geophysikalischen Parametern, wie z.B effektiven Drehimpulsen, abgeleitet werden. Die Kopula ist eine statistische Methode, die lineare und nicht-lineare Beziehungen zwischen zwei oder mehreren Variablen nutzt, indem eine theoretische Kopula-Funktion an eine empirische, bivariate oder multivariate Verteilungsfunktion angepasst wird. Wir haben eine hybride Vorhersagemethode entwickelt, die auch auf andere geophysikalische Parameter angewendet werden kann.\\ In dieser Studie wird der Zusammenhang zwischen der Bewegung des Himmelspols (CPM) und dem geomagnetischen Feld (GMF) untersucht, um die derzeitigen CPM-Vorhersagemethoden zu verbessern. Während des letzten Jahrzehnts wurden mehrere Untersuchungen durchgeführt, um eine mögliche Verbindung zwischen polaren Bewegungen und geomagnetischen Ausbrüten - hierbei handelt es sich um rasche Veränderungen der säkularen Variationen des GMF - zu erörtern. Weniger Aufmerksamkeit wurde jedoch den Auswirkungen der GMF-Änderungen auf die CPM, z.B. der Wechselbeziehung der geomagnetischen Ausbrüte, des geomagnetischen Dipolmoments, der geomagnetischen Feldelemente und der CPM-Variationen, gewidmet. In dieser Studie verwenden wir CPM-Zeitreihen, die aus Beobachtungen der Very Long Baseline Interferometry (VLBI) gewonnen wurden und aktuelle GMF-Daten, um die Korrelation zwischen CPM und GMF zu untersuchen. Unsere vorläufigen Ergebnisse zeigen einige auffallente Gemeinsamkeiten in den CPM- und GMF-Variationen, die das Potenzial besitzen, unser Verständnis des GMF-Beitrags zur Erdrotation zu verbessern. Alles in allem veranschaulichen die Ergebnisse mathematisch die Kohärenz zwischen den GMF-Parametern und der CPM und weisen damit perspektivisch den Weg für eine Verbesserung der EOP-Produkte.

Description: Our planet is in crisis! The latest report of the United Nations Intergovernmental Panel on Climate Change (IPCC AR6) confirms that human influence is causing widespread, rapid, and intensifying changes in our weather and climate that are affecting every region on Earth in multiple ways. With every additional ton of carbon we emit, the frequency and intensity of storms, floods, droughts, and fires become greater and the effects on the environment and on human health and civilization become more severe. As geoscientists and journal editors, most of us have been accustomed to being on the leading edge of human knowledge and understanding of climate change, where we deal in objectivity, uncertainty, and debate, but now we find ourselves at the core of this climate crisis. It is no longer scientific discoveries at stake, but also humanity itself. This is an uncomfortable place for many of us. We are trained to be dispassionate observers and cautious thinkers, yet the alarming rate of recent climate change impels us to turn our attention directly toward mitigating this impending crisis. We are making a plea for collective action: we must make the switch to a green economy, put a just and effective price on carbon now, and consider a portfolio of other equitable public investments in climate solutions. These actions will ensure that the true costs and risks of burning fossil fuels are accounted for and global carbon emissions are rapidly reduced. Rich countries must lead the way in making drastic cuts to carbon emissions and in helping low- and middle-income countries to develop sustainably. We are running out of time. For decades, American Geophysical Union (AGU) journals have been at the forefront of documenting human-caused climate change and warning of a worsening climate crisis. Over 2,000 publications from AGU journals are cited in the new IPCC AR6 report. But we too can do more than just document and scientifically explain the ongoing crisis—our profession must help lead the way to solutions. Finding solutions and adapting to change have become not only necessary, but essential in ensuring safe, sustainable, and healthy human communities in the future. The geosciences have an essential role to play in these efforts by pivoting toward more cross-sector, solution-based science. To help lead this vision, the AGU is adding a new publication forum for community science in partnership with associations outside the geosciences. This forum will enhance interactions among AGU's existing, more disciplinary journals and give local communities a voice in leading solutions to global challenges. We are scientists, but we also have families and loved ones alongside our fellow citizens on this planet. The time to bridge the divide between scientist and citizen, head and heart, is now. The lead-up to the 2021 UN Climate Change Conference, COP26, being held in Glasgow in November, is our “last best chance” to urge world leaders to come together and commit to keeping climate change and its devastating impacts in check.

Description: Model fidelity and accuracy in process representations have been the crux of scientific hydrological modeling, creating a pressing need for a better linkage between the development of hydrological models and the growing number of data sources and measurement techniques. Improved representation of process dynamics in hydrological models can provide new insights into complex hydrological systems and point out less understood natural phenomena that need further investigation. This special issue includes contributions that offer potential solutions and strategies to improve and test the representation of hydrological processes. We have organized the special issue contributions into four topical categories: (a) Beyond streamflow, which looks into the power of complementary data sources in addition to traditionally used streamflow for process inference. (b) Challenge of subsurface hydrology, that reflects on lesser understood processes under the surface and their impact on the model structure. (c) Evaporation in hydrological modeling, linking ecological aspects to the hydrological functioning of the natural system. Finally, (d) top down vs. bottom up modeling approaches, relied upon for process representation analysis. The special issue and our reflection on the contributions present a snapshot of ongoing efforts for integrating new concepts, knowledge, and data in process representation in hydrological models.

