ALBERT

Description: Main aim of the project was to investigate the local seismicity (distribution and kinematics) within and around the Fergana basin and the Southern Tien Shan in Southern Kyrgistan. In order to achieve this goal a temporary local network was installed between 2009 and 2010. The results derived from this project contributed to decipher the relationship between geodynamics, neotectonic block structures and the occurrence of landslides in this region.

Description: This data publication provides a European assessment of building exposure, organized country-by-country. The dataset provides information about the number of buildings; the number of occupants; structural information and structural costs of buildings per geographical area. The main purpose of this data collection is risk assessment for natural hazards, however it can be used by anyone in need of a building exposure dataset. The data holds information about single buildings, with global estimates of built-up area on 10m x 10m pixels and exposure information per district. All OpenStreetMap (OSM) buildings existing in an OSM excerpt from 1 July 2023, 00:00 UTC (OpenStreetMap contributors, 2023), all buildings from the Global ML Building Footprint (GMLBF, Microsoft, 2023) dataset have been processed and for each building the occupancy type and number of stories have been identified based on data in OSM, such as land use and points of interest. The Global Human Settlement Built-up Characteristics 2022A Layer has been used as initial distribution of built area (Pesaresi, 2022). Aggregated exposure information, including the structural information and the number of occupants, stems the ESRM20 (Crowley et al., 2020). The resulting dataset is distributed per country as an SQLite/SpatiaLite database. Each database contains three tables and one view. The database is organized around three key concepts, that each have their own table. An Entity is a geographical unit that contains exposure. In this dataset, the entities are tiles in a multi-resolution grid, according to the Quad tree structure (Finkel & Bentley, 1974), with the tiles projected using the Web Mercator projection (EPSG:3857). The zoom-level of the Quadkeys inside the grid varies from level-15 to level-18, depending on the number of buildings inside each tile to preserve privacy-sensitive information. Practically, the size of the tiles varies between around 100m x 100m and 1km x 1km. Each entity consists of one or more Assets, defining the number of buildings of a particular structural type and their population and structural value. The structural type is described using a taxonomy string, describing for example structural properties, occupancy type and the expected number of stories. The exact definition of a taxonomy that is used in this dataset is described in the GEM Building Taxonomy v2.0 (Brzev et al., 2013). On top of the tables, one key view has been defined too. A view is essentially a query on the table that give some insights into the data. The `key_values_per_tile` provides the total number of buildings, total number of occupants at night and total structural costs summed over all assets in one tile entity.

Description: The dataset presents the greenhouse gas production (CO2 and CH4) from sediment of a terrestrial permafrost outcrop (Byk14-A-1; 71.85175°N, 129.350883°E), the thermokarst lake Goltsovoye (PG2412 (TKL), 71.74515°N, 129.30217°E), the nearly-closed Polar Fox Lagoon (PG2411 (LAG1), 71.743056°N, 129.337778°E) and the semi-open Uomullyakh Lagoon (PG2410-1 (LAG1), 71.730833°N, 129.2725°E). We incubated the samples anaerobically at 4 °C under fresh (c=0 g/L), brackish (c=13g/L) and marine (36g/L) conditions for one year and measured carbon dioxide (CO2) and methane (CH4) concentrations regularly in a 250 µL subsample using gas chromatography with an Agilent GC 7890A equipped with an Agilent HP-PLOT Q column. Cumulative CO2 and CH4 concentrations and production rates per day are given over time for all samples with three replicates each per gram of dry weight and normalised to gram of soil organic carbon (SOC).

Description: Groundwater contamination of the fractured aquifers by agricultural pollutants has been happening worldwide since more than a century, boosting the scientific research to develop new modelling approaches for reactive transport simulation in aquifers. Spatially implicit methods like travel time approaches have been gaining interest, attracting by their lower computational demand and flexibility. At the same time, detailed mechanistic models of reactive transport in the fractured systems allow percipient understanding of underlying geochemical processes and provide veritable quantification of the latter. In this work, we connect a spatially explicit model of denitrification and isotope transport, and analytical solutions of atrazine transport in the fractured system, with a spatially implicit travel time approach. The work aims to study reactive behaviour of agriculturally produced contaminants on the catchment scale and quantify the fractured system parameters of the Muschelkalk aquifer. Reactive transport modelling was employed for this purpose with MIN3P and analytical solutions for a single fracture. Reactive transport models included advective flow in the fracture as well as possible (multicomponent) diffusive exchange with the rock matrix and redox processes taking place along the flow path. Determination of the travel times and transport parameters is done by direct modelling of tritium, helium, radiogenic helium, and argon-39 isotopes and accounting for multicomponent diffusion and radioactive decay within the streamline. Stochastic simulations of the atrazine transport under parametric uncertainty were employed for predictive quantification of travel time-dependent groundwater vulnerability. Conceptual model selection of denitrification and investigation of the redox evolution on the catchment scale was done with the MIN3P code. Results were verified with observations made across the Ammer catchment. The gained knowledge highlights the significance of comprehensive process-based hydrogeochemical modelling along with an uncertainty assessment on the catchment scale. It also demonstrates the relevance of reactive transport modelling for correct calibration as a prerequisite for prediction of the long-term evolution and transport of solutes in groundwater.

Description: This data publication provides the results of the investigations and measurements of thermal rock properties conducted on site in the Tournemire field laboratory and at the Thermal Petrophysics Lab at GFZ. The thermal characterization of the clayey Jurassic (Upper Toarcian, ca. 180 My old) is contributing to the site characterization of the Tournemire Underground Research Lab (URL), located in Southern France. This URL is installed in a former railway tun-nel to better understand the physical processes resulting from thermal and hydrau-lic loading in a small fault zone in a highly consolidated shale formation (Bonnelye et al., 2023). At the Tournemire site, faults and fractures of different sizes extend from the surface (sedimentary cover) to the crystalline basement. At one specific gallery (Gallery East 03) installed in the former tunnel, thermally controlled in-situ fluid injection experiments are scheduled on a strike-slip fault zone outcropping at the URL (Bonnelye et al., 2023). In 2022, we visited the URL for baseline characteri-zation of thermal properties and to study the heterogeneity of the clay-dominated formation. Therefore, we took the chance to collect data and samples for a laborato-ry measurement campaign and to measure thermal conductivity in-situ in the tun-nel wall of Gallery East 03. The thermal data shall provide the baseline for the pa-rameterization of future numerical 3D models to better understand the thermal-hydraulic processes related to the experiment. This data publication provides the results of the investigations and measurements conducted on-site in the field la-boratory and at the Thermal Petrophysics Lab at GFZ.

Description: The formally named SP lava flow is a quartz-, olivine- and pyroxene-bearing basalt flow that is preserved in the desert climate of northern Arizona, USA. The flow has an 40Ar/39Ar age of 72 ± 4 ka (2σ) and has undergone negligible erosion and/or burial, making its surface an ideal site for direct calibration of cosmogenic nuclide production rates. Production rates for cosmogenic 3He (3Hec) and 21Ne (21Nec) have been determined from SP flow olivine and pyroxene in this study. The error-weighted mean, sea-level, high latitude (SLHL) total reference production rates of 3He in olivine and pyroxene have identical values of 135 ± 8 at/g/yr (2; standard error) using time-independent Lal (1991)/Stone (2000) (St) scaling factors. These production rates decrease to identical values of 130 ± 8 at/g/yr (2; standard error) when 3He measurements are standardized to the CRONUS-P pyroxene standard. The St-scaled, error-weighted mean, total reference production rates of 21Ne in olivine and pyroxene are 48.4 ± 2.9 at/g/yr and 26.5 ± 1.7 at/g/yr (2; standard error), respectively, increasing to 49.3 ± 3.0 at/g/yr and 27.0 ± 1.7 at/g/yr (2; standard error), respectively, when standardized to the CREU-1 quartz standard. 3He and 21Ne production rates (St) overlap within 2σ uncertainty with other St-scaled production rates in the literature. SLHL 3He and 21Ne production rates in SP flow olivine and pyroxene are nominally lower if time-dependent Lm and Sa scaling factors are used. Olivine and pyroxene both have identical, error-weighted mean SLHL production rates of 127 ± 8 at/g/yr (2; standard error) using Lm scaling factors and CRONUS-P standardized 3He measurements. These production rates decrease to identical values of 110 ± 7 at/g/yr (2; standard error) for olivine and pyroxene when using Sa scaling factors. The Lm-scaled, error-weighted mean, total reference production rates of 21Ne in olivine and pyroxene are 48.1 ± 2.8 at/g/yr and 26.4 ± 1.7 at/g/yr (2; standard error), respectively, when standardized to the CREU-1 quartz standard. The error weighted mean, local 21Ne/3He production rate ratio in olivine is 0.358 ± 0.009 (2; standard error), which increases to 0.378 ± 0.012 when using CREU-1 standardized 21Ne production rates and CRONUS-P standardized 3He production rates. The error weighted mean, local 21Ne/3He production rate ratio in pyroxene is 0.197 ± 0.006, or 0.208 ± 0.008 when 21Ne and 3He are standardized to CREU-1 and CRONUS-P, respectively. The updated, CREU-1 standardized 21Nec rate (St) in SPICE quartz is 16.5 ± 1.1 at/g/yr. Production of 21Ne in coexisting SPICE olivine (ol), pyroxene (px), and quartz (qz) (standardized to CREU-1; Fenton et al., 2019; this study) yields error-weighted mean, local production rate ratios of 3.00 ± 0.13 (2) and 1.64 ± 0.08 (2) for 21Neol/21Neqz and 21Nepx/21Neqz, respectively. This study suggests that production rates of 3He and 21Ne in SPICE olivine and pyroxene agree well with St- and Lm-scaled global mean production rates in the literature. It also indicates that CRONUS-P and CREU-1 standardizations yield production rates in even stronger agreement with these global mean rates.

