ALBERT

Description: We provide seismological data from a huddle test in Fürstenfeldbruck in August 2019 that was realized by University of Potsdam (PI: Eva Eibl) in collaboration with BGR (PI: Stefanie Donner) and LMU (PI: Felix Bernauer). 5 rotational sensors (blueSeis-3A) and 3 seismometers (Trillium Horizon 120s Nanometrics) were installed on a decoupled basement in a building of the Geophysical Observatory Fürstenfeldbruck. The seismometers were isolated with black foam rubber and white cotton. We recorded passive seismological data for one week and recorded noise, coherent noise sources and the August 29, 2019 ML 3.4 Dettingen earthquake. The aim of the seismic experiment is to compare the performance of rotational sensors and seismometers with respect to different coherent and incoherent noise sources. The noise level, spectral content of the coherent noise and back azimuth of the Dettingen earthquake was further investigated for all sensors using correlation, coherence analysis and probabilistic power spectral densities in Izgi et al. (2021). Waveform data are available from the GEOFON data centre, under network code X3 under CC-BY 4.0 license.

Description: poster

Description: The bioavailability of molecular oxygen is considered a driving force for the evolution of phenotypic complexity, yet the geological history of biological oxygen production remains poorly constrained. Fossilized 2-methylhopanoids (2-methylhopanes) were once considered diagnostic for the presence of cyanobacteria and oxygenic photosynthesis. However, the subsequent discovery of C-2 hopanoid methyltransferase (hpnP) in non-cyanobacterial species questioned the utility of 2-methylhopanes as cyanobacterial biomarkers. Here we re-examined the distribution of HpnP in the bacterial domain and the evolutionary history of HpnP. Our results suggest that HpnP did not originate within α-proteobacteria but rather was already present in the common ancestor of cyanobacteria, contrary to previous inferences. Molecular clock analyses further suggest that the emergence of HpnP in cyanobacteria substantially predates the emergence of HpnP in α-proteobacteria and 2-methylhopanes in rocks deposited prior to 1.2 Ga are inferred to be derived uniquely from cyanobacteria. Our results imply that 2-methylhopanes can theoretically allow us to trace the rise of oxygenic photosynthesis even prior to the GOE if suitable sedimentary sequences or preservation windows should be found in the future.

Description: This dataset is composed of three-season simulated EnMAP mosaics for the Lake Tahoe region, USA. HyspIRI Airborne Campaign AVIRIS imagery from spring, summer and fall formed the basis for simulating EnMAP data with 30 m spatial resolution and 195 spectral bands ranging from 420 to 2450 nm. The mosaics are provided as Analysis-Ready-Datasets (tiled surface reflectance products) to be used for regional-scale and multi-season hyperspectral image analysis of California’s diverse ecoregions. The dataset primarily intends to support the development of processing algorithms and to demonstrate spaceborne hyperspectral data capabilities during the pre-launch activities of the forthcoming EnMAP mission. This dataset was processed in line with companion simulated EnMAP mosaics for the San Francisco Bay Area and for the Santa Barbara region.

Description: This dataset is composed of three-season simulated EnMAP mosaics for the Lake Tahoe region, USA. HyspIRI Airborne Campaign AVIRIS imagery from spring, summer and fall formed the basis for simulating EnMAP data with 30 m spatial resolution and 195 spectral bands ranging from 420 to 2450 nm. The mosaics are provided as Analysis-Ready-Datasets (tiled surface reflectance products) to be used for regional-scale and multi-season hyperspectral image analysis of California’s diverse ecoregions. The dataset primarily intends to support the development of processing algorithms and to demonstrate spaceborne hyperspectral data capabilities during the pre-launch activities of the forthcoming EnMAP mission. This dataset was processed in line with companion simulated EnMAP mosaics for the San Francisco Bay Area (Cooper et al. 2020a) and for the Santa Barbara region (Okujeni et al. 2021a).