Description: Remote imaging spectroscopy, also known as hyperspectral imaging, uses Radiative Transfer Models (RTMs) to predict the measured radiance spectrum for a specific surface and atmospheric state. Discrepancies between RTM assumptions and physical reality can cause systematic errors in surface property estimates. We present a statistical method to quantify these model errors without invoking ground reference data. Our approach exploits scene invariants — properties of the environment which are stable over space or time — to estimate RTM discrepancies. We describe techniques for discovering these features opportunistically in flight data. We then demonstrate data-driven methods that estimate the aggregate errors due to model discrepancies without having to explicitly identify the underlying physical mechanisms. The resulting distributions can improve posterior uncertainty predictions in operational retrievals.

Description: C–O–H–N–S-bearing fluids are known as one of the most challenging geochemical systems due to scarcity of available experimental data. H2S-rich fluid systems were recognized in a wide array of world-class mineral deposits and hydrocarbon reservoirs. Here we report on a nature of low-temperature (T ≥ −192 °C) phase transitions observed in natural CH4–H2S–CO2–N2–H2O fluid inclusions, which are modeled as closed thermodynamic systems and thus serve as natural micro-laboratories representative of the C–O–H–N–S system. For the first time, we document solid–solid H2S (α ↔ β ↔ γ) transitions, complex clathrates and structural transformations of solid state H2S in natural inclusion gas mixtures. The new data on Raman spectroscopic features and a complete sequence of phase transition temperatures in the gas mixtures contribute to scientific advancements in fluid geochemistry. Enhanced understanding of the phase equilibria in the C–O–H–N–S system is a prerequisite for conscientious estimation of P-T-V-X properties, necessary to model the geologic evolution of hydrocarbon and mineral systems. Our findings are a driver for the future research expeditions to extraterrestrial H2S-rich planetary systems owing to their low temperature environments.

Description: The Earth System Grid Federation (ESGF) provides access to the largest archive of model climate data world-wide. de-esgf-downloader provides a simple, programmatic interface to access/download the model climate data available in the ESGF archive. It supports parallel downloads of multiple datasets and dataset chunks, as well as caching of already downloaded datasets. It is developed at the GFZ German Research Centre for Geosciences (https://www.gfz-potsdam.de) and funded by the Initiative and Networking Fund of the Helmholtz Association through the Digital Earth project (https://www.digitalearth-hgf.de/). Link to Git Repository: https://git.geomar.de/digital-earth/de-climate-change/de-esgf-download

Description: de-similarity-backend-module wraps the floodsimilarity library and exposes it's functions to compute the similarity between multiple flood events via the DASF RPC messaging protocol. It is used by the Flood Similarity Workflow as part of the Digital Earth Flood Event Explorer. The de-similarity-backend-module is developed at the GFZ German Research Centre for Geosciences (https://www.gfz-potsdam.de) and funded by the Initiative and Networking Fund of the Helmholtz Association through the Digital Earth project (https://www.digitalearth-hgf.de/). The documentation for the functions and structures provided by the floodsimilarity library are available here: https://digital-earth.pages.geomar.de/floodsimilarity/

Description: The Digital Earth Controls and Indicators for Flood Impacts Backend Module cifi provides functions to access flood event data and identify relevant controls and useful indicators for the assessment of flood impacts (CIFI). This module contains a data acquisition pipeline to scrape available resources from the Copernicus Emergency Management Service (EMS) website and upload them to a workspace on a configured geoserver instance. The functions are exposed via the DASF RPC messaging protocol. It is used by the Socio-Economic Flood Impacts Workflow as part of the Digital Earth Flood Event Explorer. cifi is developed at the GFZ German Research Centre for Geosciences (https://www.gfz-potsdam.de) and funded by the Initiative and Networking Fund of the Helmholtz Association through the Digital Earth project (https://www.digitalearth-hgf.de/).

Description: We provide a single file (exodus II format) that contains all results of the modeling efforts of the associated paper. This encompasses all structural information as well as the pore pressure, temperature, and fluid velocity distribution through time. We also supply all files necessary to rerun the simulation, resulting in the aforementioned output file. The model area covers a rectangular area around the Central European Basin System (Maystrenko et al., 2020). The data publication is compeiment to Frick et al., (2021). The file published here is based on the structural model after Maystrenko et al., (2020) which resolves 16 geological units. More details about the structure and how it was derived can be found in Maystrenko et al., (2020). The file presented contains information on the regional variation of the pore pressure, temperature and fluid velocity of the model area in 3D. This information is presented for 364 time steps starting from 43,000 years before present and ending at 310000 years after present.