Description: In subsurface projects where the host rock is of low permeability, fractures play an important role in fluid circulation. Both the geometrical and mechanical properties of the fracture are relevant to the perme- ability of the fracture. To evaluate this relationship, we numerically generated self-affine fractures reproducing the scaling relationship of the power spectral density (PSD) of the measured fracture sur- faces. The fractures were then subjected to a uniform and stepwise increase in normal stress. A fast Fourier transform (FFT)-based elastic contact model was used to simulate the fracture closure. The evolution of fracture contact area, fracture closure, and fracture normal stiffness were determined throughout the whole process. In addition, the fracture permeability at each step was calculated by the local cubic law (LCL). The influences of roughness exponent and correlation length on the fracture hy- draulic and mechanical behaviors were investigated. Based on the power law of normal stiffness versus normal stress, the corrected cubic law and the linear relationship between fracture closure and me- chanical aperture were obtained from numerical modeling of a set of fractures. Then, we derived a fracture normal stiffness-permeability equation which incorporates fracture geometric parameters such as the root-mean-square (RMS), roughness exponent, and correlation length, which can describe the fracture flow under an effective medium regime and a percolation regime. Finally, we interpreted the flow transition behavior from the effective medium regime to the percolation regime during fracture closure with the established stiffness-permeability function.

Description: Understanding the stability of magnesite in the presence of a hydrous fluid in the Earth’s upper mantle is crucial for modelling the carbon budget and cycle in the deep Earth. This study elucidates the behavior of magnesite in the presence of hydrous fluids. We examined the brucite magnesite (Mg(OH)2-MgCO3) system between 1 and 12 GPa by using synchrotron in situ energy dispersive X-ray diffraction experiments combined with textural observations from quenched experiments employing the falling sphere method. By subjecting magnesite to varying pressure-temperature conditions with controlled fluid proportion, we determined the stability limits of magnesite in the presence of a fluid and periclase. The observed liquidus provides insights into the fate of magnesite-bearing rocks in subduction zones. Our findings show that magnesite remains stable under typical subduction zone gradients even when infiltrated by hydrous fluids released from dehydration reactions during subduction. We conclude that magnesite can be subducted down to and beyond sub-arc depths. Consequently, our results have important implications for the carbon budget of the Earth’s mantle and its role in regulating atmospheric CO2 levels over geological timescales.

Description: Understanding how large river systems will respond to an invigorated hydrological cycle as simulated under higher global temperatures is a pressing issue. Insights can be gained from studying past wetter-than-present intervals, such as the North African Humid Period during the early Holocene Epoch (~11–6 thousand years ago). Here we present a 1,500-year-long annually laminated (varved) offshore sediment record that tracks the seasonal discharge of the Nile River during the North African Humid Period. The record reveals mobilization of large amounts of sediments during strong summer floods that may have rendered the Nile valley uninhabitable. More frequent and rapid transitions between extremely strong and weak floods between 9.2 and 8.6 thousand years ago indicate highly instable fluvial dynamics. Climate simulations suggest flood variability was paced by El Niño/Southern Oscillation on interannual timescales, while multi-decadal oscillatory modes drove changes in extreme flood events. These pacemakers have also been identified in the Nile flow records from the Common Era, which implies their stationarity under contrasting hydroclimatic conditions.

Description: Polar regions harbor a diversity of cold-adapted (cryophilic) algae, which can be categorized into psychrophilic (obligate cryophilic) and cryotrophic (non-obligate cryophilic) snow algae. Both can accumulate significant biomasses on glacier and snow habitats and play major roles in global climate dynamics. Despite their significance, genomic studies on these organisms remain scarce, hindering our understanding of their evolutionary history and adaptive mechanisms in the face of climate change. Here, we present the draft genome assembly and annotation of the psychrophilic snow algal strain CCCryo 101-99 (cf. Sphaerocystis sp.). The draft haploid genome assembly is 122.5 Mb in length and is represented by 664 contigs with an N50 of 0.86 Mb, a Benchmarking Universal Single-Copy Orthologs (BUSCO) completeness of 92.9% (n = 1519), a maximum contig length of 5.3 Mb, and a GC content of 53.1%. In total, 28.98% of the genome (35.5 Mb) contains repetitive elements. We identified 417 non-coding RNAs (ncRNAs) and annotated the chloroplast genome. The predicted proteome comprises 14,805 genes with a BUSCO completeness of 97.8%. Our preliminary analyses reveal a genome with a higher repeat content compared to mesophilic chlorophyte relatives, alongside enrichment in gene families associated with photosynthesis and flagella functions. Our current data will facilitate future comparative studies, improving our understanding of the likely response of polar algae to a warming climate as well as their evolutionary trajectories in permanently cold environments.

Description: On 6 February 2023, a devastating earthquake doublet consisting of 7.8 and 7.6 events separated by about 9 hr struck the southeastern part of Türkiye. The developing aftershock sequence contained thousands of events during the first few days and overwhelmed the routine algorithms handling their detection and location. In addition, several stations temporarily lost real‐time contact and came online again later. At the same time the Omori decay of the aftershock event rate reduced the event frequency and allowed for inclusion of progressively smaller‐magnitude events with time. One possibility to help deal with such a complex situation is the use of machine learning (ML) methods to generate earthquake catalogs with a substantially higher number of events. Here, we present high‐resolution earthquake catalogs derived with two ML association methods for the first five days of the aftershock sequence of this doublet. In terms of the number of reliably located events, the event catalog created from PhaseNet picks and the GENIE phase association method outperforms both the routine regional catalog and the second ML‐derived catalog obtained from the GaMMA phase association method. Although both GaMMA and GENIE catalogs detect about 6 times more events than the routine catalog, GENIE associates on average about double the phases to a single event than GaMMA, which results in better constrained event locations. The spatiotemporal evolution of the event rates is sensitive to changes in the network geometry due to variable station availability. During the first few days, no decay of the event rate in the enhanced catalog is observed due to the inclusion of progressively smaller‐magnitude events with time and increased station availability. This study indicates that ML‐derived earthquake catalogs for challenging time periods like the early aftershock sequences of large earthquakes have the potential to significantly improve routine event catalogs.

Description: The Hatshepsut temple in Egypt is a masterpiece of ancient architecture. Just as distinct as the temple itself is the rock formation it is carved into, and recurring rock falls in the vicinity have raised concerns regarding the temple’s safety under progressing erosion and seismic activity. Due to the material characteristics (brittle carbonate rock), high stresses could lead to rapid crack propagation, and vibra-tion-based measures may be suitable precursors for imminent rock falls. This paper describes a two-day measurement campaign on the rock towers as a preliminary study prior to the implementation of a long-term seismic station. Next to operational modal analysis, horizontal-to-vertical spectral ratios, and standard spectral ratios are evaluated to cross-validate the resonance behaviour. To the author’s knowledge, this is the first study where stochastic subspace identification (SSI) is applied for the estimation and automated tracking of natural frequencies, mode shapes, and damping ratios in rock formations. One of the advantages of this method is the inherent uncertainty quantification, meaning for each vibration record, the mean values and the standard deviations are estimated for each modal parameter, giving deep insights into the reliability of the vibration-based monitoring of rock formations.

Description: The present review of published data as well as the new results demonstrate the versatility of conodonts in documenting and explaining global environmental fluctuations related to the Kačák Episode (KE) in the latest Eifelian. Although the conodont zonation of the KE interval is ambiguous and requires revision, the compilation of conodont stratigraphic ranges shows their potential for a precise worldwide correlation of relevant marine strata. Conodont biofacies may serve to document environmental changes connected with KE, in particular the sealevel rise at its beginning, followed by a regressive trend. Nevertheless, the familiar Icriodus/Polygnathus ratio should be carefully applied as an indication of water depth and nearshore vs. offshore position, being controlled also by other factors, such as paleolatitude and/or climate. Oxygen isotopes in conodont apatite, studied using secondary ion mass spectrometry technique evidence a warming at the onset of KE, based on the new data from the open marine facies of the Prague Basin. At the same time, they indicated climate-controlled salinity fluctuations in the epeiric Belarusian Basin. The present investigations as well as previous results suggest caution when analyzing thermally altered conodonts which may result in biased oxygen isotope signatures. The present experience suggests the conodont colour alteration index CAI 3 as a boundary value above which the caution is necessary.

