ALBERT

Description: This study introduces a new approach for in situ Rb–Sr dating that utilizes rapid line scans instead of static spot ablation, enabling the creation of two-dimensional 87Rb/86Sr and 87Sr/86Sr isotope ratio and Rb–Sr age maps. The data acquisition is conducted utilizing an ICP-MS/MS instrument with N2O as the reaction gas, coupled to a 193 nm excimer laser via a low-aerosol-dispersion interface. This configuration allows for high repetition rates (〉100 Hz) and sensitivities, enabling data acquisition at a high scanning speed and small laser beam size (3–4 μm). Notably, this approach requires just about 1/30 of the sample volume typically utilized in conventional spot ablation mode, while achieving similar levels of precision and accuracy. Line scan ablation is tested and compared to spot ablation on age-homogeneous crystalline muscovite and biotite, for which reference Rb–Sr age data is acquired through ID-TIMS. Results show that a key requirement for accurate Rb–Sr ages based on line scan analyses is matrix correction using chemically matched crystalline mica. By presenting Rb–Sr age maps of three naturally deformed mica samples, we highlight the potential of Rb–Sr mapping for extracting age data from rocks that exhibit complex metamorphic-metasomatic histories and microscale dynamic recrystallization. Additionally, we show that quantitative elemental information (Al, Fe, Si, Li) can be collected alongside Rb–Sr isotope data. This advancement offers a distinctly more insightful assessment of isotope mobility in natural systems, the timing of element enrichment processes and enables, in high-Rb/Sr rock systems, precise and accurate isotopic dating of intricate geological processes at small scales.

Description: Correction to: Rock Mechanics and Rock Engineering https://doi.org/10.1007/s00603-023-03714-4 In the original publication, the “Funding Information” and “Acknowledgements” were mistakenly swapped.

Description: With the ongoing deployment of Global Navigation Satellite Systems (GNSS) ground stations and the modernization of satellite signal systems, the utilization of various augmentation technologies enables the realization of Precise Point Positioning (PPP) in real-time. Augmentation technology, which introduces precise atmospheric and signal-related delays, has become an essential component of high-precision real-time services and is attracting growing interest in scientific research, disaster monitoring, autopilot, etc. Previous studies have dedicated significant efforts to enhance the generation and dissemination of augmentation information on the service side and improve real-time positioning algorithms on the user side. The real-time atmosphere augmentation information with sufficient accuracy and proper constraint, and reliable Ambiguity Resolution (AR) for this purpose is the main focus of current GNSS research. However, these efforts have primarily been concentrated on small or medium-sized regions with the capability for transmitting massive data volumes. Alternatively, they have focused on larger areas, but with slow convergence due to the imprecise nature of atmosphere information. To address the challenge posed by the trade-offs among service area size, correction volume, and the precision of represented correction, a new augmentation strategy is proposed. This approach integrates the advantages of atmospheric delay fitting models, unmodeled residuals, and uncertainty information to achieve rapid and high-precision positioning, all while reducing data transmission volume for larger areas. It also allows users to implement different positioning modes depending on their communication capacity. Additionally, all deviations among different types of receivers and satellite signals are calibrated in this study for reliable AR can be achieved on all reference stations. The main contribution of this thesis is summarized as follows. With the real-time precise orbit, clock, and Uncalibrated Phase Delay (UPD) products, precise atmospheric delay corrections relying on reliable AR can be derived for large-areas augmentation services. To address the challenge of achieving reliable AR across different receiver types and various satellite signals, this thesis proposes a comprehensive method for calibrating receiver-type-related satellite-specific deviations and analyzes the impact of satellite signal bias corrections in data processing. The primary objective is to enhance the reliability of AR, enabling the utilization of all available signals and receiver types in large-area services. Subsequently, new tropospheric and ionospheric delay fitting models applied for large-area are carried out according to the properties of their propagation paths. In addition, the corresponding atmospheric delay uncertainty for large areas is introduced based on the fitting residuals. Finally, a hierarchical mode is developed for augmentation services, leveraging the advantages of the fitting model and uncertainty grid to reduce data volume and incorporating regional fitting residuals using the interpolation model and ionospheric delay error function, depending on the network capability. Based on hierarchical augmentation, positioning in large areas can not only achieve rapid/instantaneous high-precision convergence but also overcome the conflict among correction volume, represented precision, and coverage size. In order to derive precise atmospheric delay and accelerate positioning, implementing reliable and robust AR across all types of receivers and satellite signals is essential. It also demonstrates and discusses the advantages of calibrating satellite-signal and receiver-type-related satellite-specific deviations in AR solutions. The deviations related to receivers in terms of UPD products are assessed and calibrated, confirming that a 0.03 cycle consistency in wide lane UPD can be achieved. The effectiveness of the proposed approach is demonstrated using GPS satellite signals, which can improve the AR rate by at least 10% and produce more reliable results. In addition, the impact of different signal settings and corrections on orbit, clock, and UPD generation, as well as positioning and pseudo-range signal systematic and stochastic residuals, is analyzed. These processing strategies provide flexible observation selections, allowing the utilization of all available satellite signals and receiver types, thereby enabling reliable AR and a higher fixing rate. As a result, an AR fixing rate exceeding 95% is achievable across all stations in large-area services. For precise atmospheric delay modeling over large areas, new models are proposed, including a tropospheric Zenith Wet Delay (ZWD) model and a satellite-wise ionospheric slant delay fitting model. The tropospheric delay model takes the exponential function of water vapor vertical changes into consideration, addressing model anomalies in areas with large altitude differences. The new ionospheric delay fitting model introduces the trigonometric functions to describe differences in slant path delays between the optimal reference propagation path and others, achieving superior modeling performance in large areas. The precision of the fitting model, utilizing a 200 km station-spacing network, demonstrates tropospheric ZWD and ionospheric slant delays of 1.3 cm and 8.9 cm, respectively, with smaller standard deviations. These new fitting models overcome the challenge of handling massive information for providing station-wise corrections and avoid an increase in the number of coefficients. In addition to the function model, the stochastic model, i.e., uncertainty information, is essential for describing the quality of corrections. The atmospheric delay uncertainty for the large-area fitting model is generated based on the fitting residuals and represented in forms of grid-point. Additionally, regional ionosphere unmodeled residual uncertainty is represented by the form of liner function, which is established by the relationship between distance and interpolation precision through inter-satellite cross-verification among all reference stations. The differences between uncertainty value and real delays are 2.5 cm and 0.5 cm for grid and function forms, respectively. For real-time applications in large areas, the fitting model and grid-based atmosphere uncertainty serve as the essential information, satisfying the requirement of rapid positioning. By further incorporating unmodeled residuals and ionosphere error function, a hierarchical augmentation model is provided. Based on the fitting model established for large areas, unmodeled residuals are further introduced as optional compensation for specific areas, depending on the magnitude of fitting residuals. This approach results in a 97% reduction in tropospheric delay and a 65% reduction in ionospheric delay transmission volume. Furthermore, leveraging the regional high capability of communication, 85.3% of all solutions can achieve instantaneous convergence at the first epoch with the aid of corresponding regional compensation. This thesis proposes a large areas augmentation service to overcome the conflict among correction data volume, represented precision, and coverage size. It demonstrates the benefits of an augmentation mode that integrates regional information into large-area services. Under these conditions, a more reliable and rapid AR solution can be easily achieved based on precise atmospheric delay correction and uncertainty in large areas with fewer data volume requirements. This is beneficial for actual real-time services and applications.