Description: This study presents an enhancement to the Global Navigation Satellite Systems (GNSS) by integrating low Earth orbiters (LEOs) to a joint precise orbit determination (POD) processing. The Global Position System (GPS) operated by the United States is studied as a representative of all GNSS. The LEOs equipped with GNSS receivers supplement the receivers of the ground stations, especially for regions with a limited number of employed stations, which can be caused by various reasons. Due to the altitude and high velocity of LEOs, they not only contribute with additional observations, but also with a rapidly-changing observation geometry. Moreover, space-based observations have additional advantages over ground-based observations, e.g., signals are received without the impact of the troposphere. LEOs not only act as kinematic stations for GNSS satellites, but also bring additional orbit dynamics to the integrated system. The constraints caused by these orbit dynamics have an important impact on the determination of the orbits of the GNSS satellites and other parameters beyond that. In this thesis, the following topics are presented: 1) Background information and the basic principles related to the POD of GNSS satellites and LEOs, 2) the separated POD of GNSS satellites and LEOs, 3) the integrated POD, 4) the determination of the antenna phase center offsets (PCOs) of the GPS satellites and other geodetic parameters in the integrated POD. The orbit modeling and processing configuration used in this study for GNSS satellites and LEOs are verified to be compatible with state-of-the-art studies by the separated POD. The orbits of the GNSS satellites and LEOs reach an accuracy of a few centimeters and are comparable with the state-of-art studies. A more efficient outlier detection method has been developed to improve the position determined by using pseudo-range observations. In the study about the enhancement of the GPS orbits by integrating LEOs, a 26-station ground network in a global and sparse distribution is supplemented by different subsets of seven LEOs including GRACE-A/B, OSTM/Jason-2, Jason-3 and, Swarm-A/B/C. A 34% improvement of the GPS orbit in 1D-mean RMS (from 37.5 mm to 23.9 mm) is achieved by including the seven LEOs. Both the number of space-based observations and the LEOs' orbital geometry affect the GPS orbits where the orbital geometry is shown to be more important. The estimated GPS PCOs are also improved by including LEOs. For the x- and y-components of the GPS PCOs, the formal error is reduced significantly due to the additional observations and expanded nadir angle coverage brought by the LEOs during the periods of large solar-elevation angle. The z-component of the GPS PCOs (z-PCO) are strongly correlated with the scale of the terrestrial reference frame. By introducing the orbit dynamics of the seven LEOs to the processing without applying a no-net-scale constraint, the correlation coefficients between the GPS z-PCOs and the scale are reduced from 0.85 to 0.30. Consequently, the GPS z-PCOs can be estimated independently from the a-priori scale and a purely GNSS-based scale can be determined as well. A system-specific -25.5 cm offset of the GPS z-PCOs relative to the values offered by the International GNSS Service (IGS) is computed based on the seven-LEO-integrated solution. Another approach based on Galileo also solves this problem. The GPS satellites, multi-GNSS stations, and Galileo satellites with ground calibrated PCOs are processed jointly to calibrate the GPS z-PCOs and simultaneously determine a Galileo-based scale simultaneously. Based on the comparison and cross-check, a good agreement is shown between the LEO-based and Galileo-based methods. There is a slight improvement in the geocenter when including three Swarm satellites to the processing with about 80 ground stations over a half year. Based on the analysis in theory and the results derived from real data, an obvious enhancement to various aspects of GNSS by the integrated processing with LEOs is shown. More LEOs equipped with GNSS receivers and carefully calibrated PCOs are expected for further missions or even the next generation of GNSS.

Description: In dieser Arbeit wird eine Verbesserung der globalen Satellitennavigationssysteme (GNSS) durch die Einbindung von Satelliten in niedrigen Erdumlaufbahnen (LEOs) in eine gemeinsame präzise Bahnbestimmung (POD) vorgestellt. Das von den Vereinigten Staaten betriebene Global Positioning System (GPS) wird stellvertretend für alle GNSS untersucht. Die mit GNSS-Empfängern ausgestatteten LEOs ergänzen die Empfänger der Bodenstationen, vor allem in Regionen, in denen aus verschiedenen Gründen nur wenige Stationen verfügbar sind. Aufgrund der Orbithöhe und schnellen Bewegung der LEOs tragen diese nicht nur mit zusätzlichen Beobachtungen bei, sondern auch mit einer sich schnell verändernden Beobachtungsgeometrie. Darüber hinaus haben weltraumgestützte Beobachtungen zusätzliche Vorteile gegenüber bodengestützten Beobachtungen, z. B. werden Signale ohne den Einfluss der Troposphäre empfangen. LEOs stellen nicht nur kinematische Stationen für die GNSS-Satelliten dar, sondern bringen auch eine zusätzliche Bahndynamik in das integrierte System ein. Die durch diese Bahndynamik gegebenen Beschränkungen sind sowohl für die Bahnbestimmung der GNSS Satelliten als auch für weitere Parameter äußerst relevant. In dieser Arbeit werden die folgenden Themen behandelt: 1) Hintergrundinformationen und Grundprinzipien der POD von GNSS-Satelliten und LEOs, 2) eine separate POD von GNSS-Satelliten und LEOs, 3) eine integrierte POD, 4) die Schätzung der Antennen-Phasenzentrumsversätze (PCOs) der GPS-Satelliten und anderer geodätischer Parameter in der integrierten POD. Die separaten PODs bestätigen, dass die in dieser Studie verwendete Bahnmodellierungs- und Prozessierungskonfiguration der GNSS-Satelliten und LEOs mit dem aktuellen Stand der Forschung kompatibel ist. Die Bahnen der GNSS-Satelliten und LEOs erreichen eine Genauigkeit von wenigen Zentimetern. Es wurde eine effizientere Methode zur Erkennung von Ausreißern entwickelt, um die mit Hilfe von Pseudo-Range-Beobachtungen ermittelte Position zu verbessern. Ein Bodennetz mit 26 global dünn verteilten Stationen wird verwendet, um die Verbesserung der GPS-Bahnen durch die Integration von verschiedenen Teilgruppen der sieben LEOs GRACE-A/B, OSTM/Jason-2, Jason-3 und Swarm-A/B/C zu untersuchen. Bei der Einbeziehung aller sieben LEOs ergibt sich eine Verbesserung des 1D RMS Mittelwertes der GPS-Orbits von 34 % (von 37,5 mm auf 23,9 mm). Sowohl die Anzahl der weltraumgestützten Beobachtungen als auch die Geometrie der Bahnen der LEOs beeinflussen die GPS-Bahnen, wobei die Orbitgeometrie sich als der wichtigere Faktor erweist. Die geschätzten GPS PCOs werden durch die Einbeziehung von LEOs ebenfalls verbessert. Der formale Fehler der x- und y-Komponenten der GPS PCOs wird durch die zusätzlichen Beobachtungen und die größere Abdeckung des Nadirwinkels, den die LEOs während Perioden eines großen Sonnenstandswinkels mit sich bringen, erheblich reduziert. Die z-Komponente der GPS PCOs (z-PCO) ist mit dem Maßstabsfaktor des terrestrischen Referenzrahmens stark korreliert. Durch die Berücksichtigung der Bahndynamik der sieben LEOs in der Prozessierung werden ohne Fixierung des Maßstabes (d.h. ohne eine No-Net-Scale Bedingung) die Korrelationskoeffizienten zwischen den GPS z-PCOs und dem Maßstabsfaktor von 0,85 auf 0,30 reduziert. Folglich können zum einen die GPS z-PCOs unabhängig von einem externen Maßstab geschätzt werden und zum anderen kann ein rein GNSS-basierter Maßstabsfaktor bestimmt werden. Mit der integrierten Lösung mit sieben LEOs ergibt sich ein systemspezifischer Versatz der GPS z-PCOs von -25,5 cm relativ zu den vom International GNSS Service (IGS) veröffentlichten Werten. Ein anderer Ansatz basierend auf Galileo löst dieses Problem ebenfalls. Die GPS Satelliten, Multi-GNSS Bodenstationen und Galileo Satelliten mit bodenkalibrierten PCOs werden gemeinsam prozessiert, um die GPS z-PCOs zu kalibrieren und gleichzeitig einen Galileo-basierten Maßstabsfaktor zu bestimmen. Ein Vergleich zur Überprüfung zeigt eine hohe Übereinstimmung der LEO- und Galileo-basierten Methoden. Die Einbeziehung von drei Swarm Satelliten in eine Prozessierung mit etwa 80 Bodenstationen über ein halbes Jahr hinweg zeigt eine leichte Verbesserung des Geozentrums. Auf der Grundlage der theoretischen Analyse und der aus realen Daten abgeleiteten Ergebnisse zeigt sich eine deutliche Verbesserung verschiedener Aspekte der GNSS durch die Integration von LEOs. Es ist zu erwarten, dass mehr LEOs, ausgestattet mit GNSS-Empfängern und sorgfältig kalibrierten PCOs, für künftige Missionen oder sogar die nächste GNSS Generation eingesetzt werden.