Description: Drilling into the Earth is important for collecting resources like water and raw materials, and it is also done for scientific reasons, to learn about the planet. A method called rotary drilling is often used to drill holes deep into the Earth. To understand how deep we can drill, you need to understand how rotary drilling is performed and what the challenges are. This article explains how we drill deep holes and introduces the equipment needed for rotary drilling. The deeper we drill into the Earth, the higher the temperature and pressure. As temperature and pressure increase, drilling equipment will eventually fail. Another challenge is preventing the hole from collapsing. We will explain how these challenges can be tackled and how deep we can drill with current drilling techniques.

Description: Climate contrasts across drainage divides, such as orographic precipitation, are ubiquitous in mountain ranges, and as a result, mountain topography is often asymmetric. During glacial periods, these climate gradients can generate asymmetric glaciation, which may modify topographic asymmetry and drive divide migration during glacial-interglacial cycles. Here we quantify topographic asymmetry caused by asymmetric glaciation and its sensitivity to different climate scenarios. Using an analytical model of a steady-state glacial profile, we find that the degree of topographic asymmetry is primarily controlled by differences in the equilibrium line altitude across the divide. Our results show that glacial erosion can respond to the same climate asymmetry differently than fluvial erosion. When there are precipitation differences across the divide, glacial erosion produces greater topographic asymmetry than fluvial erosion, all else equal. These findings suggest that glaciations may promote drainage reorganization and landscape transience in intermittently glaciated mountain ranges.

Description: Earthquakes are rupture-like processes that propagate along tectonic faults and cause seismic waves. The propagation speed and final area of the rupture, which determine an earthquake’s potential impact, are directly related to the nature and quantity of the energy dissipation involved in the rupture process. Here, we present the challenges associated with defining and measuring the energy dissipation in laboratory and natural earthquakes across many scales. We discuss the importance and implications of distinguishing between energy dissipation that occurs close to and far behind the rupture tip, and we identify open scientific questions related to a consistent modeling framework for earthquake physics that extends beyond classical Linear Elastic Fracture Mechanics.

Description: This paper investigates the potential of performing orbit determination directly in the Earth-fixed frame based on Inter-Satellite Ranging (ISR) measurements as primary observables, combined with Ground-to-Satellite Ranging (GSR) measurements from a small regional ground network. Current Global Navigation Satellite Systems (GNSSs) use L-band pseudo-range and carrier phase measurements from global or regional ground station networks to perform dynamic Orbit Determination and Time Synchronization (ODTS), whereas sparse Satellite Laser Ranging measurements are mainly used for validation. Future GNSSs may be equipped with inter-satellite links (ISLs) to enable inter-satellite clock offset estimation, ranging and data relay. These capabilities carry the potential to significantly improve ODTS procedures. In this work, we assume a fully connected constellation via pair-wise ISLs, with measurement topology assigned by appropriate link schedulers. The satellite orbits are parametrized with the standard 15 Galileo broadcast perturbed Keplerian elements, estimated by using ISR and GSR measurements. This processing strategy eliminates the complex modeling of gravitational and non-gravitational forces, making it particularly suitable for on-board applications and offering an alternative to classical GNSS orbit determination processing architectures. The proposed orbit determination scheme can be used in case of a ground segment failure as a back-up procedure to estimate the orbits of the GNSS satellites onboard of each satellite and guaranteeing a continuous navigation message generation for the system users. The performance of the proposed method depends on a number of factors, such as the length of the data fitting interval, the measurement quality (precision and accuracy), the scheduling and geometry of ISR and GSR measurements, the number and distribution of ground stations, and the accuracy of the ground station coordinates. Preliminary results show that an orbit-only Signal-in-Space Range Error (SiSRE) in the order of 7–9 cm can be obtained by processing 2 to 3 h data with a limited set of supporting ground stations. In this study, the orbit determination scheme proposed is tested on different scenarios, providing a first assessment of attainable performance.

Description: In streams, short‐term element‐specific solute fluxes are often not balanced with long‐term chemical weathering fluxes determined in the residual solids from fractional element loss and denudation rate. The ratio of both estimates—the “Dissolved Export Efficiency” (DEE)—is frequently 〈1, indicating deficits in the stream dissolved load. To explore the cause of the stream deficits, we performed a daily water sampling campaign for one year in a forested headwater watershed in Southern Germany. We sampled surface runoff, above‐canopy and below‐canopy precipitation, subsurface flow from the organic soil layer, upper, and deep mineral soil, and groundwater. Regolith samples were obtained from a drill core and revealed the weathering front to lie between 7 and 15 m depth. We found a DEE 〈 1 for K, Si, Al, Fe. These elements are characterized by shallow slopes in C‐Q relationships, and the imbalances were found to originate in the deep saprolite. Their export pathway potentially includes “hidden” Critical Zone compartments or fluxes, presumably unsampled colloids that are exported preferentially during rare flushing events with stochastic temporal distribution. The DEE of nutritive elements like Ca, Mg, and P is also 〈1. These elements are characterized by steeper C‐Q slopes, and their imbalance can be explained by deep nutrient uptake followed by nutrient retainment in re-growing forest biomass or export in plant debris. The collective evidence for these imbalances, including previous evidence from metal stable isotopes, suggests that the deep Critical Zone represents the location for chemical or biogenic retention and release of solutes.

Description: The BASE (Barberton Archean Surface Environments) scientific drilling project aimed at recovering an unweathered continuous core from the Paleoarchean Moodies Group (ca. 3.2 Ga), central Barberton Greenstone Belt (BGB), South Africa. These strata comprise some of the oldest well-preserved sedimentary strata on Earth, deposited within only a few million years in alluvial, fluvial, coastal-deltaic, tidal, and prodeltaic settings. They represent a very-high-resolution record of Paleoarchean surface conditions and processes. Moodies Group strata consist of polymict conglomerates, widespread quartzose, lithic and arkosic sandstones, siltstones, shales, and rare banded-iron formations (BIFs) and jaspilites, interbedded with tuffs and several thin lavas. This report describes objectives, drilling, and data sets; it supplements the operational report. Eight inclined boreholes between 280 and 495 m length, drilled from November 2021 through July 2022, obtained a total of 2903 m of curated core of variable quality through steeply to subvertically dipping, in part overturned stratigraphic sections. All drilling objectives were reached. Boreholes encountered a variety of conglomerates, diverse and abundant, mostly tuffaceous sandstones, rhythmically laminated shale-siltstone and banded-iron formations, and several horizons of early-diagenetic silicified sulfate concretions. Oxidative weathering reached far deeper than expected. Fracturing was more intense, and BIFs and jaspilites were thicker than anticipated. Two ca. 1 km long mine adits and a water tunnel, traversing four thick stratigraphic sections within the upper Moodies Group in the central BGB, were also sampled. All boreholes were logged by downhole wireline geophysical instruments. The core was processed (oriented, slabbed, photographed, described, and archived) in a large, publicly accessible hall in downtown Barberton. A geological exhibition provided background explanations for visitors and related the drilling objectives to the recently established Barberton Makhonjwa Mountains World Heritage Site. A substantial education, outreach, and publicity program addressed the information needs of the local population and of local and regional stakeholders.

Description: The increasing importance of Earth observation information for society and environment, particularly in the expanding domain of hyperspectral remote sensing, along with the significantly increasing data availability, emphasizes the demand for online education to address the growing need for expertise in this domain. We present a comprehensive review of existing online education programs on Earth observation that underline the limited availability of online resources for hyperspectral remote sensing. To respond to this demand, we introduce HYPERedu, an online education program on hyperspectral remote sensing that has been developed as part of the EnMAP satellite mission since 2019. The program’s core components, content, and participation statistics, along with insights from participant feedback, are presented. HYPERedu offers a wide range of resources, including slide collections, tutorials, video screencasts, and online courses, making them accessible to a broad audience for university teaching, training schools and individual learning. The program’s effectiveness as well as challenges and insights encountered during program development are discussed. We emphasize the importance of collaborative learning, sustainability efforts for long-term material accessibility and quality assurance, and the need to bridge the digital divide with offline options, opensource tools, and multilingual content. Effective content presentation is vital, focusing on consistent branding, concise modules, interactive features, and narrative-style videos. Additionally, we explore the future of online Earth observation learning, considering enhanced participant interaction and the integration of new learning concepts. Finally, we underscore the significance of outreach and training for satellite mission utilization and advocate for open education to promote open science, data, software, and accessibility for inclusive education.