Description: Mit der laufenden Bereitstellung von Bodenstationen für globale Navigationssatellitensysteme (GNSS) und der Modernisierung von Satellitensignal-Systemen ermöglicht die Nutzung verschiedener Augmentationstechnologien die Realisierung der Präzisen Punkt-Positionierung (PPP) in Echtzeit. Augmentationstechnologie, die präzise atmosphärische und signalbezogene Verzögerungen einführt, ist zu einem wesentlichen Bestandteil hochpräziser Echtzeitdienste geworden und findet wachsendes Interesse in wissenschaftlicher Forschung, Katastrophenüberwachung, Autopiloten usw. Frühere Studien haben erhebliche Anstrengungen darauf verwendet, die Erzeugung und Verbreitung von Augmentationsinformationen auf der Dienstseite zu verbessern und Echtzeit-Positionierungsalgorithmen auf der Benutzerseite zu optimieren. Die Echtzeit-Atmosphärenaugmentationsinformationen mit ausreichender Genauigkeit und angemessener Einschränkung sowie zuverlässige Ambiguitätsauflösung (AR) für diesen Zweck stehen im Mittelpunkt der aktuellen GNSS-Forschung. Diese Bemühungen konzentrierten sich jedoch hauptsächlich auf kleine oder mittelgroße Regionen mit der Fähigkeit zur Übertragung großer Datenmengen. Alternativ richteten sie sich auf größere Gebiete, jedoch mit langsamer Konvergenz aufgrund der ungenauen Natur der Atmosphäreninformation. Um der Herausforderung durch die Abwägung zwischen Größe des Dienstleistungsgebiets, Korrekturvolumen und Präzision der dargestellten Korrektur zu begegnen, wird eine neue Augmentationsstrategie vorgeschlagen. Dieser Ansatz integriert die Vorteile atmosphärischer Verzögerungsanpassungsmodelle, nicht modellierter Reste und Unsicherheitsinformationen, um eine schnelle und hochpräzise Positionierung zu erreichen, und das bei gleichzeitiger Reduzierung der Datenübertragungsvolumina für größere Gebiete. Es ermöglicht den Benutzern auch, verschiedene Positionierungsmodi je nach ihrer Kommunikationskapazität zu implementieren. Zusätzlich werden in dieser Studie alle Abweichungen zwischen verschiedenen Typen von Empfängern und Satellitensignalen kalibriert, um eine zuverlässige AR an allen Referenzstationen zu erreichen. Die Hauptbeiträge dieser Arbeit werden wie folgt zusammengefasst. Mit den Echtzeit-Präzbitbahnen, Uhren und Uncalibrated Phase Delay (UPD)-Produkten können präzise atmosphärische Verzögerungskorrekturen für großflächige Augmentationsdienste abgeleitet werden, die auf zuverlässiger AR basieren. Um die Herausforderung zu bewältigen, eine zuverlässige AR über verschiedene Empfängertypen und verschiedene Satellitensignale hinweg zu erreichen, schlägt diese Arbeit eine umfassende Methode zur Kalibrierung von empfängertypbezogenen satellspezifischen Abweichungen vor und analysiert die Auswirkungen von Korrekturen für Satellitensignalverzerrungen in der Datenverarbeitung. Das Hauptziel besteht darin, die Zuverlässigkeit der AR zu verbessern und die Nutzung aller verfügbaren Signale und Empfängertypen in großflächigen Diensten zu ermöglichen. Anschließend werden neue troposphärische und ionosphärische Verzögerungsanpassungsmodelle für großflächige Anwendungen gemäß den Eigenschaften ihrer Ausbreitungspfade durchgeführt. Darüber hinaus wird die entsprechende atmosphärische Verzögerungsunsicherheit für große Gebiete auf der Grundlage der Anpassungsreste eingeführt. Schließlich wird ein hierarchischer Modus für Augmentationsdienste entwickelt, der die Vorteile des Anpassungsmodells und des Unsicherheitsgitters nutzt, um das Datenvolumen zu reduzieren und regionale Anpassungsreste unter Verwendung des Interpolationsmodells und der ionosphärischen Verzögerungsfehlerfunktion, abhängig von der Netzwerkfähigkeit, zu integrieren. Basierend auf der hierarchischen Augmentation kann die Positionierung in großen Gebieten nicht nur eine schnelle/instantane hochpräzise Konvergenz erreichen, sondern auch den Konflikt zwischen Korrekturvolumen, dargestellter Präzision und Abdeckungsgröße überwinden. Um präzise atmosphärische Verzögerungen abzuleiten und die Positionierung zu beschleunigen, ist es entscheidend, eine zuverlässige und robuste AR über alle Arten von Empfängern und Satellitensignalen zu implementieren. Es zeigt auch die Vorteile der Kalibrierung von satellitensignal- und empfängertypbezogenen satellspezifischen Abweichungen in AR-Lösungen auf. Die Abweichungen im Zusammenhang mit Empfängern in Bezug auf UPD-Produkte werden bewertet und kalibriert, wobei bestätigt wird, dass eine Konsistenz von 0,03 Zyklen bei Wide-Lane-UPD erreicht werden kann. Die Wirksamkeit des vorgeschlagenen Ansatzes wird unter Verwendung von GPS-Satellitensignalen demonstriert, die die AR-Rate um mindestens 10% verbessern und zu zuverlässigeren Ergebnissen führen können. Darüber hinaus wird der Einfluss unterschiedlicher Signalparameter und Korrekturen auf die Erzeugung von Orbit, Uhr und UPD sowie auf die Positionierung und systematische und stochastische Reste der Pseudo-Range-Signale analysiert. Diese Verarbeitungsstrategien bieten flexible Auswahlmöglichkeiten bei der Beobachtung und ermöglichen die Nutzung aller verfügbaren Satellitensignale und Empfängertypen, wodurch eine zuverlässige AR und eine höhere Fixierungsrate ermöglicht wird. Als Ergebnis ist eine AR-Fixierungsrate von über 95% bei allen Stationen in großflächigen Diensten erreichbar. Für eine präzise Modellierung atmosphärischer Verzögerungen über großen Gebieten werden neue Modelle vorgeschlagen, darunter ein troposphärisches Zenith Wet Delay (ZWD)-Modell und ein satellitenweises ionosphärisches Schrägverzögerungsanpassungsmodell. Das troposphärische Verzögerungsmodell berücksichtigt die exponentielle Funktion der vertikalen Änderungen des Wasserdampfs und behebt Modellanomalien in Gebieten mit großen Höhendifferenzen. Das neue ionosphärische Verzögerungsanpassungsmodell verwendet trigonometrische Funktionen, um Unterschiede in den Schrägpfadverzögerungen zwischen dem optimalen Referenzausbreitungspfad und anderen zu beschreiben und erreicht so eine überlegene Modellierungsleistung in großen Gebieten. Die Präzision des Anpassungsmodells, unter Verwendung eines 200 km-Stationen-Netzwerks, zeigt troposphärische ZWD- und ionosphärische Schrägverzögerungen von jeweils 1,3 cm und 8,9 cm mit kleineren Standardabweichungen. Diese neuen Anpassungsmodelle überwinden die Herausforderung, massive Informationen für die Bereitstellung stationsspezifischer Korrekturen zu verarbeiten, und vermeiden eine Zunahme der Anzahl der Koeffizienten. Neben dem Funktionsmodell ist das stochastische Modell, d. h. Unsicherheitsinformationen, entscheidend für die Beschreibung der Qualität der Korrekturen. Die Unsicherheit der atmosphärischen Verzögerung für das großflächige Anpassungsmodell wird auf der Grundlage der Anpassungsreste generiert und in Form von Gitterpunkten dargestellt. Zusätzlich wird die regionale ionosphärische nicht modellierte Restunsicherheit durch die Form einer linearen Funktion repräsentiert, die durch die Beziehung zwischen Entfernung und Interpolationsgenauigkeit durch inter-satellitenkreuz-Verifikation zwischen allen Referenzstationen etabliert wird. Die Unterschiede zwischen Unsicherheitswert und realen Verzögerungen betragen 2,5 cm bzw. 0,5 cm für Gitter- und Funktionsformen. Für Echtzeitanwendungen in großen Gebieten dienen das Anpassungsmodell und die gitterbasierte Atmosphärenunsicherheit als wesentliche Informationen, die die Anforderungen an schnelle Positionierung erfüllen. Durch die weitere Integration von nicht modellierten Resten und Ionosphärenfehlerfunktion wird ein hierarchisches Augmentationsmodell bereitgestellt. Basierend auf dem für große Gebiete etablierten Anpassungsmodell werden nicht modellierte Reste zusätzlich als optionale Kompensation für spezifische Bereiche eingeführt, abhängig von der Größenordnung der Anpassungsreste. Dieser Ansatz führt zu einer Reduktion von 97% der troposphärischen Verzögerung und einer Reduktion von 65% des ionosphärischen Verzögerungsvolumens. Darüber hinaus können unter Nutzung der regionalen hohen Kommunikationsfähigkeit 85,3% aller Lösungen mit Hilfe entsprechender regionaler Kompensation eine sofortige Konvergenz beim ersten Epochenzeitpunkt erreichen. Diese Dissertation schlägt einen großflächigen Augmentationsdienst vor, um den Konflikt zwischen Korrekturvolumen, dargestellter Präzision und Abdeckungsgröße zu überwinden. Sie zeigt die Vorteile eines Augmentationsmodus, der regionale Informationen in großflächige Dienste integriert. Unter diesen Bedingungen kann eine zuverlässigere und schnellere AR-Lösung basierend auf präziser atmosphärischer Verzögerungskorrektur und Unsicherheit in großen Gebieten mit geringeren Anforderungen an das Datenvolumen leicht erreicht werden. Dies ist vorteilhaft für tatsächliche Echtzeitdienste und Anwendungen.