Description: Water reinjection into the formation is an indispensable operation in many energy engineering practices. This operation involves a complex hydromechanical (HM) coupling process and sometimes even causes unpredictable disasters, such as induced seismicity. It is acknowledged that the relative magnitude and direction of the principal stresses significantly influence the HM behaviors of rocks during injection. However, due to the limitations of current testing techniques, it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions, such as in triaxial extension stress states. To this end, a numerical study of HM changes in rocks during injection under different stress states is conducted. In this model, the saturated rock is first loaded to the target stress state under drainage conditions, and then the stress state is maintained and water is injected from the top to simulate the formation injection operation. Particular attention is given to the difference in HM changes under triaxial compression and extension stresses. This includes the differences in the pore pressure propagation, mean effective stress, volumetric strain, and stress-induced permeability. The numerical results demonstrate that the differential stress will significantly affect the HM behaviors of rocks, but the degree of influence is different under the two triaxial stress states. The HM changes caused by the triaxial compression stress states are generally greater than those of extension, but the differences decrease with increasing differential stress, indicating that the increase in the differential stress will weaken the impact of the stress state on the HM response. In addition, the shear failure p otential of fracture planes with various inclination angles is analyzed and summarized under different stress states. It is recommended that engineers could design suitable injection schemes according to different tectonic stress fields versus fault occurrence to reduce the risk of injection-induced seismicity.

Description: Special Issue: Abstracts of the International Symposium on Deep Earth Exploration and Practices, 1–5 Nov 2021, Nanjing, China

Description: We present Space-VLBI RadioAstron observations at 1.6 GHz and 4.8 GHz of the flat spectrum radio quasar 3C 273, with detections on baselines up to 4.5 and 3.3 Earth Diameters, respectively. Achieving the best angular resolution at 1.6 GHz to date, we have imaged limb-brightening in the jet, not previously detected in this source. In contrast, at 4.8 GHz, we detected emission from a central stream of plasma, with a spatial distribution complementary to the limb-brightened emission, indicating an origin in the spine of the jet. While a stratification across the jet width in the flow density, internal energy, magnetic field, or bulk flow velocity are usually invoked to explain the limb-brightening, the different jet structure detected at the two frequencies probably requires a stratification in the emitting electron energy distribution. Future dedicated numerical simulations will allow the determination of which combination of physical parameters are needed to reproduce the spine-sheath structure observed by Space-VLBI with RadioAstron in 3C 273.