Description: Central Afar is shaped by the interaction between the Red Sea (RS) and Gulf of Aden (GoA) rifts. While there have been several studies conducted in the region, we know surprisingly little about the mechanism of connection between these two rift branches. Here we use high-resolution 3D lithospheric scale geodynamic modeling to capture the evolution of linkage between the RS and GoA rifts in central Afar. Our results demonstrate that the two rifts initially overlap and interact across a broad zone of faulting and vertical axis block rotation. However, through time, rift overlap is abandoned in favor of direct linkage which generates a series of localized en-echelon basins. The present-day direct linkage between the two rifts is supported by geodetic observations. Our study reconciles previously proposed models for the RS and GoA rift connection by considering spatial and temporal evolution of the rifts.

Description: Enhanced geothermal systems (EGSs) developed by hydraulic stimulation are promising for exploiting petrothermal heat by improving fluid pathways in low-permeable geothermal reservoir rocks. However, fluid injection into the subsurface can potentially cause large seismic events by reactivating pre-existing faults, which is a significant barrier to EGSs. The management of injection-induced seismicity is, therefore, essential for the success of EGSs. During the hydraulic stimulation of an EGS, fluid can be injected into a fault zone or into the rock matrix containing pre-existing faults adjacent to the injection well. The differences in hydromechanical responses between fluid injection into and adjacent to a fault have not been investigated in detail. Here, we performed triaxial fluid injection experiments involving injecting fluid directly and indirectly into a fault in granite rock samples to analyse the distinct hydromechanical responses and estimate the injection-induced seismicity in both cases. Our results suggest that in addition to directly injecting fluid into a critically stressed fault, injecting into nearly intact granite adjacent to the fault could also cause injection-induced seismic hazards owing to the high fluid pressure required to create new fractures in the granite matrix. It is, therefore, important to carefully identify pre-existing faults within tight reservoirs to avoid injecting fluid adjacent to them. Additionally, once prior unknown faults are delineated during hydraulic stimulation, appropriate shut-in strategies should be implemented immediately to mitigate seismic risks.

Description: Fault slip is a complex natural phenomenon involving multiple spatiotemporal scales from seconds to days to weeks. To understand the physical and chemical processes responsible for the full fault slip spectrum, a multidisciplinary approach is highly recommended. The Near Fault Observatories (NFOs) aim at providing high-precision and spatiotemporally dense multidisciplinary near-fault data, enabling the generation of new original observations and innovative scientific products. The Alto Tiberina Near Fault Observatory is a permanent monitoring infrastructure established around the Alto Tiberina fault (ATF), a 60 km long low-angle normal fault (mean dip 20°), located along a sector of the Northern Apennines (central Italy) undergoing an extension at a rate of about 3 mm yr−1. The presence of repeating earthquakes on the ATF and a steep gradient in crustal velocities measured across the ATF by GNSS stations suggest large and deep (5–12 km) portions of the ATF undergoing aseismic creep. Both laboratory and theoretical studies indicate that any given patch of a fault can creep, nucleate slow earthquakes, and host large earthquakes, as also documented in nature for certain ruptures (e.g., Iquique in 2014, Tōhoku in 2011, and Parkfield in 2004). Nonetheless, how a fault patch switches from one mode of slip to another, as well as the interaction between creep, slow slip, and regular earthquakes, is still poorly documented by near-field observation. With the strainmeter array along the Alto Tiberina fault system (STAR) project, we build a series of six geophysical observatory sites consisting of 80–160 m deep vertical boreholes instrumented with strainmeters and seismometers as well as meteorological and GNSS antennas and additional seismometers at the surface. By covering the portions of the ATF that exhibits repeated earthquakes at shallow depth (above 4 km) with these new observatory sites, we aim to collect unique open-access data to answer fundamental questions about the relationship between creep, slow slip, dynamic earthquake rupture, and tectonic faulting.

Description: Dynamic failure in the laboratory is commonly preceded by many foreshocks which accompany premonitory aseismic slip. Aseismic slip is also thought to govern earthquake nucleation in nature, yet, foreshocks are rare. Here, we examine how heterogeneity due to different roughness, damage and pore pressures affects premonitory slip and acoustic emission characteristics. High fluid pressures increase stiffness and reduce heterogeneity which promotes more rapid slip acceleration and shorter precursory periods, similar to the effect of low geometric heterogeneity on smooth faults. The associated acoustic emission activity in low-heterogeneity samples becomes increasingly dominated by earthquake-like double-couple focal mechanisms. The similarity of fluid pressure increase and roughness reduction suggests that increased stress and geometric homogeneity may substantially shorten the duration of foreshock activity. Gradual fault activation and extended foreshock activity is more likely observable on immature faults at shallow depth.

Description: Cosmic radiation near the Earth's surface is influenced by solar activity, atmospheric conditions, and changes of nearby soil moisture or snow. To better understand how cosmic‐ray neutron measurements should be corrected for meteorological effects, we operated a detector for low‐energy neutrons in a buoy on a lake in Germany for 5 months in 2014. Since the water content in the surroundings is constant, we were able to isolate the signal from almost any ground‐related disturbances. With this instrument, we challenged traditional and recent theories on the neutron response to water, air humidity, and to reference data from high‐energy neutron monitors around the world. We found that in some cases, recent theories showed superior performance over traditional approaches. We also found a stronger response of the neutrons detected by the buoy to a major solar event than was observed by traditional neutron monitors. The concept of a neutron detector on a lake could be useful as a reference station for similar land‐side detectors and help provide more reliable soil moisture products.

Description: The German Research Centre for Geosciences (GFZ) in Potsdam hosts a CAMECA 1280-HR large geometry secondary ion mass spectrometer (SIMS) with a web-based user node at the University of the Witwatersrand, South Africa. A major theme of our facility is high-precision, high-accuracy, high-spatial resolution analyses of light isotope ratios in a variety of natural and experimental materials. The latest analytical developments from the GFZ SIMS laboratory focus on the development, assessment and use of new reference materials for stable isotope analysis. Particularly for oxygen, our repeatability from 15-µm diameter domains is now typically better than ±0.15‰ (1s). However, the total uncertainty on such analyses is commonly larger because of significant differences (in some cases more than one ‰) among the isotope ratios of reference materials reported by multiple, highly regarded gas source mass spectrometry laboratories. This issue of interlaboratory bias during reference material characterization inevitably impacts all in situ data employing such materials and must be duly considered.

Description: Here we report on a set of six apatite reference materials (chlorapatites MGMH# 133648, TUBAF# 38 and fluorapatites MGMH# 128441A, TUBAF# 37, 40, 50) which we have characterised for their chlorine isotope ratios; these RMs span a range of Cl mass fractions within the apatite Ca10(PO4)6(F,Cl,OH)2 solid solution series. Numerous apatite specimens, obtained from mineralogical collections, were initially screened for 37Cl/35Cl homogeneity using SIMS followed by δ37Cl characterisation by gas source mass spectrometry using both dual‐inlet and continuous‐flow modes. We also report major and key trace element compositions as determined by EPMA. The repeatability of our SIMS results was better than ± 0.10‰ (1s) for the five samples with 〉 0.5% m/m Cl, and ± 0.19‰ (1s) for the low Cl abundance material (0.27% m/m). We also observed a small, but significant crystal orientation effect of 0.38‰ between the mean 37Cl/35Cl ratios measured on three oriented apatite fragments. Furthermore, the results of GS‐IRMS analyses show small but systematic offset of δ37ClSMOC values between the three laboratories. Nonetheless, all studied samples have comparable chlorine isotope compositions, with mean 103δ37ClSMOC values between +0.09 and +0.42 and in all cases with 1s ≤ ± 0.25.