Description: Trawl-fishing is broadly considered to be one of the most destructive anthropogenic activities toward benthic ecosystems. In this study, we examine the effects of bottom-contact fishing by otter trawls on the geochemistry and macrofauna in sandy silt sediment in an area of the Baltic Sea where clear spatial patterns in trawling activity were previously identified by acoustic mapping. We calibrated an early diagenetic model to biogeochemical data from various coring locations. Fitting measured mercury profiles allowed for the determination of the sediment mixing and burial velocity. For all sites, independent of the trawl mark density, good fits were obtained by applying the model with the same organic matter loading and parameter values, while iron fluxes scaled linearly with the burial velocity. A sensitivity analysis revealed that the fitted sulfate reduction rate, solid sulfur contents, ammonium concentration, and both the isotopic composition and concentration of dissolved inorganic carbon provided reliable constraints for the total mineralization rate, which exhibited a narrow range of variability (around ±20 % from the mean) across the sites. Also, the trawling intensity did not significantly correlate with total organic carbon contents in surficial sediment, indicating limited loss of organic matter due to trawling. The fits to the reactive iron, acid volatile sulfur, chromium(II) reducible sulfur contents, and porewater composition demonstrate that sediment burial and mixing primarily determine the redox stratification. The mixing depth did not correlate with trawling intensity and is more likely the result of bioturbation, as the analyzed macrofaunal taxonomy and density showed a high potential for sediment reworking. The extraordinarily long-lived Arctica islandica bivalve dominated the infaunal biomass, despite the expectation that trawling leads to the succession from longer-lived to shorter-lived and bigger to smaller macrofauna. Our results further suggest that a clear geochemical footprint of bottom-trawling may not develop in sediments actively reworked by tenacious macrofauna.

Description: Analyzing seismic data in a timely manner is essential for potential eruption forecasting and early warning in volcanology. Here, we demonstrate that unsupervised machine learning methods can automatically uncover hidden details from the continuous seismic signals recorded during Iceland’s 2021 Geldingadalir eruption. By pinpointing the eruption’s primary phases, including periods of unrest, ongoing lava extrusion, and varying lava fountaining intensities, we can effectively chart its temporal progress. We detect a volcanic tremor sequence three days before the eruption, which may signify impending eruptive activities. Moreover, the discerned seismicity patterns and their temporal changes offer insights into the shift from vigorous outflows to lava fountaining. Based on the extracted patterns of seismicity and their temporal variations we propose an explanation for this transition. We hypothesize that the emergence of episodic tremors in the seismic data in early May could be related to an increase in the discharge rate in late April.

Description: In modelling atmospheric loading effects for terrestrial gravimetry, state-of-the-art approaches take advantage of numerical weather models to account for the global 3-D distribution of air masses. Deformation effects are often computed assuming the Inverse Barometer (IB) hypothesis to be generally valid over the oceans. By a revision of the IB assumption and its consequences we show that although the seafloor is not deformed by atmospheric pressure changes, there exists a fraction of ocean mass that current modelling schemes are usually not accounting for. This causes an overestimation of the atmospheric attraction effect over oceans, even when the dynamic response of the ocean to atmospheric pressure and wind is accounted through dynamic ocean models. This signal can reach a root mean square variability of a few nm s−2, depending on the location of the station. We therefore test atmospheric and non-tidal ocean loading effects at five superconducting gravimeter (SG) stations, showing that a better representation of the residual gravity variations is found when Newtonian attraction effects due to the IB response of the ocean are correctly considered. A sliding window variance analysis shows that the main reduction takes place for periods between 5 and 10 d, even for stations far away from the oceans. Since periods of non-tidal ocean mass variability closely resemble atmospheric signals recorded by SGs, we recommend to directly incorporate both an ocean component together with the IB into services that provide weather-related corrections for terrestrial gravimetry.

Description: Ferropericlase (Mg,Fe)O is after bridgmanite the most abundant phase in the lower mantle. The ultralow velocity zones above the core-mantle boundary may contain very Fe-rich magnesiowüstite (Fe,Mg)O, possibly as result of the fractional crystallisation of a basal magma ocean. We have experimentally studied the solubility of nitrogen in the ferropericlase-magnesiowüstite solid solution series as function of iron content. Multi-anvil experiments were performed at 20–33 GPa and 1600–1800 °C in equilibrium with Fe metal. Nitrogen solubility increases from a few tens ppm (μg/g) for Mg-rich ferropericlase to more than 10 wt. % for nearly pure wüstite. Such high solubilities appear to be due to solid solution with NiAs-type FeN. Our data suggest that during fractional crystallisation of a magma ocean, the core-mantle boundary would have become extremely enriched with nitrogen, such that the deep mantle today could be the largest nitrogen reservoir on Earth. The often discussed “subchondritic N/C” ratio of the bulk silicate Earth may be an artefact of insufficient sampling of this deep reservoir.

Description: Assessing the potential and extent of earthquake-induced liquefaction is paramount for seismic hazard assessment, for the large ground deformations it causes can result in severe damage to infrastructure and pose a threat to human lives, as evidenced by many contemporary and historical case studies in various tectonic settings. In that regard, numerical modeling of case studies, using state-of-the-art soil constitutive models and numerical frameworks, has proven to be a tailored methodology for liquefaction assessment. Indeed, these simulations allow for the dynamic response of liquefiable soils in terms of effective stresses, large strains, and ground displacements to be captured in a consistent manner with experimental and in-situ observations. Additionally, the impact of soil properties spatial variability in liquefaction response can be assessed, because the system response to waves propagating are naturally incorporated within the model. Considering that, we highlight that the effect of shear-wave velocity Vs spatial variability has not been thoroughly assessed. In a case study in Metropolitan Concepción, Chile, our research addresses the influence of Vs spatial variability on the dynamic response to liquefaction. At the study site, the 2010 Maule Mw 8.8 megathrust Earthquake triggered liquefaction-induced damage in the form of ground cracking, soil ejecta, and building settlements. Using simulated 2D Vs profiles generated from real 1D profiles retrieved with ambient noise methods, along with a PressureDependentMultiYield03 sand constitutive model, we studied the effect of Vs spatial variability on pore pressure generation, vertical settlements, and shear and volumetric strains by performing effective stress site response analyses. Our findings indicate that increased Vs variability reduces the median settlements and strains for soil units that exhibit liquefaction-like responses. On the other hand, no significant changes in the dynamic response are observed in soil units that exhibit non-liquefaction behavior, implying that the triggering of liquefaction is not influenced by spatial variability in Vs. We infer that when liquefaction-like behavior is triggered, an increase of the damping at the shallowest part of the soil domain might be the explanation for the decrease in the amplitude of the strains and settlements as the degree of Vs variability increases.