Description: The rheology of the upper mantle impacts a variety of geodynamic processes, including postseismic deformation following great earthquakes and post-glacial rebound. The deformation of upper mantle rocks is controlled by the rheology of olivine, the most abundant upper mantle mineral. The mechanical properties of olivine at steady state are well constrained. However, the physical mechanism underlying transient creep, an evolutionary, hardening phase converging to steady state asymptotically, is still poorly understood. Here, we constrain a constitutive framework that captures transient creep and steady state creep consistently using the mechanical data from laboratory experiments on natural dunites containing at least 94% olivine under both hydrous and anhydrous conditions. The constitutive framework represents a Burgers assembly with a thermally activated nonlinear stress-versus-strain-rate relationship for the dashpots. Work hardening is obtained by the evolution of a state variable that represents internal stress. We determine the flow law parameters for dunites using a Markov chain Monte Carlo method. We find the activation energy 430±20 and 250±10 kJ/mol for dry and wet conditions, respectively, and the stress exponent 2.0±0.1 for both the dry and wet cases for transient creep, consistently lower than those of steady-state creep, suggesting a separate physical mechanism. For wet dunites in the grain-boundary sliding regime, the grain-size dependence is similar for transient creep and steady-state creep. The lower activation energy of transient creep could be due to a higher jog density of the corresponding soft-slip system. More experimental data are required to estimate the activation volume and water content exponent of transient creep. The constitutive relation used and its associated flow law parameters provide useful constraints for geodynamics applications.

Description: Dynamic earthquake rupture causes mass redistribution around the fault, and the emitted propagating seismic waves are accompanied by bulk density perturbations. Both processes cause transient gravity changes prior to the arrival of P-waves. Such pre-P gravity signals have been detected in previous studies of several large earthquakes. However, the detections were limited to the vertical component of the signal owing to the high noise level in the horizontal records. In this study, we analyzed dense tiltmeter array data in Japan to search for the horizontal components of the signal from the 2011 Mw 9.1 Tohoku-Oki earthquake. Based on the synthetic waveforms computed for a realistic Earth model, we stacked the horizontal records and identified a signal that evidently exceeded the noise level. We further performed a waveform inversion analysis to estimate the source parameters. The horizontal tiltmeter data, combined with the vertical component of the broadband seismometer array data, yielded a constraint on the dip angle and magnitude of the earthquake in the ranges of 11.5°–15.3° and 8.75°–8.92°, respectively. Our results indicate that the analysis of the three components of the pre-P gravity signal avoids the intrinsic trade-off problem between the dip angle and seismic moment in determining the source mechanism of shallow earthquakes. Pre-P gravity signals open a new observation window for earthquake source studies.

Description: Large-scale flood risk assessments are crucial for decision making, especially with respect to new flood defense schemes, adaptation planning and estimating insurance premiums. We apply the process-based Regional Flood Model to simulate a 5000-year flood event catalogue for all major catchments in Germany and derive risk curves based on the losses per economic sector. The RFM uses a continuous process simulation including a multisite, multivariate weather generator, a hydrological model considering heterogeneous catchment processes, a coupled 1D–2D hydrodynamic model considering dike overtopping and hinterland storage, spatially explicit sector-wise exposure data and empirical multi-variable loss models calibrated for Germany. For all components, uncertainties in the data and models are estimated. We estimate the median Expected Annual Damage (EAD) and Value At Risk at 99.5% confidence for Germany to be €0.529 bn and €8.865 bn, respectively. The commercial sector dominates by making about 60% of the total risk, followed by the residential sector. The agriculture sector gets affected by small return period floods and only contributes to less than 3% to the total risk. The overall EAD is comparable to other large-scale estimates. However, the estimation of losses for specific return periods is substantially improved. The spatial consistency of the risk estimates avoids the large overestimation of losses for rare events that is common in other large-scale assessments with homogeneous return periods. Thus, the process-based, spatially consistent flood risk assessment by RFM is an important step forward and will serve as a benchmark for future German-wide flood risk assessments.

Description: Subduction initiation induced by a hot and buoyant mantle plume head is unique among proposed subduction initiation mechanisms because it does not require pre-existing weak zones or other forces for lithospheric collapse. Since recognition of the first evidence of subduction nucleation induced by a mantle plume in the Late Cretaceous Caribbean realm, the number of studies focusing on other natural examples has grown. Here, we review numerical and physical modeling and geological-geochemical studies which have been carried out thus far to investigate onset of a new subduction zone caused by impingement of a mantle plume head. As geological-geochemical data suggests that plume-lithosphere interactions have long been important - spanning from the Archean to the present - modeling studies provide valuable information on the spatial and temporal variations in lithospheric deformation induced by these interactions. Numerical and physical modeling studies, ranging from regional to global scales, illustrate the key role of plume buoyancy, lithospheric strength and magmatic weakening above the plume head on plume-lithosphere interactions. Lithospheric/crustal heterogeneities, pre-existing lithospheric weak zones and external compressional/extensional forces may also change the deformation regime caused by plume-lithosphere interaction.

Description: The need for explicitly considering equity in climate change adaptation planning is increasingly being recognized. However, evaluations of adaptation often adopt an aggregated perspective, while disaggregation of results is important to learn about who benefits when and where. A typical example is adaptation of rice agriculture in the Vietnam Mekong Delta (VMD). Efforts focused on flood protection have mainly benefitted large-scale farmers while harming small-scale farmers. To investigate the distributional consequences of adaptation policies in the VMD, we assess both aggregate total output and equity indicators, as well as disaggregated impacts in terms of district-level farming profitability. Doing so requires an adequate representation of the multisectoral dynamics between the human and biophysical systems which influence farming profitability. We develop a spatially explicit integrated assessment model that couples inundation, sedimentation, soil fertility and nutrient dynamics, and behavioral land-use change and farming profitability calculation. We find that inter-district inequality responds in a non-linear way to climatic and socio-economic changes and choices of adaptation policies. The patterns of who wins and who loses could change substantially when a different policy is implemented or if a slightly different uncertain future materializes. We also find that there is no simple ranking of alternative adaptation policies, so one should make trade-offs based on agreed preferences. Accounting for equity implies exploring the distribution of outcomes over different groups over a range of uncertain futures. Only by accounting for multisectoral dynamics can planners anticipate the equity consequences of adaptation and prepare additional measures to aid the worse-off actors.