Description: Ab Weihnachten 2023 kam es zu einer Hochwassersituation vor allem im Bereich der Flüsse Ems, Weser und Elbe, welche bis in den Januar 2024 hinein zu einer angespannten Lage vor allem in weiten Teilen Nordwestdeutschlands führte. Dieses Winterhochwasser wurde ausgelöst durch großräumige Dauerniederschläge vor allem in Norddeutschland über Weihnachten 2023 (19.-25.12.2023) und verstärkt durch nachfolgende, wenn auch schwächere Niederschlagsereignisse bis Anfang Januar 2024, welche darüber hinaus auf bereits gesättigte Böden trafen. Die Ungewöhnlichkeit des Weihnachtsniederschlagsereignisses bestand in seiner großen räumlichen Ausdehnung und langen zeitlichen Andauer von sieben Tagen. Es hing zusammen mit einer Wetterlage (charakterisiert durch ein ausgedehntes Tiefdrucksystem mit Zentrum über Südskandinavien), welche an sich nicht außergewöhnlich war, jedoch extrem lange andauerte. Das spezifische räumliche Muster dieses einwöchigen Niederschlagsereignisses war auch in der Vergangenheit sowohl mit ergiebigen Dauerniederschlägen als auch mit der zuvor erwähnten Wetterlage assoziiert. Die nachfolgenden Niederschlagsereignisse Ende Dezember und Anfang Januar waren für sich betrachtet wesentlich schwächer. Deren zeitliches Zusammenspiel mit dem vorherigen Weihnachtsereignis führte jedoch dazu, dass gebietsweise über lange Zeiträume von bis zu zweieinhalb Wochen extreme mittlere Niederschlagsintensitäten auftraten. Das Hochwasser als Auswirkung der Niederschläge war ebenfalls im Wesentlichen durch seine große räumliche Ausdehnung charakterisiert, nur vereinzelt wurden extreme Flusspegelstände gemessen. Unter allen Hochwassern in Deutschland seit 1955 (für welche die Abflüsse über zwei Wochen eine Wiederkehrzeit von mindestens 10 Jahren aufwiesen) rangiert die räumliche Ausdehnung des Weihnachtshochwassers 2023 mit gut 100.000 km² auf Platz 9. Die räumliche Ausdehnung ist hierbei nicht die Überflutungsfläche, sondern die Fläche, in der die Hochwasserabflüsse einen bestimmten Schwellenwert überschreiten. Die Überflutungsfläche selbst erreichte eine Ausdehnung von ca. 1000 km² und betraf mehr als 40 Landkreise, vor allem in Niedersachsen und Bremen, aber auch in Teilen Hessens und Nordrhein-Westfalens. Betroffen waren dabei, je nach Abschätzung, 18.000 bis 30.000 Personen, rund 2000 Gebäude, 4,6 km² bebaute Fläche und 470 km Straßen. Die im Dezember 2023 gemessene Monatsniederschlagssumme von 164 mm (über einem besonders von den Niederschlägen betroffenen Gebiet in Niedersachsen: 51,5°N - 53,5°N, 8,0°O - 11,0°O) tritt in den Wintermonaten im heutigen Klima durchschnittlich nur ca. alle 120 Jahre auf. Eine Attributionsstudie des Deutschen Wetterdienstes (DWD) zeigt, dass sich die Wahrscheinlichkeit für ein Ereignis dieser Intensität aufgrund der bisherigen Klimaerwärmung von 1,2°C (seit etwa 1900) um den Faktor 1,8 (Ergebnisspanne: 0,1 bis 140) erhöht hat, und dass sich diese Wahrscheinlichkeit im Falle eines 2°C wärmeren Klimas, d.h. einer zusätzlichen Erwärmung um weitere 0,8°C, nochmals erhöhen wird. Die Studie zeigt jedoch auch, dass diese Abschätzungen mit großen Unsicherheiten verbunden sind. Dennoch sind diese Abschätzungen konsistent mit den Ergebnissen verschiedener Studien, welche sowohl eine Zunahme des mittleren Winterniederschlags zeigen als auch eine Intensivierung extremer Niederschlagsereignisse im nördlichen Mitteleuropa.

Description: As a population parameter, obtaining a reliable estimation of the b-value is inherently complex, especially when considering spatial variability. To tackle this issue, we adopt an approach that treats the spatial b-value distribution as a non-stationary Gauss process for the underlying earthquake-realizing Poisson process. For Gauss process inference, it is necessary to specify the covariance, which in this context describes the spatial correlation of the b-value, a priori. We formulate the anisotropic covariance as another Gauss process based on the local fault structure. The covariance anisotropy characterizes, in terms of the b-value, the correlation between earthquakes on a fault, which is higher than between an on-fault earthquake and an off-fault earthquake (or an event on another fault). This adaptive feature captures the geological structure more effectively than an isotropic covariance or similarly defined and commonly used running-window estimates of the b-value. In our research, we demonstrate the Bayesian inference of the Gauss process b-value estimation for several regions with dense earthquake catalogs and fault catalogs, such as southern California based on the SCEDC earthquake catalog and UCERF3 fault model. Our model provides a continuous b-value estimate (including its uncertainties) that reflects the local fault structure to a very high degree. We can associate the b-value with the local seismicity distribution and major faults with higher resolution than conventional (isotropic) estimation methods. Furthermore, in light of the Turkish earthquake sequence in 2023, we also assess the spatial variability of the b-value of aftershocks and their association with various faults in the region.

Description: Distributed acoustic sensing (DAS) sees increased utilization in the seismological community in recent years and various applications are investigated for the usage of DAS in different branches of seismology. Strong-motion seismology uses records of earthquakes of engineering concern (MW〉4.5) with hypocentral distances within few hundreds of kilometers. This demands dense networks over a wide area and installation of typical strong-motion instruments (accelerometers) can be achieved quickly and at a reasonable budget, compared to other network types. For DAS, installation and operation are more involved, and deployment is very still limited. Consequently, DAS recordings of nearby large events are still very unlikely and rare compared to accelerometers. On September 18, 2022, a shallow earthquake sequence with a M〈sub〉W〈/sub〉 6.9 mainshock struck near Chishang (Taiwan) and was recorded by DAS in Hualien city, appr. 100 km north. Shaking of the mainshock and several aftershocks were noticeable in Hualien, though not damaging with PGA recorded at 0.28 m/s^2 nearby the DAS site. The DAS campaign was originally conceptualized as a test suite with different fiber installations: including buried, within a gutter (as in commercial fiber installation) and loose within a basement. The test site is in an urban area affected by surface rupturing during the 2018 Hualien earthquake. The presented recordings provide not only an unprecedented insight how strong-motion appears on DAS but also how effective different installation techniques are for this kind of event. The waveforms are also compared to records of a collocated broadband seismometer and an accelerometer 1 km away.

Description: Distributed Acoustic Sensing (DAS) is used to record high-spatial resolution strain-rate data. For ground motion observation, the DAS data can be converted from strain rate to acceleration or velocity by array-based measurements with coherent plane waves. DAS provides an opportunity to map high-resolution shaking patterns near faults. We installed collocated geophones and optical fiber in Hualien City (a very seismically active area in Taiwan) from the end of January to the end of February in 2022. Earthquakes with magnitudes (Mw) between 3.2 and 5.4 have been recorded. These records illustrate the typical magnitude-distance dependence of ground-motion but also show saturation for higher magnitudes and/or at shorter distances (e.g for an earthquake of Mw 5.2 earthquake recorded at 100 km). For frequency-based analyses, clipped signals on DAS result in challenges not present in classical instruments (seismometers). The upper limit in dynamic range of seismometers results in easily identifiable trapezoidal signals. The dynamic range of DAS interrogators is limited by gauge length, sampling frequency, and wrapped phase in the interferometric phase demodulation. We observe that clipped DAS signals not only affect time series but also contaminate their spectra on all frequencies, due to the random nature of clipping in DAS—contrasting to the flat plateaus in clipped time series on seismometers. Therefore, the identification of the start and end points of clipped DAS records poses a major challenge, which we aim to resolve with a neural network. This approach enhances the efficiency for quality control of massive DAS datasets.

Description: Rapid assessment of an earthquake’s impact on the affected society is a crucial first step of disaster management, determining further emergency measures. We demonstrate that macroseismic observations, collected as felt reports via the LastQuake service of the European Mediterranean Seismological Center, can be utilized to estimate the probability of a felt earthquake to have a “high impact” rather than a “low impact” on the affected population on a global scale. In our fully data-driven, transparent, and reproducible approach we compare the distribution of felt reports to documented earthquake impact in terms of economic losses, number of fatalities, and number of damaged or destroyed buildings. Using the distribution of felt-reports as predictive parameters and an impact measure as the target parameter, we infer a probabilistic model utilizing Bayes’ theorem and Kernel Density Estimation, that provides the probability of an earthquake to be “high impact”. For 393 felt events in 2021, a sufficient number of felt reports to run the model is collected within 10 minutes after the earthquake. While a clean separation of “high-impact” and “low-impact” events remains a challenging task, unambiguous identification of many “low-impact” events in our dataset is identified as a key strength of our approach. We consider our method a complementary and inexpensive impact assessment tools, that can be utilized instantly in all populated areas on the planet, with the necessary technological infrastructure. Being fully independent of seismic data, our framework poses an affordable option to support disaster management in regions that currently lack expensive seismic instrumentation.

Description: The Taiwan Milun fault zone located at the boundary between the Eurasian and Philippine Sea plates. This fault slips frequently and produced large earthquakes, as for example the Mw6.4 Hualien earthquake (6 February 2018). We map and observe the fault zone and its behavior at depth by high spatial resolution dynamic strain sensing with optical fiber. In 2021-2022, we drilled and cored the fault, and deployed a 3D multi-cross-fault fiber array comprising a borehole loop with a depth of 700 m (Hole-A, Hanging wall site, crossing the fault at depth), a surface array crossing the fault rupture zone using commercial fiber, and a second borehole loop of 500m fiber (Hole-B, Footwall site). The high spatial resolution from distributed acoustic sensing (DAS) and the retrieved core combined with geophysical logs allow us to characterize the structure on meter-scale. Within the Milun fault zone, we identified a 20-m wide fault core comprised of gray and black gouge in the core sample. DAS strain-rate records associated with the same depth as the fault core show a distinct amplification. The amplification ratio of 2.5-3 is constant as for all types of events (local, teleseismic ), when compared to DAS channels at larger depth, related to a consolidated rock material. Although the fault gouge is narrow, the nature of the amplification in strain is due to its strong material contrast from fault gouge. This result may shed the light on the understanding of fault-zone dynamics in terms of remote earthquake triggering and near-fault ground motion.