Description: Public earthquake early warning systems (PEEWSs) have the potential to save lives by warning people of incoming seismic waves up to tens of seconds in advance. Given the scale and geographical extent of their impact, this potential is greatest for destructive earthquakes, such as the M7.8 Pazarcik (Türkiye) event of 6 February 2023, which killed almost 60,000 people. However, warning people of imminent strong shaking is particularly difficult for large-magnitude earthquakes because the warning must be given before the earthquake has reached its final size. Here, we show that the Earthquake Network (EQN), the first operational smartphone-based PEEWS and apparently the only one operating during this earthquake, issued a cross-border alert within 12 s of the beginning of the rupture. A comparison with accelerometer and macroseismic data reveals that, owing to the EQN alerting strategy, Turkish and Syrian EQN users exposed to intensity IX and above benefitted from a warning time of up to 58 s before the onset of strong ground shaking. If the alert had been extended to the entire population, approximately 2.7 million Turkish and Syrian people exposed to a lifethreatening earthquake would have received a warning ranging from 30 to 66 s in advance.

Description: The joint European Space Agency and Chinese Academy of Sciences Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission will explore global dynamics of the magnetosphere under varying solar wind and interplanetary magnetic field conditions, and simultaneously monitor the auroral response of the Northern Hemisphere ionosphere. Combining these large-scale responses with medium and fine-scale measurements at a variety of cadences by additional ground-based and space-based instruments will enable a much greater scientific impact beyond the original goals of the SMILE mission. Here, we describe current community efforts to prepare for SMILE, and the benefits and context various experiments that have explicitly expressed support for SMILE can offer. A dedicated group of international scientists representing many different experiment types and geographical locations, the Ground-based and Additional Science Working Group, is facilitating these efforts. Preparations include constructing an online SMILE Data Fusion Facility, the discussion of particular or special modes for experiments such as coherent and incoherent scatter radar, and the consideration of particular observing strategies and spacecraft conjunctions. We anticipate growing interest and community engagement with the SMILE mission, and we welcome novel ideas and insights from the solar-terrestrial community.

Description: Geothermal energy is one of the most viable sources of renewable heat. However, the potential risk of induced seismicity associated with geothermal operations may slow down the growth of the geothermal sector. Previous research has led to significant progress in understanding fluidinjection- induced seismicity in geothermal reservoirs. However, an in-depth assessment of thermal effects on the seismic risk was generally considered to be of secondary importance. This study aims to investigate the relative influence of temperature and key geological and operational parameters on the slip tendency of pre-existing faults. This is done through coupled thermo-hydro-mechanical simulations of the injection and production processes in synthetic geothermal reservoir models of the most utilized and potentially exploitable Dutch geothermal reservoir formations: Slochteren sandstone, Delft sandstone and Dinantian limestone. In our study, changes in the slip tendency of a fault can largely be attributed to thermo-elastic effects, which confirms the findings of recent studies linking thermal stresses to induced seismicity. While the direct pore pressure effect on slip tendency tends to dominate over the early phase of the operations, once pore pressure equilibrium is established in a doublet system, it is the additional stress change associated with the growing cold-water front around the injection well that has the greatest influence. Therefore, the most significant increase in the slip tendency was observed when this low-temperature front reached the fault zone. The distance between an injection well and a pre-existing fault thus plays a pivotal role in determining the mechanical stability of a fault. A careful selection of a suitable target formation together with an appropriate planning of the operational parameters is also crucial to mitigate the risk of induced seismicity. Besides the well-known relevance of the in situ stress field and local fault geometry, rock-mechanical properties and operation conditions exert a major influence on induced stress changes and therefore on the fault (re)activation potential during geothermal operations.

Description: The CNSC, the Canadian regulator for the nuclear industry, participated in DECOVALEX-2023 Task G that focuses on the thermo (T) - hydro (H)- mechanical (M) behaviour of rock joints. Joints are omnipresent in rock masses and are planes of weakness in the host rock. When deep geological repositories (DGRs) for radioactive waste are being considered in areas where rock joints are present, the joints could be preferential pathways for radionuclide migration. Therefore, their THM behaviour must be better understood to assess the safety of the DGR. Under different possible internal and external perturbations, a joint can move by shear and dilation. If the joint crosses the emplacement area of a waste container, the heat generated from the waste can itself induce shearing of the joint. Excessive shear movement can in turn lead to failure of the container, resulting in earlier release of radionuclides. Furthermore, dilation that might accompany shear, results in an increase in the joint aperture creating a faster flow path for radionuclide transport. Mathematical models are important tools that need to be developed and employed, in order to assess joint shear and dilation under different loading conditions, such as the heat generated from the emplaced waste. The authors have developed such a mathematical model based on a macroscopic formulation within the framework of elasto-plasticity. It is verified against analytical solutions and validated against shear under constant normal load tests and thermal shearing tests of joints in granite.

Description: Hydraulic fracturing has been widely used to enhance reservoir permeability during the extraction of shale gas. As one of the external input parameters, injection rate has a significant impact on formation breakdown pressure and the complexity of hydraulic fractures. To gain deeper insights into the effect of injection rate on breakdown pressure and fracture morphology, we conducted five hydraulic fracturing experiments on Changning shale in the laboratory. We used five different injection rates between 3 and 30 mL/min to fracture cylindrical core samples with 50 mm in diameter and 100 mm in length. We monitored acoustic emissions and surface displacements during the tests, and analyzed the fracture pattern post mortem by using a fluorescent tracer. We find a semi-logarithmic relationship between the breakdown pressure and the injection rates. Second, we find that it is the injection rate that dictates sample deformation and crack formation during breakdown rather than the fluid volume injected during the whole process. The analysis of amplitudes and frequency of acoustic signals indicates that hydraulic fracturing of Changning shale is overall dominated by tensile fractures (〉 60%). However, at low injection rates, shear events are facilitated before rock breakdown. On the other hand, high injection rates result in reducing fracture tortuosity and surface roughness due to limited fluid infiltration in the relatively short injection window. We close this study with a conceptual model to explain the difference between fluid infiltration (low injection rates) and the loading rate effect (high injection rate) in low-permeability shale rocks. The findings obtained in this study can help to adjust injection rates in the field to economically and safely produce gas from shale.

Description: Secondary ion mass spectrometry was used to test the d18O and d34S nanogram-scale homogeneity of a suite of candidate sulfate minerals, ultimately selecting three barite, two anhydrite, and two gypsum samples from the Royal Ontario Museum that have repeatabilities for their SIMS measurements of better than 0.39‰ and 0.37‰ (1s) for oxygen and sulfur isotope ratios, respectively. Metrological splits of each of the seven materials were sent to multiple gas source isotope ratio mass spectrometry laboratories in order to establish their absolute 18O/16O and 34S/32S ratios. The inter-laboratory results of GS-IRMS analyses yielded reasonably narrow ranges in d18OVSMOW, whereas larger variations in d34SVCDT values were found between the results from the gas source laboratories. All samples have good reproducibility within laboratories of GS-IRMS 103d18O values of between 0.24‰ and 0.44‰ (1s). The reproducibility within laboratories of GS-IRMS 103d34S values range from 0.07‰ to 0.99‰ (1s). Here we also discuss some of the current analytical limitations affecting these isotope-mineral systems. A total of 256 metrological splits have been prepared from each of these seven materials; these aliquots will be made available to the global geochemical community.

Description: The increasing demand for fertilizers and their rising prices has led to the search for new nutrient sources, especially in rural areas where family farming predominates. In this study, we assessed the potential of reusing sediment deposited in surface reservoirs as a soil conditioner in a semiarid region, focusing on two features: the characterization of sediment physicochemical properties at the regional scale and the effect of the substrate containing sediment on the growth and physiology of maize.