Description: Pluvial floods in urban areas are caused by local, fast storm events with very high rainfall rates, which lead to inundation of streets and buildings before the storm water reaches a watercourse. An increase in frequency and intensity of heavy rainfall events and an ongoing urbanization may further increase the risk of pluvial flooding in many urban areas. Currently, warnings for pluvial floods are mostly limited to information on rainfall intensities and durations over larger areas, which is often not detailed enough to effectively protect people and goods. We present a proof‐of‐concept for an impact‐based forecasting system for pluvial floods. Using a model chain consisting of a rainfall forecast, an inundation, a contaminant transport and a damage model, we are able to provide predictions for the expected rainfall, the inundated areas, spreading of potential contamination and the expected damage to residential buildings. We use a neural network‐based inundation model, which significantly reduces the computation time of the model chain. To demonstrate the feasibility, we perform a hindcast of a recent pluvial flood event in an urban area in Germany. The required spatio‐temporal accuracy of rainfall forecasts is still a major challenge, but our results show that reliable impact‐based warnings can be forecasts are available up to 5 min before the peak of an extreme rainfall event. Based on our results, we discuss how the outputs of the impact‐based forecast could be used to disseminate impact‐based early warnings.

Description: We analyze sporadic E (ES) occurrence rates (OR) obtained from ionospheric radio occultation measurements by the FORMOSAT-3/COSMIC constellation. Maximum OR are seen at 95 - 105 km altitude at lower midlatitudes. Midlatitude ES are mainly due to wind shear in the presence of tides, and the strongest signals are a migrating diurnal and semidiurnal com- ponent. Especially at high latitudes of the southern hemisphere, nonmigrating components such as a diurnal westward wave 2 and a semidiurnal westward wave 1 are also visible. Near the equator, a strong diurnal eastward wavenumber 3 component and a semidiurnal eastward wavenumber 2 component is found in summer and autumn. Terdiurnal and quarterdiurnal components are weaker than the diurnal and semidiurnal ones

Description: For a long time， with the continuous expansion of the oil and gas genesis theory and the increasing global demand for clean energy， hydrogen， as an important link connecting the theory of inorganic and organic hydrocarbon generation， as well as a promising clean energy， has gradually attracted widespread academic attention. The genesis of hydrogen in natural gas is relatively complex and diverse. According to its reaction mechanism， it can be divided into two categories： inorganic and organic. Inorganic genesis is mainly earth degassing， water rock reaction and water radiation decomposition， while organic genesis is dominated by biological action and organic matter pyrolysis. At present， hydrogen isotope and geochemical characteristics of associated gases are mainly used to identify the origin of hydrogen. However， due to the complex and diverse sources of hydrogen and its active chemical properties， it is still unable to identify the origin of hydrogen systematically and accurately. Due to the extensive genesis of hydrogen， natural gas with different hydrogen concentrations has been found in different geological conditions around the world， and the hydrogen content varies greatly （0.1%-99%）. Hydrogen can participate in hydrocarbon generation in Fischer Tropsch synthesis as a reducing agent， and also can be used as a hydrogen source to improve the hydrocarbon yield during the thermal evolution of organic matter. Therefore， the existence of hydrogen may extend the lower limit of deep gas exploration and development. Based on the systematic summary of the genetic mechanism and distribution of hydrogen， this paper discusses the energy significance of hydrogen in natural gas， and provides a reference for the future research on hydrogen rich natural gas resources.

Description: To solve the problem that integer ambiguity between middle-range reference stations in BDS is difficult to be fixed correctly due to the influence of ionospheric delay error and tropospheric delay error, an algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations was proposed. Firstly, the frequency observations of B2 and B3 were used to determine B2-B3 extra-wide-lane integer ambiguity. Then, B1-B3 wide-lane integer ambiguity was solved by using the closer characteristic of ionospheric delay error between B2-B3 extra-wide-lane and B1-B3 wide-lane combination observation, and B1-B2 wide-lane integer ambiguity can be fixed according to the linear relationship of triple-frequency integer ambiguity. Furthermore, B1-B3 and B1-B2 ionosphere-free combination observation and the decomposable characteristic of the corresponding integer ambiguity were used to estimate narrow-lane integer ambiguity and relative zenith tropospheric delay error, and then narrow-lane integer ambiguity can be finally fixed by search mode. This algorithm is tested by the measured triple-frequency data of BDS CORS network. The results show that triple-frequency carrier phase integer ambiguity between middle-range BDS reference stations can be fixed accurately and effectively with the method. © 2021, Editorial Board of Journal of CUMT. All right reserved. Search Sources Lists SciVal ALBERT Telegrafenberg Holdings (Opens new window) Alerts Document details - The algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations Back to results Previous 3of20 Next SFX Get it!(opens in a new window)|Entitled full text| Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and TechnologyVolume 50, Issue 2, Pages 396 - 403March 2021 Document type Article Source type Journal ISSN 10001964 The algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations[BDS中距离参考站三频整周模糊度确定方法] a , a, a, b, a To solve the problem that integer ambiguity between middle-range reference stations in BDS is difficult to be fixed correctly due to the influence of ionospheric delay error and tropospheric delay error, an algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations was proposed. Firstly, the frequency observations of B2 and B3 were used to determine B2-B3 extra-wide-lane integer ambiguity. Then, B1-B3 wide-lane integer ambiguity was solved by using the closer characteristic of ionospheric delay error between B2-B3 extra-wide-lane and B1-B3 wide-lane combination observation, and B1-B2 wide-lane integer ambiguity can be fixed according to the linear relationship of triple-frequency integer ambiguity. Furthermore, B1-B3 and B1-B2 ionosphere-free combination observation and the decomposable characteristic of the corresponding integer ambiguity were used to estimate narrow-lane integer ambiguity and relative zenith tropospheric delay error, and then narrow-lane integer ambiguity can be finally fixed by search mode. This algorithm is tested by the measured triple-frequency data of BDS CORS network. The results show that triple-frequency carrier phase integer ambiguity between middle-range BDS reference stations can be fixed accurately and effectively with the method. © 2021, Editorial Board of Journal of CUMT. All right reserved.