Description: This dataset is composed of three-season simulated EnMAP mosaics for the Santa Barbara region, USA. HyspIRI Airborne Campaign AVIRIS imagery from spring, summer and fall formed the basis for simulating EnMAP data with 30 m spatial resolution and 195 spectral bands ranging from 420 to 2450 nm. The mosaics are provided as Analysis-Ready-Datasets (tiled surface reflectance products) to be used for regional-scale and multi-season hyperspectral image analysis of California’s diverse ecoregions. The dataset primarily intends to support the development of processing algorithms and to demonstrate spaceborne hyperspectral data capabilities during the pre-launch activities of the forthcoming EnMAP mission. This dataset was processed in line with companion simulated EnMAP mosaics for the San Francisco Bay Area (Cooper et al. 2020a) and for the Lake Tahoe region (Okujeni et al. 2021a).

Description: This dataset is composed of three-season simulated EnMAP mosaics for the Santa Barbara region, USA. HyspIRI Airborne Campaign AVIRIS imagery from spring, summer and fall formed the basis for simulating EnMAP data with 30 m spatial resolution and 195 spectral bands ranging from 420 to 2450 nm. The mosaics are provided as Analysis-Ready-Datasets (tiled surface reflectance products) to be used for regional-scale and multi-season hyperspectral image analysis of California’s diverse ecoregions. The dataset primarily intends to support the development of processing algorithms and to demonstrate spaceborne hyperspectral data capabilities during the pre-launch activities of the forthcoming EnMAP mission. This dataset was processed in line with companion simulated EnMAP mosaics for the San Francisco Bay Area and for the Lake Tahoe region.

Description: The analysis of the Coulomb stress changes has become an important tool for seismic hazard evaluation because such stress changes may trigger or delay next earthquakes. Processes that can cause significant Coulomb stress changes include coseismic slip, earthquake-induced poroelastic effects as well as transient postseismic processes such as viscoelastic relaxation. In this study, we investigate the spatial and temporal evolution of pore fluid pressure changes and fluid flow during the seismic cycle, their dependency on the permeability in the crust and the interaction with postseismic viscoelastic relaxation. To achieve this, we use 2D finite-element models for intra-continental normal and thrust faults, which include coseismic slip, poroelastic effects, postseismic viscoelastic relaxation and interseismic stress accumulation. In different experiments, we vary (1) the permeability of the upper and lower crust while keeping the viscosity structure constant and (2) the viscosity of the lower crust and lithospheric mantle, while we keep the permeabilities constant. (1) The modelling results show that the highest changes in pore fluid pressure during and after the earthquake occur within a distance of ~ 1 km around the lower fault tip at the transition between upper and lower crust. The evolution of pore pressure and fluid flow depends primarily on the permeability in the upper crust. With decreasing permeability, the possibility of the pore fluids to flow decreases and thus, in the postseismic phase, the duration of the poroelastic relaxation increases, from a few days to several years, until the pore pressure reaches the initial pressure of the preseismic phase. In contrast, the influence of variations of the permeability in the lower crust on the pore pressure changes is negligible. For high upper-crustal permeabilities, postseismic vertical velocities are high and decreases rapidly with time, from around 120 mm/a after the first year by two orders of magnitude after 10 years, whereas for low permeabilities they remain consistently low over the years after the earthquake. (2) Models with low viscosity of the lower crust show that the timescales of poroelastic effects and viscoelastic relaxation overlap and affect the postseismic velocity already in the early postseismic phase and that both processes decay within a few years after the earthquake. For higher viscosities, the velocity is initially dominated by pore pressure changes during the first few years, whereas viscoelastic relaxation lasts for decades. Both processes also show differences in their spatial scale. Poroelastic effects occur within a few kilometers around the fault, whereas viscoelastic relaxation acts on tens to hundreds of kilometers. As both processes can cause Coulomb stress changes on faults in the vicinity of the earthquake source fault, it is important to understand the spatial and temporal evolution, the effects on the individual faults and the interaction of both processes during the earthquake cycle. Future work will therefore include the calculation and examination of Coulomb stress changes on intra-continental normal and thrust faults using 3D models that include poroelastic effects and viscoelastic relaxation.