Description: The analysis of Coulomb stress changes has become an important tool for seismic hazard evaluation because such stress changes may trigger or delay subsequent earthquakes. Processes that can cause significant Coulomb stress changes include coseismic slip and transient postseismic processes such as poroelastic effects and viscoelastic relaxation. However, the combined influence of poroelastic effects and viscoelastic relaxation on co- and postseismic Coulomb stress changes has not been systematically studied so far. Here, we use three-dimensional finite-element models with arrays of normal and thrust faults to investigate how pore fluid pressure changes and viscoelastic relaxation overlap during the postseismic phase. In different experiments, we vary the permeability of the upper crust and the viscosity of the lower crust or lithospheric mantle while keeping the other parameters constant. In addition, we perform experiments in which we combine a high (low) permeability of the upper crust with a low (high) viscosity of the lower crust. Our results show that the coseismic (i.e., static) Coulomb stress changes are altered by the signal from poroelastic effects and viscoelastic relaxation during the first month after the earthquake. For sufficiently low viscosities, the Coulomb stress change patterns show a combined signal from poroelastic and viscoelastic effects already during the first postseismic year. For sufficiently low permeabilities, Coulomb stress changes induced by poroelastic effects overlap with the signals from viscoelastic relaxation and interseismic stress accumulation for decades. Our results imply that poroelastic and viscoelastic effects have a strong impact on postseismic Coulomb stress changes and should therefore be considered together when analyzing Coulomb stress transfer between faults.

Description: The impact of faults on the contemporary stress field in the upper crust has been discussed in various studies. Data and models clearly show that there is an effect, but so far, a systematic study quantifying the impact as a function of distance from the fault is lacking. In the absence of data, here we use a series of generic 3-D models to investigate which component of the stress tensor is affected at which distance from the fault. Our study concentrates on the far field, lo- cated hundreds of metres from the fault zone. The models assess various techniques to represent faults, different mate- rial properties, different boundary conditions, variable orien- tation, and the fault’s size. The study findings indicate that most of the factors tested do not have an influence on ei- ther the stress tensor orientation or principal stress magni- tudes in the far field beyond 1000 m from the fault. Only in the case of oblique faults with a low static friction coeffi- cient of μ = 0.1 can noteworthy stress perturbations be seen up to 2000 m from the fault. However, the changes that we detected are generally small and of the order of lateral stress variability due to rock property variability. Furthermore, only in the first hundreds of metres to the fault are variations large enough to be theoretically detected by borehole-based stress data when considering their inherent uncertainties. This find- ing agrees with robust stress magnitude measurements and stress orientation data. Thus, in areas where high-quality and high-resolution data show gradual and continuous stress ten- sor rotations of 〉 20◦ observed over lateral spatial scales of 10 km or more, we infer that these rotations cannot be at- tributed to faults. We hypothesize that most stress orienta- tion changes attributed to faults may originate from different sources such as density and strength contrasts.

Description: The Samail Ophiolite in the Oman Mountains formed at a Cretaceous subduction zone that was part of a wider Neo-Tethys plate-boundary system. The original configuration and evolution of this plate-boundary system is hidden in a structurally and metamorphically complex nappe stack below the Samail Ophiolite. Previous work provided evidence for high-temperature metamorphism high in the nappe pile (in the metamorphic sole of the Samail Ophiolite), and high-pressure metamorphism in the deepest part of the nappe pile (Saih Hatat window), possibly reflecting a downward younging, progressive accretion history at the Samail subduction zone. However, there is evidence that the two subduction-related metamorphic events are disparate, but temporally overlapping during the mid-Cretaceous. We present the first geochronologic dataset across the entire high-pressure nappe stack below the Samail Ophiolite, and the shear zones between the high-pressure nappes. Our 22 new Rbsingle bondSr multimineral isochron ages from the Saih Hatat window, along with independent new field mapping and kinematic reconstructions, constrain the timing and geometry of tectonometamorphic events. Our work indicates the existence of a high-pressure metamorphic event in the nappes below the ophiolite that was synchronous with the high-temperature conditions in the metamorphic sole. We argue that the thermal conditions of these synchronous metamorphic events can only be explained through the existence of two Cretaceous subduction zones/segments that underwent distinctly different thermal histories during subduction infancy. We infer that these two subduction zones initially formed at two perpendicular subduction segments at the Arabian margin and subsequently rotated relative to each other and, as a consequence, their records became juxtaposed: (1) The high-temperature metamorphic sole and the Samail Ophiolite both formed above the structurally higher, outboard, ‘hot’ and rotating Samail subduction zone and, (2) the high-pressure nappes developed within the structurally lower, inboard, ‘cold’ Ruwi subduction zone. We conclude that the formation and evolution of both subduction zones were likely controlled by the density structure of the mafic-rock-rich Arabian rifted margin and outermost Arabian Platform, and the subsequent arrival of the buoyant, largely mafic-rock-free, full-thickness Arabian lithosphere, which eventually halted subduction at the southern margin of Neo-Tethys. Previous article in issue

Description: This data set contains the results from a 2023 GFZ Innovative Research Expedition project to explore for natural hydrogen gas (H2) occurrences in the NW Pyrenean foreland, near the town of Biarritz in France. The data represent in-situ measurements of soil and spring water gas, as well as in-situ spring water property measurements, complemented with laboratory analysis results of gas contents and noble gas isotopic compositions of gas and spring water samples collected during the expedition. This GFZ Innovative Research Expedition was inspired by previous exploration efforts in the region by Lefeuvre et al. (2021, 2022). These authors detected elevated concentrations of natural H2 gas in the soil and interpreted this natural H2 to be derived from serpentinizing mantle rocks below the Pyrenees. The main aims of this expedition were the following: (1) in-situ measuring soil gas contents and taking soil gas samples for laboratory analysis at a site near the town of Peyrehorade in the NW of the general study area of Lefeuvre et al. (2021), thus improving the soil gas data coverage along the NW end of the North Pyrenean Frontal Thrust (NPFT); (2) taking gas samples from degassing springs (or water samples from non-degassing springs to be degassed in the lab) in the general Lefeuvre et al. (2021) study area for additional laboratory analysis of gas contents and noble gas isotopic compositions, which may be indicative of (deep) gas origins; and (3) performing a detailed soil gas analysis by means of a portable mass spectrometer at Sauveterre-de-Béarn, a site along the NPFT where Lefeuvre et al. (2022) measured elevated concentrations of natural H2 in the soil. Furthermore, we also measured the properties of the visited springs (temperature, pH, conductivity) while on site, and performed additional in-situ soil gas measurements from manual drillholes. Details on the measurement and sampling methods, on the laboratory analyses, as well as the results of these measurements and analyses are provided in the data description file The expedition involved six field days in July 2023, during which a total of 26 sites were visited. These sites were selected for their vicinity near a major geological contact or fault zone that could have facilitated upward circulation of gas or (thermal) water from the (deep) subsurface (i.e., potentially from the mantle).

Description: The gravity anomalies reflect density perturbations at different depths, which control the physical state and dynamics of the lithosphere and sub-lithospheric mantle. However, the gravity effect of the crust masks the mantle signals. In this study, we develop two frameworks (correction with density contrasts and actual densities) to calculate the gravity anomalies generated by the layered crust. We apply the proposed approaches to evaluate the global mantle gravity disturbances based on the new crustal models. Consistent patterns and an increasing linear trend of the mantle gravity disturbances with lithospheric thickness and Vs velocities at 150 km depth are obtained. Our results indicate denser lithospheric roots in most cratons and lighter materials in the oceanic mantle. Furthermore, our gravity map corresponds well to regional geological features, providing new insights into mantle structure and dynamics. Specifically, (1) reduced anomalies associated with the Superior and Rae cratons indicate more depleted roots compared with other cratons of North America. (2) Negative anomalies along the Cordillera (western North America) suggest mass deficits owing to the buoyant hot mantle. (3) Positive anomalies in the Baltic, East European, and Siberian cratons support thick, dense lithosphere with significant density heterogeneities, which could result from thermo-chemical modifications of the cratonic roots. (4) Pronounced positive anomalies correspond to stable blocks, e.g., Arabian Platform, Indian Craton, and Tarim basin, indicating a thick, dense lithosphere. (5) Low anomalies in the active tectonic units and back-arc basins suggest local mantle upwellings. (6) The cold subducting/detached plates may result in the high anomalies observed in the Zagros and Tibet.