Description: The underwater positioning of marine acoustic datum is mainly based on the principle of spatial distance intersection positioning. As the limitation of the observation structure, the observation error is easy to accumulate in the vertical direction. If the accurate depth of marine acoustic datum can be obtained and used for depth constrained positioning, it will help to further improve the positioning accuracy of marine acoustic datum. The depth gauge based on the principle of pressure measurement has been widely concerned due to the advantage of autonomous depth measurement. However, the effect of pressure-depth conversion on the positioning error of marine acoustic datum under depth constraint has not drawn enough scholarly attention. This paper focuses on the evaluation of the pressure-depth conversion accuracy of different seawater physical models and conducts an experimental analysis based on Argo buoy data. The results of the experiment show that the TEOS-10 model has the highest conversion accuracy, and using accurate profile information of temperature, salinity, and pressure parameters to correct the depth data is helpful to improve the accuracy of marine acoustic datum positioning.

Description: The Association of Polar Early Career Scientists (APECS) is an international, interdisciplinary organisation for all early-career researchers, educators, and professionals with interests in polar and alpine regions. APECS international is governed by an executive committee and the APECS Council. The German National Committee organises APECS activities at the national level in Germany and is overseen by a directing board. We welcome members who have connections to the German polar, permafrost, alpine, and cryosphere research communities. Following the relocation of the APECS International Directorate to the Alfred Wegener Institute (AWI) campus in Potsdam in 2017, the links between APECS international and APECS Germany have never been stronger. It is with this momentum that we inaugurate our first column in our new, dedicated Polarforschung pages. Our first edition will introduce you to two former APECS Germany chairs, who share their perspectives on APECS and their experiences working as polar early-career researchers.

Description: Underground exploitation of georesources can be highly correlated with induced seismic activity. In order to reduce the risk and improve the mining operations safety, the mining activity is monitored by a dedicated seismic network. Moment tensor inversion is a powerful method to investigate the rupture process of earthquakes in mines, providing information on the geometry of the earthquake source and the moment release. Different approaches have been proposed to estimate the source mechanisms, with some advantages and limitations. One of the simplest and most used methods rely on the fit of the polarity and amplitude of first P wave onsets. More advanced techniques fit the full waveforms and their spectra. Here, we test and compare moment tensor and focal mechanism estimations for both inversion techniques. In order to assess the inversion resolution, we built realistic synthetic data, accounting for real seismic noise conditions and network geometry for the Rudna copper mine, SW Poland. The Rudna mine pertains to the Legnica-Glógow Copper District, where thousands of mining induced earthquakes are detected yearly, representing a serious hazard for miners and mining infrastructures. We simulate a range of different processes and locations, considering pure double couple, deviatoric and full moment tensors with different magnitudes and located in different mining panels. Results show that the P-wave first onset inversion is very sensitive to the geometry of the seismic network, which is limited by the existing underground infrastructure. On the other hand, the quality of the moment tensor solutions for the full waveform inversion is mainly determined by the strength of mining tremor and the signal-to-noize ratio. We discuss the performance of both inversion techniques and provide recommendations toward a reliable moment tensor analysis in mines.

Description: Light pollution is an environmental stressor of global extent that is growing exponentially in area and intensity. Artificial skyglow, a form of light pollution with large range, is hypothesized to have environmental impact at ecosystem level. However, testing the impact of skyglow at large scales and in a controlled fashion under in situ conditions has remained elusive so far. Here we present the first experimental setup to mimic skyglow at ecosystem level outdoors in an aquatic environment. Spatially diffuse and homogeneous surface illumination that is adjustable between 0.01 and 10 lx, resembling rural to urban skyglow levels, was achieved with white light-emitting diodes at a large-scale lake enclosure facility. The illumination system was enabled by optical modeling with Monte-Carlo raytracing and validated by measurements. Our method can be adapted to other outdoor and indoor skyglow experiments, urgently needed to understand the impact of skyglow on ecosystems.

Description: Artificial light at night (ALAN) is closely associated with modern societies and is rapidly increasing worldwide. A dynamically growing body of literature shows that ALAN poses a serious threat to all levels of biodiversity—from genes to ecosystems. Many “unknowns” remain to be addressed however, before we fully understand the impact of ALAN on biodiversity and can design effective mitigation measures. Here, we distilled the findings of a workshop on the effects of ALAN on biodiversity at the first World Biodiversity Forum in Davos attended by several major research groups in the field from across the globe. We argue that 11 pressing research questions have to be answered to find ways to reduce the impact of ALAN on biodiversity. The questions address fundamental knowledge gaps, ranging from basic challenges on how to standardize light measurements, through the multi-level impacts on biodiversity, to opportunities and challenges for more sustainable use.