Description: As a population parameter, reliable estimation of the b-value is intrinsically complicated, particularly when spatial variability is considered. We approach this issue by treating the spatial b-value distribution as a non-stationary Gaussian process for the underlying earthquake-realizing Poisson process. For Gaussian process inference the covariance—which describes here the spatial correlation of the b-value—must be specified a priori. We base the covariance on the local fault structure, i.e. the covariance is anisotropic: elongated along the dominant fault strike and shortened when normal to the fault trace. This adaptive feature captures the geological structure better than an isotropic covariance or similarly defined and commonly used running-window estimates of the b-value. We demonstrate the Bayesian inference of the Gaussian process b-value estimation for two regions: California based on SCEDC earthquake and Turkey based on the AFAD earthquake catalog. The covariances in the inferences are calibrated with the SCEC community fault model the GEM fault model for California and Turkey, respectively. Our model provides a continuous b-value estimate (including its uncertainties) which reflects the local fault structure to a very high degree. We are able to associate the b-value with the local seismicity distribution and link it to major faults. In light of the recent Turkish earthquake sequence, we also assess the temporal evolution of the b-value of recent seismicity before and after major events.

Description: Stress maps show the orientation of the current maximum horizontal stress (SHmax) in the earth's crust. Assuming that the vertical stress (SV) is a principal stress, SHmax defines the orientation of the 3D stress tensor; the minimum horizontal stress Shmin is than perpendicular to SHmax. In stress maps SHmax orientations are represented as lines of different lengths. The length of the line is a measure of the quality of data and the symbol shows the stress indicator and the color the stress regime. The stress data are freely available and part of the World Stress Map (WSM) project. For more information about the data and criteria of data analysis and quality mapping are plotted along the WSM website at http://www.world-stress-map.org. The stress map of Taiwan 2022 is based on the WSM database release 2016. However, all data records have been checked and we added a large number of new data from earthquake focal mechanisms from the national earthquake catalog and from publications. The total number of data records has increased from n=401 in the WSM 2016 to n=6,498 (4,234 with A-C quality) in the stress map of Taiwan 2022 The update with earthquake focal mechanims is even larger since another 1313 earthquake focal mechanism data records beyond the scale of this map have been added to the WSM database. The digital version of the stress map is a layered pdf file generated with GMT (Wessel et al., 2019). It also provide estimates of the mean SHmax orientation on a regular 0.1° grid using the tool stress2grid (Ziegler and Heidbach, 2019). Two mean SHmax orientations are estimated with search radii of r=25 and 50 km, respectively, and with weights according to distance and data quality. The stress map and data are available on the landing page at https://doi.org/10.5880/WSM.Taiwan2022 where further information is provided. The earthquake focal mechanism that are used for this stress map are provided by the Taiwan Earthquake Research Center (TEC) available at the TEC Data Center (https://tec.earth.sinica.edu.tw).

Description: This data set contains measurements of an underground hydraulic fracture experiment at Äspö Hard Rock Laboratory in May and June 2015. The experiment tested various injection schemes for rock fracture stimulation and monitored the resulting seismicity. The primary purpose of the experiment is to identify injection schemes that provide rock fracturing while reducing seismicity or at least mitigate larger seismic events. In total, six tests with three different injection schemes were performed in various igneous rock types. Both the injection process and the accompanied seismicity were monitored. For injection monitoring, the water flow and pressure are provided and additional tests for rock permeability. The seismicity was monitored in both triggered and continuous mode during the tests by high-resolution acoustic emission sensors, accelerometers and broadband seismometers. Both waveform data and seismicity catalogs are provided.

Description: In this study, we propose a statistical method to validate sea-level reconstructions using geological records known as sea-level indicators (SLIs). SLIs are often the only available data to retrace late-glacial relative sea level (RSL). Determining the RSL from SLI height is not straight forward, the elevation at which an SLI was found usually does not represent the past RSL. In contrast, it has to be related to past RSL by investigating sample’s type, habitat and deposition conditions. For instance, water distribution at which a specific specimen is found today can be related to the indicator's depositional height range. Furthermore, the precision of dating varies between geological samples, and, in case of radiocarbon dating, the age has to be calibrated using a non-linear calibration curve. To avoid an a-priori assumption like normal-distributed uncertainties, we define likelihood functions which take into account the indicative meaning’s available error information and calibration statistics represented by joint probabilities. For this conceptional study, we restrict ourselves to one type of indicators, shallow-water shells, which are usually considered as low-grade samples giving only a lower limit of former sea level, as the depth range in which they live spreads over several tens of meters, and does not follow a normal distribution. The presented method is aimed to serve as a strategy for glacial isostatic adjustment reconstructions, in this case for the German Paleo-Climate Modelling Initiative PalMod (https://www.palmod.de/en) and by extending it to other SLI types.

Description: In this article, a high-resolution acoustic emission sensor, accelerometer, and broadband seismometer array data set is made available and described in detail from in situ experiments performed at Äspö Hard Rock Laboratory in May and June 2015. The main goal of the hydraulic stimulation tests in a horizontal borehole at 410m depth in naturally fractured granitic rock mass is to demonstrate the technical feasibility of generating multi-stage heat exchangers in a controlled way superiorly to former massive stimulations applied in enhanced geothermal projects. A set of six, sub-parallel hydraulic fractures is propagated from an injection borehole drilled parallel to minimum horizontal in situ stress and is monitored by an extensive complementary sensor array implemented in three inclined monitoring boreholes and the nearby tunnel system. Three different fluid injection protocols are tested: constant water injection, progressive cyclic injection, and cyclic injection with a hydraulic hammer operating at 5 Hz frequency to stimulate a crystalline rock volume of size 30m30m30m at depth. We collected geological data from core and borehole logs, fracture inspection data from an impression packer, and acoustic emission hypocenter tracking and tilt data, as well as quantified the permeability enhancement process. The data and interpretation provided through this publication are important steps in both upscaling laboratory tests and downscaling field tests in granitic rock in the framework of enhanced geothermal system research. Data described in this paper can be accessed at GFZ Data Services under https://doi.org/10.5880/GFZ.2.6.2023.004 (Zang et al., 2023).

Description: We construct and examine the prototype of a deep learning-based ground-motion model (GMM) that is both fully data driven and nonergodic. We formulate ground-motion modeling as an image processing task, in which a specific type of neural network, the U-Net, relates continuous, horizontal maps of earthquake predictive parameters to sparse observations of a ground-motion intensity measure (IM). The processing of map-shaped data allows the natural incorporation of absolute earthquake source and observation site coordinates, and is, therefore, well suited to include site-, source-, and path-specific amplification effects in a nonergodic GMM. Data-driven interpolation of the IM between observation points is an inherent feature of the U-Net and requires no a priori assumptions. We evaluate our model using both a synthetic dataset and a subset of observations from the KiK-net strong motion network in the Kanto basin in Japan. We find that the U-Net model is capable of learning the magnitude–distance scaling, as well as site-, source-, and path-specific amplification effects from a strong motion dataset. The interpolation scheme is evaluated using a fivefold cross validation and is found to provide on average unbiased predictions. The magnitude–distance scaling as well as the site amplification of response spectral acceleration at a period of 1 s obtained for the Kanto basin are comparable to previous regional studies.

Description: Understanding fracturing processes and the hydromechanical relation to induced seismicity is a key question for enhanced geothermal systems (EGS). Commonly massive fluid injection, predominately causing hydroshearing, are used in large-scale EGS but also hydraulic fracturing approaches were discussed. To evaluate the applicability of hydraulic fracturing techniques in EGS, six in situ, multistage hydraulic fracturing experiments with three different injection schemes were performed under controlled conditions in crystalline rock at the A¨ spo¨ Hard Rock Laboratory (Sweden). During the experiments the near-field ground motion was continuously recorded by 11 piezoelectric borehole sensors with a sampling rate of 1 MHz. The sensor network covered a volume of 30×30×30 m around a horizontal, 28-m-long injection borehole at a depth of 410 m. To extract and characterize massive, induced, high-frequency acoustic emission (AE) activity from continuous recordings, a semi-automated workflow was developed relying on full waveform based detection, classification and location procedures. The approach extended the AE catalogue from 196 triggered events in previous studies to more than 19 600 located AEs. The enhanced catalogue, for the first time, allows a detailed analysis of induced seismicity during single hydraulic fracturing experiments, including the individual fracturing stages and the comparison between injection schemes. Beside the detailed study of the spatio-temporal patterns, event clusters and the growth of seismic clouds, we estimate relative magnitudes and b-values of AEs for conventional, cyclic progressive and dynamic pulse injection schemes, the latter two being fatigue hydraulic fracturing techniques. While the conventional fracturing leads to AE patterns clustered in planar regions, indicating the generation of a single main fracture plane, the cyclic progressive injection scheme results in a more diffuse, cloud-like AE distribution, indicating the activation of a more complex fracture network. For a given amount of hydraulic energy (pressure multiplied by injected volume) pumped into the system, the cyclic progressive scheme is characterized by a lower rate of seismicity, lower maximum magnitudes and significantly larger b-values, implying an increased number of small events relative to the large ones. To our knowledge, this is the first direct comparison of high resolution seismicity in a mine-scale experiment induced by different hydraulic fracturing schemes.