Description: The 1400 km long North Anatolian Fault Zone in Türkiye runs through numerous densely populated regions, including the city of Düzce that was recently hit by an Mw 6.1 earthquake on 23 November 2022. This was the first moderate event in the region after the devastating Mw 7.2 earthquake in 1999, which cost the lives of over 700 people. Despite its moderate size, the earthquake caused unexpected severe damage to a significant number of buildings, as reported by local institutions (Disaster and Emergency Management Presidency, AFAD). It is well established that ground motions in the near field can lead to increased damage due to near-field domain effects, such as groundmotion pulses and directivity effects (i.e., when the site is aligned with rupture propagation). We examine potential near-field effects using the strong ground motion database of AFAD-Turkish Accelerometric Database and Analysis Systems. To achieve this, we first analyze the behavior of the ground-motion intensities in terms of their spatial distribution and observe higher peak ground velocity than expected by ground-motion models in spatially constrained azimuthal ranges. Furthermore, we find that the majority of the near-fault recordings contain velocity pulses that are primary concentrated on the fault-parallel component. This outcome questions the widely accepted understanding from the previous studies, which mainly suggested that impulsive ground motions that are associated with directivity effects primarily occur on the fault-normal component of large-magnitude events.

Description: This dataset contains 92 estimates from individual studies for groundwater recharge rates on the Arabian Peninsula. Following information is sorted for each study: Location information: Country, Latitude*, Longitude* Estimated groundwater recharge rate: Representative value, Lower/Upper estimate range (all in mm/yr) Estimating methods** Scale of study: Aquifer scale, Study period, Study years Credibility***: Confidence, Confidence criteria (*) Location information was set as the middle point of the study area, in case that spatial coordinates are not given by the authors. (**) If more than 1 methods were used for the estimation, additional methods were written in "Method_2" (***) Confidence of estimates was evaluated by the same criteria used in another meta-study for the African continent (MacDonald et al. 2021; https://doi.org/10.1088/1748-9326/abd661) This dataset has been used to train the neural network model targeting global-scale estimation of groundwater recharge rate together with datasets used in other meta-studies. More detailed information is provided in the paper "Can eXplainable AI offer a new perspective for groundwater recharge estimation? – Global-scale modeling using neural network“.

Description: The fifth meeting of this series took place 5-6 February 2024 at the Helmholtz-Centre for Environmental Research – UFZ. A key topic of this meeting was the formation of Open Source Program Offices. The term is used to describe a concerted effort for an overarching structure in research organizations where research software engineers, computer departments, research data management units, technology/knowledge transfer units, libraries and legal departments cooperatively aim to build an environment conductive to excellent research, excellent research software, open science and technology/knowledge transfer.

Description: Flood-prone people and decision-makers are often unwilling to discuss and prepare for exceptional events, as such events are hard to perceive and out of experience for most people. Once an exceptional flood occurs, affected people and decision-makers are able to learn from this event. However, this learning is often focussed narrowly on the specific disaster experienced, thus missing an opportunity to explore and prepare for even more severe, or different, events. We propose spatial counterfactual floods as a means to motivate society to discuss exceptional events and suitable risk management strategies. We generate a set of extreme floods across Germany by shifting observed rainfall events in space and then propagating these shifted fields through a flood model. We argue that the storm tracks that caused past floods could have developed several tens of km away from the actual tracks. The set of spatial counterfactual floods generated contains events which are more than twice as severe as the most disastrous flood since 1950 in Germany. Moreover, regions that have been spared from havoc in the past should not feel safe, as they could have been badly hit as well. We propose spatial counterfactuals as a suitable approach to overcome society's unwillingness to think about and prepare for exceptional floods expected to occur more frequently in a warmer world.

Description: Excess heat (i.e., Urban Heat Island; UHI) and other urban conditions affect tree physiology with outcomes from enhanced growth to mortality. Resilient urban forests in the face of climate change require species-specific understanding of growth responses. However, previous studies assessing growth dynamics were primarily based on remote sensing of communities rather than individuals, or relied on labor-intensive methods that can limit the spatial coverage necessary to account for highly variable urban growing conditions. Here, we analyze growth dynamics of common urban street tree species over time and across space for Berlin (Germany) combining dendroecological (temporal) and inventory assessments (spatial). First, we show annual increments increased across the 20th century for early (i.e., young) growth. Second, we use an approach relying on open inventory data to identify growth potential in relation to excess heat while accounting for age, potential management effects, and the urban fabric (i.e., planting area; building density, height; available soil nutrients) with generalized additive models for the ten most abundant species. Our analyses showed that younger trees may benefit from increased temperatures, while older individuals feature lower growth at greater UHI magnitudes. Furthermore, planting area as well as building density modulate growth responses to temperature. Lastly, we discuss management implications in the context of climate change mitigation, considering that younger trees are predominantly located at UHI “hot spots” and will undergo the observed age-dependent shift in temperature-growth sensitivity. By relying on increasingly available open data, our approach here is or will be transferable to other urban regions.

Description: We report systematic first-principles results of structural properties and compression behavior based on density functional theory (DFT) and an exchange-correlation functional for solids, of Al-bearing garnets of general compositions in the pyrope-almandine-grossular solid solution system. The combination of DFT and a simple solid solution model is able to produce a compositional dependence of the compression curve consistent with trends observed in experimental studies. Using end-member properties extrapolated from our computations and perturbing an extant thermodynamic model we observe only marginal effects on the bulk sound velocity of pyrolite and MORB along relevant geothermal paths. However, this could hide important effects on the elemental partitioning between garnet and other major phases which should be further investigated both experimentally and computationally. We also present simulations of the effect of combined Fe and Ca substitutions for Mg on the elastic tensor of Al-bearing garnets, our simplified modeling shows only partial agreement with the trends observed in experiments. Therefore, further computational investigations, especially of the effect of Fe-Mg substitution on the tensor, are needed.

Description: Rift-Rift-Rift triple junctions are regions where three plates interact, generating complex networks of variably oriented faults. While the geometry of the fault networks is easily constrained from their surface expression, what remains unclear is how the kinematics of faults and their interactions vary spatially, and how these relate to the unusual crustal motions that result from three plates diverging from each other. The Afar depression lies at the triple junction between the African, Arabian, and Somalian plates (in the Horn of Africa), where the unique combination of observational data from structural mapping, seismicity, and Global Navigation Satellite System (GNSS) allows us to understand the link between fault kinematics and plate motions. We complement these observations with an analog model to gain insights into how the patterns and directions of faults relate to overall plate motions. A key finding in both the model and nature is that some adjacent normal faults form at high angles and generate T-shaped structures. These purely normal faults are synchronously active, which means that the extension direction varies ∼90° locally. These kinematic contrasts in our model and in nature occur despite the relatively smooth pattern of overall surface motions. The results indicate that normal faults interacting at high angles to form the T-shaped structures can evolve synchronously within a stress field that varies gently in magnitude but dramatically in orientation over a few kilometers.

Description: Rift propagation is a 3D thermo-mechanical process that often precedes continental breakup. Pre-existing microcontinental blocks and the associated lithospheric strength heterogeneities influence the style of rift propagation. Interestingly, some rifts propagate into pre-existing blocks and eventually cut through them (e.g., the Zhongsha Block and the Reed Bank), while others bypass these microcontinental blocks forming distinct overlapping rift branches (e.g., the East African Rift System). In this study, we use 3D numerical models to investigate the interaction between microcontinental blocks and rift propagation under different far-field extension rates. In doing so, we assess the impact of mantle lithospheric thicknesses and lower crustal rheology on the style of rift propagation. Our models reproduce the two types of rift propagation, characterized by propagating rifts that either split or bypass the pre-existing microcontinental blocks. We find that lithospheric thickness exerts dominant control, while lower crustal rheology of microcontinental blocks and the extension rate have less effect on rift propagation. Our model results can explain rift propagation patterns, block rotation and strong lithospheric thinning in the South China Sea, the East African Rift System, and the Woodlark Basin.