Description: The detection of transient events related to slow earthquakes in GNSS positional time series is key to understanding seismogenic processes in subduction zones. Here, we present a novel Principal and Independent Components Correlation Analysis (PICCA) method that allows for the temporal and spatial detection of transient signals. The PICCA is based on an optimal combination of the principal (PCA) and independent component analysis (ICA) of positional time series of a GNSS network. We assume that the transient signal is mostly contained in one of the principal or independent components. To detect the transient, we applied a method where correlations between sliding windows of each PCA/ICA component and each time series are calculated, obtaining the stations affected by the slow slip event and the onset time from the resulting correlation peaks. We first tested and calibrated the method using synthetic signals from slow earthquakes of different magnitudes and durations and modelled their effect in the network of GNSS stations in Chile. Then, we analyzed three transient events related to slow earthquakes recorded in Chile, in the areas of Iquique, Copiapó, and Valparaíso. For synthetic data, a 150 days event was detected using the PCA-based method, while a 3 days event was detected using the ICA-based method. For the real data, a long-term transient was detected by PCA, while a 16 days transient was detected by ICA. It is concluded that simultaneous use of both signal separation methods (PICCA) is more effective when searching for transient events. The PCA method is more useful for long-term events, while the ICA method is better suited to recognize events of short duration. PICCA is a promising tool to detect transients of different characteristics in GNSS time series, which will be used in a next stage to generate a catalog of SSEs in Chile.

Description: Hydrothermal regions experience various phenomena, including ground deformation and, in the case of calderas, interaction between deep magmatic processes and shallow aquifers. The present work considers a source model consisting of a disk-shaped thermo-poro-elastic inclusion subject to a sudden change of temperature and pore pressure, embedded in a homogeneous poro-elastic halfspace. We compare semi-analytical solutions for surface displacement with results from four other source models. The displacement components are similar to those of a spherical point-like source for a certain choice of geometric parameters, while they differ from the other models. On the basis of this comparison, we interpret the results of inversions on ground deformation data of the 1982–1984 unrest episode at Campi Flegrei caldera, Italy, where the thermo-poro-elastic source provides the best fit.

Description: The workflow for estimating the temperature in agricultural fields from multiple sensors needs to be optimized upon testing each type of sensor’s actual user performance. In this sense, readily available miniaturized UAV-based thermal infrared (TIR) cameras can be combined with proximal sensors in measuring the surface temperature. Before the two types of cameras can be operationally used in the field, laboratory experiments are needed to fully understand their capabilities and all the influencing factors. We present the measurement results of laboratory experiments of UAV-borne WIRIS 2nd GEN and handheld FLIR E8-XT cameras. For these uncooled sensors, it took 30 to 60 min for the measured signal to stabilize and the sensor temperature drifted continuously. The drifting sensor temperature was strongly correlated to the measured signal. Specifically for WIRIS, the automated non-uniformity correction (NUC) contributed to extra uncertainty in measurements. Another problem was the temperature measurement dependency on various ambient environmental parameters. An increase in the measuring distance resulted in the underestimation of surface temperature, though the degree of change may also come from reflected radiation from neighboring objects, water vapor absorption, and the object size in the field of view (FOV). Wind and radiation tests suggested that these factors can contribute to the uncertainty of several Celsius degrees in measured results. Based on these indoor experiment results, we provide a list of suggestions on the potential practices for deriving accurate temperature data from radiometric miniaturized TIR cameras in actual field practices for (agro-)environmental research.

Description: This paper describes the concept of an innovative, interdisciplinary, user-oriented earthquake warning and rapid response system coupled with a structural health monitoring system (SHM), capable to detect structural damages in real time. The novel system is based on interconnected decentralized seismic and structural health monitoring sensors. It is developed and will be exemplarily applied on critical infrastructures in Lower Rhine Region, in particular on a road bridge and within a chemical industrial facility. A communication network is responsible to exchange information between sensors and forward warnings and status reports about infrastructures’ health condition to the concerned recipients (e.g., facility operators, local authorities). Safety measures such as emergency shutdowns are activated to mitigate structural damages and damage propagation. Local monitoring systems of the infrastructures are integrated in BIM models. The visualization of sensor data and the graphic representation of the detected damages provide spatial content to sensors data and serve as a useful and effective tool for the decision-making processes after an earthquake in the region under consideration.

Description: The equatorial electrojet (EEJ) represents a ribbon of intense electric current flowing in the ionospheric E region on the dayside along the dip-equator. The primary reason for the high current density is the geometry of the geomagnetic field with its horizontal field lines at these latitudes. This enables a greatly enhanced electrical conductivity in the ionospheric E layer over a latitudinal width of about 600 km. Any low-latitude electric field in that region will give rise to significant currents in that channel. In this chapter we will first present some historical observations that lead to the discovery and early characterization of the EEJ. In those years, most of the studies were based on magnetic signatures observed on ground. Significant progress in understanding the EEJ could be made when measurements from low-Earth orbiting satellites became routinely available. Subsequently, we describe the electrodynamics that governs the EEJ properties. These can be used for predicting important EEJ features. Besides the physics-based models, an empirical model based on a large observational data set is presented. From this model, the main climatological characteristics of the EEJ can be deduced, such as diurnal, annual and longitudinal variations, as well as dependencies on solar and magnetic activities. The tidal modulation plays an important role for the temporal and spatial variation of the EEJ intensity. We describe both the influences of solar and lunar tides. At times the commonly eastward EEJ current reverses to westward. Here the most important processes are described that cause the counter equatorial electrojet. In the end, the prime features of the EEJ are summarized and remaining open issues are presented.