Description: The branch of seismology that deals with strong motion refers to seismic events that are hazardous to society in general.Two aspects drive the development in strong-motion seismology: First comes the societal need to understand the earth-quake hazard and to mitigate the associated risk. While the hazard changed little during human history, the risk in-creases steadily. A growing population—also in the most earthquake-prone regions of the world—and a more and morevulnerable infrastructure contribute to higher exposure to seismic events and higher vulnerability in case an earthquakestruck. The second driver in strong-motion seismology is shared with many other fields: the technological advancement.The available options for processing more and more data is unprecedented in human history and are still not exhausted.Both drivers also pose new challenges as in how to interpret and make use of the data.The scientific question, on the other hand, is clear: What can we learn from the rupture process (the source of earth-quakes), Earth’s structure (the medium through which seismic wave travels), and their interactions (how does an earth-quake affect its surrounding medium)? The question is broad and this thesis can focus only for specific aspects of thisquestion and provide answers for them. To reach the answers, I developed several new algorithms and models, all rootedin the concept of the likelihood function.Seismicity (and population alike) is concentrated along the tectonic plate boundaries. Different earthquake typesoccur at these boundaries and their characteristics in terms of ground shaking are considerably different. It is thereforeimportant to classify earthquakes according to their style of faulting. This classification is the objective of ACE (angularclusterization with expectation-maximization). Founded on the geomechanical principles, ACE provides earthquakeclassifications which can be applied not only for ground-motion related topics but also to study the Earth’s stress field.The development of reliable ground-motion models requires waveform data of high quality. Instrument related errorscan compromise the data quality, however, with large archives of waveform data, the correction for spurious s cannot behandled manually anymore. To alleviate the effect of instrument related data shifts, I developed the integrated combinedbaseline modification (ICBM). This routine is implemented during the data pre-processing and is particularly necessarywhen determining integrated quantities from acceleration records, such as coseismic displacement and radiated seismicenergy.Radiated seismic energy plays a major role in the development of a new type of ground-motion model that uses thesite-dependent energy estimates to model the seismic radiation pattern at lower frequencies of the earthquake amplitudespectrum. This kind of ground-motion model performs better when relating ground motion to earthquake triggeredlandslides, which is demonstrated with the landslides triggered by the 2016MW7.1 Kumamoto earthquake which struckcentral Kyushu (Japan). In this case study, it is also shown that the landslide movement direction is to some extent linkedto the seismic wave polarization.The preferred mathematical model in ground-motion model development is the mixed-effect model. However, themost widely used formalism does not allow data weighting beyond directly related measurement errors and weightsderived from ACE would inadvertently bias the model. To overcome this problem, I derived the model estimators onthe basis of the weighted likelihood. The derivation is exhaustive to allow for any of the currently used model types onthe basis of mixed effects to be augmented with data weighting. This formalism in connection with ACE allows for atransparent model development and also avoids model choices on subjective expert judgment

Description: Der Teil der Seismologie, der sich mit starker Bodenbewegung beschäftigt, bezieht sich auf seismische Ereignisse, dieallgemein ein Gefahrenpotenzial für die Gesellschaft darstellen. Die Seismologie der starken Bodenbewegung wird vonzwei Aspekten angetrieben: An erster Stelle kommt die gesellschaftliche Notwendigkeit, die Erdbebengefährdung zuverstehen und das damit verbundene Risiko zu vermeiden. Während die Gefährdung durch Erdbeben kaum Änderun-gen in der Geschichte der Menschheit unterlag, so wächst das Risiko andererseits kontinuierlich an. Eine wachsendeBevölkerung, insbesondere in den am stärksten von Erdbeben geprägten Regionen der Welt, und eine mehr und mehrstörungsanfällige Infrastruktur, tragen dazu bei, seismische Ereignissen vermehrt ausgesetzt zu sein, bei gleichzeitighöherem Schadenspotenzial. Der zweite Antrieb in der Seismologie wird mit vielen anderen Forschungsfeldern geteilt:der technische Fortschritt. Die verfügbaren Möglichkeiten beim Verarbeiten immer größerer Datenmengen sindbeispiellos in der Geschichte und sind bisher noch nicht erschöpft. Beide Triebfedern stellen aber auch neue Heraus-forderungen dar, inwiefern die Daten zu interpretieren sind und wie man sie nutzbar macht.Andererseits ist die wissenschaftliche Frage klar: Was können wir aus Bruchprozessen (als Erdbebenursachen), demAuf bau der Erde (als Medium, durch welches sich die seismischen Wellen ausbreiten), sowie deren Interaktion (inwiefernbeeinflusst das Beben das umgebende Gesteinsmedium)? Diese Frage ist breit gestellt und diese Abhandlung kann sichletztlich nur auf einige Punkte beziehen und Antworten dazu liefern. Um Antworten zu finden, habe ich mehrere neueAlgorithmen und Modelle entwickelt, die allesamt auf dem Konzept der Likelihood-Funktion beruhen.Seismizität (sowie auch die Bevölkerung) ist stark an den Rändern der tektonischen Platten konzentriert. An denPlattenrändern treten verschiedene Erdbebentypen mit teils erheblich abweichenden Eigenschaften auf. Daher ist esvon Wichtigkeit, Erdbeben nach ihrem Verwerfungstyp zu klassifizieren. Das Ziel von ACE (angular clusterization withexpectation-maximization, zu dt. ungefähr Winkelgruppenbestimmung mit Erwartungswertmaximierung) ist genaudiese Klassifizierung. Auf geomechanischen Prinzipien basierend, können die Erdbebenklassifizierungen mittels ACEnicht nur auf Themen der Bodenbewegungen angewandt werden, sondern auch zur Untersuchung des Spannungsfeldesder Erde herangezogen werden.Der Entwicklung von verlässlichen Bodenbewegungsmodellen bedarf es Wellenformdaten hoher Güte. Instrumentenbezogene Fehler können die Qualität beeinträchtigen, jedoch ist eine manuelle Korrektur großer Datenmengen nichtmehr umsetzbar. Um Instrumentenfehler, die sich in Verschiebungen in den Daten zeigen, zu reduzieren, habe icheine Nulllinienkorrektur entwickelt (ICBM, integrated combined baseline modification, zu dt. integriert kombinierteNulllinienmodifikation). Dieser Algorithmus wird in der Datenvorbereitung eingesetzt und ist insbesondere dannnotwendig, wenn integrierte Größen auf Grundlage von Beschleunigungsdaten bestimmt werden, wie statischer Ver-satz eines Erdbebens als auch abgestrahlte seismische Energie.Abgestrahlte seismische Energie spielt eine herausragende Rolle in der Entwicklung einer neuen Art von Bodenbewe-gungsmodell, welches anstellen von Magnituden stationsabhängige Energieabschätzungen nutzt, um die Erdbebenab-strahlcharakteristik auf tieferen Frequenzen des Erdbebenspektrums zu beschreiben. Diese Art Bodenbewegungsmodellist besser geeignet, wenn Bodenbewegungen in Bezug zu Hangrutschungen, welche durch Erdbeben verursacht wur-den, gesetzt werden. Als Beispiel dienen hier die Hangrutschungen, die 2016 durch das Erdbeben in Zentralkyuschu(Japan) mit einer Momentenmagnitude von 7.1 verursacht wurden. In dieser Fallstudie wird auch aufgezeigt, wie dieBewegungsrichtung der Hangrutschungen zu einem gewissen Grad durch die Ausrichtung des seismischen Wellenfeldesbeeinflusst werden.Das bevorzugte mathematische Modell in der Seismologie zur Beschreibung starker Bodenbewegungen ist das gemis-chte Modell. Jedoch lässt der weitläufig angewendete Formalismus nur die Einbettung von Gewichten in Form vonMessunsicherheiten zu. Gewichte wie sie von ACE erzeugt werden, die in keinem direkten Bezug zur Messgröße stehen,liefern zwangsläufig verzerrte Ergebnisse. Um dieses Problem zu umgehen, habe ich Parameterschätzer auf Basis einergewichteten Likelihood hergeleitet. Die rigorose Herleitung erlaubt sämtliche Arten des gemischten Modells, wie siezur Beschreibung von Bodenbewegungen genutzt werde, mit Datengewichtungen zu kombinieren. Dieser Formalis-mus in Verbindung mit ACE erlaubt die Entwicklung nachvollziehbarer Modelle und vermeidet Entscheidungen aufsubjektiver Expertenmeinung.