Description: Opportunistic sensors are increasingly used for rainfall measurement. However, their raw data are collected by a variety of systems that are often not primarily intended for rainfall monitoring, resulting in a plethora of different data formats and a lack of common standards. This hinders the sharing of opportunistic sensing (OS) data, their automated processing, and, at the end, their practical usage and integration into standard observation systems. This paper summarises the experiences of the more than 100 members of the OpenSense Cost Action involved in the OS of rainfall. We review the current practice of collecting and storing precipitation OS data and corresponding metadata, and propose new common guidelines describing the requirements on data and metadata collection, harmonising naming conventions, and defining human-readable and machine readable file formats for data and metadata storage. We focus on three sensors identified by the OpenSense community as prominent representatives of the OS of precipitation: Commercial microwave links (CML): fixed point-to-point radio links mainly used as backhauling connections in telecommunication networks Satellite microwave links (SML): radio links between geostationary Earth orbit (GEO) satellites and ground user terminals. Personal weather stations (PWS): non-professional meteorological sensors owned by citizens. The conventions presented in this paper are primarily designed for storing, handling, and sharing historical time series and do not consider specific requirements for using OS data in real time for operational purposes. The conventions are already now accepted by the ever growing OpenSense community and represent an important step towards automated processing of OS raw data and community development of joint OS software packages.

Description: Digital infrastructures have become indispensable in the field of modern research and science. These technological frameworks play a crucial role for the entire research cycle, supporting literature searches, aiding in data collection and analysis, facilitating the creation and publication of scholarly works, and ensuring the thorough documentation and long-term storage of research findings. Additionally, these infrastructures serve as a vital means for networking and communication among peers, creating the essential foundation of an open and transparent science and research ecosystem. Helmholtz employees were invited to join the Helmholtz Open Science Forum "Towards Open Digital Research Ecosystems - Interconnection Infrastructures" on February 14, 2024, where options for the seamless integration of these digital infrastructures have been discussed. Speakers presented insights into diverse efforts to the provision of open infrastructure structures and how their interconnection offers new possibilities for seamless and integrated workflows within the increasingly digitized research. Further, it was examined how such an integrated ecosystem can support open science practices and vice versa

Description: On January 22, 2024 the Helmholtz Open Science Office hosted the Second Helmholtz Open Science Forum on the topic of Open Science and Transfer. The online event addressed various aspects and issues around the interplay of Open Science, Technology Transfer, Knowledge Transfer and Citizen Science at the Helmholtz Association. Together with the participants important overlaps were identified against the backdrop of the digital transformation. Open science as a standard for scientific work creates foundations for successful transfer - and both topics can complement each other very well. The Helmholtz-internal event gave insights into current projects and initiatives relating to transfer to society, business and industry. Moreover, Helmholtz initiatives for Citizen Science and the successful practical implementation of Open Hardware were presented. The event also offered opportunities for networking and the exchange of ideas. This report documents the Second Helmholtz Open Science Forum on Open Science and Transfer.

Description: Continental crust at temperatures 〉 400 °C and depths 〉 10–20 km normally deforms in a ductile manner, but can become brittle and permeable in response to changes in temperature or stress state induced by fluid injection. In this study, we quantify the theoretical power generation potential of an enhanced geothermal system (EGS) at 15–17 km depth using a numerical model considering the dynamic response of the rock to injection-induced pressurization and cooling. Our simulations suggest that an EGS circulating 80 kg s−1 of water through initially 425 ℃ hot rock can produce thermal energy at a rate of ~ 120 MWth (~ 20 MWe) for up to two decades. As the fluid temperature decreases (less than 400 ℃), the corresponding thermal energy output decreases to around 40 MWth after a century of fluid circulation. However, exploiting these resources requires that temporal embrittlement of nominally ductile rock achieves bulk permeability values of ~ 10–15–10–14 m2 in a volume of rock with dimensions ~ 0.1 km3, as lower permeabilities result in unreasonably high injection pressures and higher permeabilities accelerate thermal drawdown. After cooling of the reservoir, the model assumes that the rock behaves in a brittle manner, which may lead to decreased fluid pressures due to a lowering of thresholds for failure in a critically stressed crust. However, such an evolution may also increase the risk for short-circuiting of fluid pathways, as in regular EGS systems. Although our theoretical investigation sheds light on the roles of geologic and operational parameters, realizing the potential of the ductile crust as an energy source requires cost-effective deep drilling technology as well as further research describing rock behavior at elevated temperatures and pressures.

Description: Using Global Navigation Satellite System-Reflectometry (GNSS-R) for soil moisture (SM) retrieval has recently gained importance due to its high temporal-spatial resolution. However, the current methods, i.e., constructing a single machine learning (ML)-based model, have large model uncertainty resulting from ML networks and input schemes. Moreover, traditional Normalized Difference Vegetation Index (NDVI) cannot capture the rapid vegetation changes well. In this paper, a new SM retrieval method of constructing a hybrid model based on Bayesian model averaging (BMA) is employed to reduce the model uncertainty. Meanwhile, novel Sun-induced fluorescence (SIF) data is used as ancillary data to represent the rapid change of vegetation. We validate the proposed method at point and regional scales using in-situ data and the Global Land Data Assimilation System (GLDAS) product. The results demonstrate that our method has high accuracy and low uncertainty in SM retrieval. At the point scale, as accuracy indices, the average R () of BMA increases from 0.90 to 0.93 and the average root-mean-square-error () decreases from 0.034 to 0.029 ; as indices of uncertainty, the standard deviations of R and RMSE ( and ) decrease by 32 % and 9 % compared to the single ML-based model. For the regional scale, the increases from 0.79 to 0.81, the decreases from 0.024 to 0.023 , and the decreases by 19 %. Moreover, we take the point-scale experiment as an example for comparison to compare the performance of SIF with that of NDVI. The of BMA trained by SIF is 0.03 higher than that trained by NDVI and the decreases by 0.002 ; and decrease by 25 % and 6 %. Based on these results, the proposed method can reduce the uncertainty and the advantage of SIF has potential for improving the SM retrieval.

Description: The Lacq area in southwest France has been associated with continuous moderate induced seismic activity since 1969. However, the mechanisms driving this induced seismicity are not fully understood: reservoir depletion has been proposed as the main factor, and more recently wastewater injection has been suggested to play a more important role (Grasso et al., 2021). The interpretation of these mechanisms relies heavily on the quality of earthquake locations, which we prove to be weak due to a lack of local instrumentation for several years. In order to provide the most complete and reliable induced event catalog for the studies of the Lacq induced seismicity mechanisms & seismic hazard, we made an exhaustive compilation, analysis and improvement of all available catalogs. We also provided new earthquake detections & relocations in a 3D velocity model from past and present temporary deployments never used for studying the Lacq area. Important remaining location uncertainties lead us to also carefully sort the events according to their location confidence, defining 3 classes of events (unconstrained location, location constrained within 2-3 km and 1-2 km respectively). This new harmonized catalog and the identification of well-constrained events, covering 50 years of induced seismicity, allow us to propose that wastewater injection is almost certainly the main mechanism driving the seismicity, with (i) most of the constrained events located within the reservoir boundaries and (ii) the released seismic energy variations following variations in injection operations at different scales. In particular, we have also highlighted a change in the injection-seismicity relationship around 2010–2013. From 2013, despite lower injection volumes, seismicity remained persistent and some clusters of earthquakes were detected predominantly in spring, summer, and early autumn, except in winter periods. From 2016, we observed a strong temporal relationship between days with higher rate/volume injections (approximately above 400m3/day) and both clustered events and higher magnitude earthquakes (greater than 2.4).