Description: The lunar mascon basins are characterized by high gravity anomalies and thin crust. Study of the density structure beneath the mascon basins can help to understand the origin of these gravity anomalies and infer their formation and evolution. We propose an efficient forward gravity method based on the 3-D Gauss-Legendre quadrature (GLQ) and Fast Fourier Transforms combined with the adaptive discretization strategy to ensure high accuracy. The numerical example demonstrates that computational efficiency is increased by about three orders of magnitude compared to the traditional 3D GLQ method. We employ this forward method in a 3-D inversion of the gravity data derived from the lunar gravity model GL1500E. The inverted results show prominent high-density structures (namely, mascons) representing significant mantle uplift and thinned crust beneath most impact basins. Marked low-density rings surround the mascons. Most of the corresponding low-density anomalies extend from the near-surface to the Moho, indicating a thick, low-density crust. Our density model is consistent with the formation processes of mascons that an impact causes collapse of the transient crater and then the shocked mantle drives mantle flow. The low-density rings surrounding the mascons may stem from the crust thickening following an impact and extensive fracturing of the crustal column.

Description: The Alpine Fault zone in New Zealand marks a major transpressional plate boundary that is late in its typical earthquake cycle. Understanding the subsurface structures is crucial to understand the tectonic processes taking place. A unique seismic survey including 2D lines, a 3D array, and borehole recordings, has been performed in the Whataroa Valley and provides new insights into the Alpine Fault zone down to ∼2 km depth at the location of the Deep Fault Drilling Project (DFDP)‐2 drill site. Seismic images are obtained by focusing prestack depth migration approaches. Despite the challenging conditions for seismic imaging within a sediment filled glacial valley and steeply dipping valley flanks, several structures related to the valley itself as well as the tectonic fault system are imaged. A set of several reflectors dipping 40°–56° to the southeast are identified in a ∼600 m wide zone that is interpreted to be the minimum extent of the damage zone. Different approaches image one distinct reflector dipping at ∼40°, which is interpreted to be the main Alpine Fault reflector located only ∼100 m beneath the maximum drilled depth of the DFDP‐2B borehole. At shallower depths (z 〈 0.5 km), additional reflectors are identified as fault segments with generally steeper dips up to 56°. Additionally, a glacially over‐deepened trough with nearly horizontally layered sediments and a major fault (z 〈 0.5 km) are identified 0.5–1 km south of the DFDP‐2B borehole. Thus, a complex structural environment is seismically imaged and shows the complexity of the Alpine Fault at Whataroa.

Description: Plain Language Summary: The Alpine Fault in New Zealand is a major plate boundary, where a large earthquake will likely occur in the near future. Thus, it is important to understanding the detailed processes of how and where such an earthquake occurs. Many scientists are involved in this work, particularly in the attempt of drilling through the fault zone with a ∼900 m deep borehole. We analyzed new seismic data from this area using sensors in the borehole and at the surface to record small ground movements caused by a vibrating surface source causing waves that travel through the ground. From these data, we obtained a detailed image of the structures in the subsurface, for the first time in 3D, by applying advanced analysis methods. Hence, we can better understand the shape of the glacial valley and of the fault zone, that is, the local structures of the continental plate boundary. We interpret at least 600 m wide zone of disturbed rocks and identify a potential major fractured plane down to about 1 km depth. Our studies may help to understand structures that host earthquakes in this area.

Description: Key Points: We use focusing prestack depth migration with detailed seismic data to analyze the complex subsurface environment of the Alpine Fault zone. Seismic images show Alpine Fault zone related reflectors at a depth of ∼0.2–1 km dipping ∼40°–56° around the DFDP‐2B borehole. Complex structures within the glacial Whataroa Valley are imaged showing steep valley flanks, faults, and internal sedimentary horizons.

Description: German Research Foundation (DFG)

Description: Earthquake Commission (EQC) http://dx.doi.org/10.13039/100012181

Description: NSERC discovery and Canada Research Chairs Program

Description: Canadian Foundation for Innovation