Description: We investigate the relation between frictional heating on a fault and the resulting conductive surface heat flow anomaly using the fault's long-term energy budget. Analysis of the surface heat flow surrounding the fault trace leads to a constraint on the frictional power generated on the fault—the mechanism behind the San Andreas fault (SAF) heat flow paradox. We revisit this paradox from a new perspective using an estimate of the long-term accumulating elastic power in the region surrounding the fault, and analyze the paradox using two parameters: the seismic efficiency and the elastic power. The results show that the constraint on frictional power from the classic interpretation is incompatible with the accumulating elastic power and the radiated power from earthquake catalogs. We then explore four mechanisms that can resolve this extended paradox. First, stochastic fluctuations of surface heat flow could mask the fault-generated anomaly (we estimate 21% probability). Second, the elastic power accumulating in the region could be overestimated (≥550 MW required). Third, the seismic efficiency—ratio of radiated energy to elastic work—of the SAF could be higher than that of the remaining faults in the region (≥5.8% required). Fourth, the scaled energy—ratio of radiated energy to seismic moment—on the SAF could be lower than on the remaining faults in the region (a factor 5 difference required). In the last three hypotheses, we analyze the interplay of the energy budget on a single fault with the total energy budget of the region.

Description: The selection of earthquake focal mechanisms (FMs) for stress tensor inversion (STI) is commonly done on a spatial basis, that is, hypocentres. However, this selection approach may include data that are undesired, for example, by mixing events that are caused by different stress tensors when for the STI a single stress tensor is assumed. Due to the significant increase of FM data in the past decades, objective data-driven data selection is feasible, allowing more refined FM catalogues that avoid these issues and provide data weights for the STI routines. We present the application of angular classification with expectation-maximization (ACE) as a tool for data selection. ACE identifies clusters of FM without a priori information. The identified clusters can be used for the classification of the style-of-faulting and as weights of the FM data. We demonstrate that ACE effectively selects data that can be associated with a single stress tensor. Two application examples are given for weighted STI from South America. We use the resulting clusters and weights as a priori information for an STI for these regions and show that uncertainties of the stress tensor estimates are reduced significantly.

Description: Rapid assessment of an earthquake’s impact on the affected society is a crucial step in the early phase of disaster management, navigating the need for further emergency response measures. We demonstrate that felt reports collected via the LastQuake service of the European Mediterranean Seismological Center can be utilized to rapidly estimate the probability of a felt earthquake being high impact rather than low impact on a global scale. Our data-driven, transparent, and reproducible method utilizing Bayes’ theorem and kernel density estimation provides results within 10 min for 393 felt events in 2021. Although a separation of high- and low-impact events remains challenging, the cor- rect and unambiguous assessment of a large portion of low-impact events is a key strength of our approach. We consider our method as an inexpensive addition to the pool of earthquake impact assessment tools, one that is fully independent of seismic data and can be utilized in many populated areas on the planet. Although practical deployment of our method remains an open task, we demonstrate the potential to improve disaster management in regions that currently lack expensive seismic instrumentation.

Description: Accelerograms are the primary source for characterizing strong ground motion. It is therefore of paramount interest to have high‐quality recordings free from any nonphysical contamination. Frequently, accelerograms are affected by baseline jumps and drifts, either related to the instrument and/or a major earthquake. In this work, I propose a correction method for these undesired baseline drifts based on segmented linear least squares. The algorithm operates on the integrated waveforms and combines all three instrument components to estimate a model that modifies the baseline to be at zero continuously. The procedure consists of two steps: first a suite of models with variable numbers of discontinuities is derived for all three instrument components. During this process, the number of discontinuities is reduced in a parsimonious way, for example, two very close discontinuities are merged into a single one. In the second step, the optimal model is selected on the basis of the Bayesian information criterion. I exemplify the application on synthetic waveforms with known discontinuities and on observed waveforms from a unified strong‐motion database of the Japan Meteorological Agency (JMA) and the National Research Institute for Earth Science and Disaster Prevention (NIED, Japan) networks for the major events of the 2016 Kumamoto earthquakes. After the baseline jump correction, the waveforms are furthermore corrected for displacement according to Wang et al. (2011). The resulting displacements are comparable to the Interferometric Synthetic Aperture Radar‐derived displacement estimates for the Kumamoto earthquake sequence.

Description: Ground motion with strong‐velocity pulses can cause significant damage to buildings and structures at certain periods; hence, knowing the period and velocity amplitude of such pulses is critical for earthquake structural engineering. However, the physical factors relating the scaling of pulse periods with magnitude are poorly understood. In this study, we investigate moderate but damaging earthquakes (⁠Mw 6–7) and characterize ground‐motion pulses using the method of Shahi and Baker (2014) while considering the potential static‐offset effects. We confirm that the within‐event variability of the pulses is large. The identified pulses in this study are mostly from strike‐slip‐like earthquakes. We further perform simulations using the frequency–wavenumber algorithm to investigate the causes of the variability of the pulse periods within and between events for moderate strike‐slip earthquakes. We test the effect of fault dips, and the impact of the asperity locations and sizes. The simulations reveal that the asperity properties have a high impact on the pulse periods and amplitudes at nearby stations. Our results emphasize the importance of asperity characteristics, in addition to earthquake magnitudes for the occurrence and properties of pulses produced by the forward directivity effect. We finally quantify and discuss within‐ and between‐event variabilities of pulse properties at short distances.

Description: The steady increase of ground-motion data not only allows new possibilities but also comes with new challenges in the development of ground-motion models (GMMs). Data classification techniques (e.g., cluster analysis) do not only produce deterministic classifications but also probabilistic classifications (e.g., probabilities for each datum to belong to a given class or cluster). One challenge is the integration of such continuous classification in regressions for GMM development such as the widely used mixed-effects model. We address this issue by introducing an extension of the mixed-effects model to incorporate data weighting. The parameter estimation of the mixed-effects model, that is, fixed-effects coefficients of the GMMs and the random-effects variances, are based on the weighted likelihood function, which also provides analytic uncertainty estimates. The data weighting permits for earthquake classification beyond the classical, expert-driven, binary classification based, for example, on event depth, distance to trench, style of faulting, and fault dip angle. We apply Angular Classification with Expectation–maximization, an algorithm to identify clusters of nodal planes from focal mechanisms to differentiate between, for example, interface- and intraslab-type events. Classification is continuous, that is, no event belongs completely to one class, which is taken into account in the ground-motionmodeling. The theoretical framework described in this article allows for a fully automatic calibration of ground-motionmodels using large databases with automated classification and processing of earthquake and ground-motion data. As an example, we developed a GMM on the basis of the GMM by Montalva et al. (2017) with data from the strong-motion flat file of Bastías and Montalva (2016) with ∼2400 records from 319 events in the Chilean subduction zone. Our GMMwith the data-driven classification is comparable to the expert-classification-based model. Furthermore, the model shows temporal variations of the between-event residuals before and after large earthquakes in the region.

Description: Surface heat flow is a geophysical variable that is affected by a complex combination of various heat generation and transport processes. The processes act on different lengths scales, from tens of meters to hundreds of kilometers. In general, it is not possible to resolve all processes due to a lack of data or modeling resources, and hence the heat flow data within a region is subject to residual fluctuations. We introduce the REgional HEAT-Flow Uncertainty and aNomaly Quantification (REHEATFUNQ) model, version 2.0.1. At its core, REHEATFUNQ uses a stochastic model for heat flow within a region, considering the aggregate heat flow to be generated by a gamma-distributed random variable. Based on this assumption, REHEATFUNQ uses Bayesian inference to (i) quantify the regional aggregate heat flow distribution (RAHFD) and (ii) estimate the strength of a given heat flow anomaly, for instance as generated by a tectonically active fault. The inference uses a prior distribution conjugate to the gamma distribution for the RAHFDs, and we compute parameters for a uninformed prior distribution from the global heat flow database by Lucazeau (2019). Through the Bayesian inference, our model is the first of its kind to consistently account for the variability in regional heat flow in the inference of spatial signals in heat flow data. Interpretation of these spatial signals and in particular their interpretation in terms of fault characteristics (particularly fault strength) form a long-standing debate within the geophysical community. We describe the components of REHEATFUNQ and perform a series of goodness-of-fit tests and synthetic resilience analyses of the model. While our analysis reveals to some degree a misfit of our idealized empirical model with real-world heat flow, it simultaneously confirms the robustness of REHEATFUNQ to these model simplifications. We conclude with an application of REHEATFUNQ to the San Andreas fault in California. Our analysis finds heat flow data in the Mojave section to be sufficient for an analysis and concludes that stochastic variability can allow for a surprisingly large fault-generated heat flow anomaly to be compatible with the data. This indicates that heat flow alone may not be a suitable quantity to address fault strength of the San Andreas fault.