Description: This dataset reports measurements from a laboratory incubation of soils sourced from a boreal peatland and surrounding habitats (Siikaneva Bog, Finland). In August 2021, soil cores were collected from three habitat zones: a well-drained upland forest, an intermediate margin ecotone, and a Sphagnum moss bog. The cores from each habitat were taken from surface to approximately 50cm below surface using an Eijelkamp peat corer and subdivided by soil horizon. The samples were then incubated anaerobically for 140 days in three temperature treatment groups (0, 4, 20°C). Subsamples of the incubations headspace (250 µL) were measured on a gas chromatograph (7890A, Agilent Technologies, USA) with flame ionization detection (FID) for CO2 and CH4 concentrations. The rate of respiration from the samples were calculated per gram carbon and per gram soil as described in the method of Robertson., et al. (1999) and reported here, along with other relevant parameters.

Description: The 2022 revision of Aotearoa New Zealand National Seismic Hazard Model (NZ NSHM2022) has involved significant revision of all datasets and model components. In this article, we present a subset of many results from the model as well as an overview of the governance, scientific, and review processes followed by the NZ NSHM team. The calculated hazard from the NZ NSHM 2022 has increased for most of New Zealand when compared with the previous models. The NZ NSHM 2022 models and results are available online.

Description: A seismicity rate model (SRM) has been developed as part of the 2022 Aotearoa New Zealand National Seismic Hazard Model revision. The SRM consists of many component models, each of which falls into one of two classes: (1) inversion fault model (IFM); or (2) distributed seismicity model (DSM). Here we provide an overview of the SRM and a brief description of each of the component models. The upper plate IFM forecasts the occurrence rate for hundreds of thousands of potential ruptures derived from the New Zealand Community Fault Model version 1.0 and utilizing either geologic- or geodeticbased fault-slip rates. These ruptures are typically less than a couple of hundred kilometers long, but can exceed 1500 km and extend along most of the length of the country (albeit with very low probabilities of exceedance [PoE]). We have also applied the IFM method to the two subduction zones of New Zealand and forecast earthquake magnitudes of up to ∼Mw 9.4, again with very low PoE. The DSM combines a hybrid model developed using multiple datasets with a non-Poisson uniform rate zone model for lower seismicity regions of New Zealand. Forecasts for 100 yr are derived that account for overdispersion of the rate variability when compared with Poisson. Finally, the epistemic uncertainty has been modeled via the range of models and parameters implemented in an SRM logic tree. Results are presented, which indicate the sensitivity of hazard results to the logic tree branches and that were used to reduce the overall complexity of the logic tree.

Description: We present a kinematic model developed from geodetic observations, topography analysis and analogue tectonic modelling results, which reveals a striking similarity between the rotational tectonic settings of the Gakkel Ridge-Chersky Range system in the Arctic, and the Central Indian Tectonic Zone within the Indian subcontinent. A crucial aspect of large-scale extensional rift systems is the gradual variation of extension along the rift axis, due to plate rotation about a Euler pole, which may lead to contraction on the opposite side of the Euler pole to form a rotational tectonic system. Our geodetic and topographic analysis, combined with the reanalysis of analogue tectonic modelling results demonstrates such rotational tectonic plate motion in both the Arctic and Indian case. However, the plate boundary between the North American and Eurasian Plates as represented by the Arctic Gakkel Ridge-Chersky Range system is strongly localized, whereas the Central Indian Tectonic Zone that separates the North and South India Plates involves diffuse deformation instead. Furthermore, in both the Arctic and Central Indian we find that the relative Euler rotation pole is located near an indenter-like feature, which possibly controls the present-day rotational tectonics and contrasting topography on opposite sides of the Euler pole.

Description: To test whether a globally inferred sediment thickness value from geomorphological studies can be used as a proxy to predict earthquake site amplification, we derive site-amplification models from the relation between empirical amplification for sites in Europe and Türkiye and the geomorphological sediment thickness. The new site-amplification predictions are then compared to predictions from site-amplification models derived using the traditional site proxies, VS30 inferred from slope, slope itself, and geological era and slope combined. The ability of each proxy to capture the site amplification is evaluated based on the reduction in site-to-site variability caused by each proxy. The results show that the highest reduction is caused by geological era and slope combined, while the geomorphological sediment thickness shows a slightly larger or equal reduction in site-to-site variability as inferred VS30 and slope. We therefore argue that including geology and geomorphology in site-amplification modelling on regional scale can give an important added value and that globally or regionally inferred models for soil and sediment thickness from fields beyond engineering seismology can have a great potential in regional seismic hazard and risk assessments. Furthermore, the differences between the site-amplification maps derived from different proxies capture the epistemic uncertainty of site-amplification modelling. While the different proxies predict similar features on a large scale, local differences can be large. This shows that using only one proxy when predicting site amplification does not capture the full epistemic uncertainty, which is demonstrated by looking into detail on the site-amplification maps predicted for eastern Türkiye and Syria, where the devastating Kahramanmaraş earthquake sequence occurred in February 2023.

Description: The death toll andmonetary damages from landslides continue to rise despite advancements in predictive modeling. These models’ performances are limited as landslide databases used in developing them often miss crucial information, e.g., underlying movement types. This study introduces a method of discerning landslide movements, such as slides, flows, and falls, by analyzing landslides’ 3D shapes. By examining landslide topological properties, we discover distinct patterns in their morphology, indicating different movements including complex ones with multiple coupled movements. We achieve 80- 94% accuracy by applying topological properties in identifying landslide movements across diverse geographical and climatic regions, including Italy, the US Pacific Northwest, Denmark, Turkey, and Wenchuan in China. Furthermore, we demonstrate a real-world application on undocumented datasets from Wenchuan. Our work introduces a paradigm for studying landslide shapes to understand their underlying movements through the lens of landslide topology, which could aid landslide predictive models and risk evaluations.

Description: Bones and teeth are often the only fossil remains of vertebrates that are preserved over geological time in sedimentary rocks. They render valuable archives for geochemical proxies which are commonly used for paleo-reconstructions. However, the fossilization mechanisms of bone are not yet well understood. Crucial processes are the transformation of bioapatite and the replacement of collagen by thermodynamically more stable apatite phases, such as fluorapatite. In the present study, aqueous alteration experiments on cortical bone samples were performed under simulated early diagenetic conditions in order to investigate whether and how an external PO4 source affects post mortem bone mineralization. Additionally, abiotic oxygen isotope exchange mechanisms between bioapatite and aqueous solutions were assessed by using either 18O-enriched water or phosphate as a tracer. The presence of an external sedimentary 18O-labeled PO4 source led to a rapid formation of new fluorapatite crystallites at the sample’s margin that was highly enriched in 18O. Meanwhile, in the interior of the samples carbonate-poor HAp formed through a dissolution-precipitation process without incorporating any of the 18O tracer. These two processes appear to act independently from each other. In samples exposed to 18O-labeled aqueous solutions lacking a PO4 source, no newly grown apatite crystallites were found, however in the interior of these samples, nano-crystalline carbonate-poor or -free hydroxylapatite precipitated. A comparatively low but uniform 18O-enrichment was measured from the sample’s margin towards its interior, which is assumed to have resulted from the adsorption of H218O onto crystallite surface sites and collagen. Overall, our results suggest that a fast incorporation of 18O-doped PO4 from the sediment source accelerated bone mineralization and consequently changed the oxygen isotope composition of the PO4 group in the bone mineral phase more rapidly and to a greater extent than in a diagenetic setting lacking additional external PO4. Dissolved phosphate from the taphonomic setting thus seems to be an important factor fostering bone fossilization and preservation as well as oxygen isotope alteration.

Description: Global climate warming is accelerating permafrost degradation. The large amounts of soil organic matter in permafrost-affected soils are prone to increased microbial decomposition in a warming climate. Along with permafrost degradation, changes to the soil microbiome play a crucial role in enhancing our understanding and in predicting the feedback of permafrost carbon. In this article, we review the current state of knowledge of carbon-cycling microbial ecology in permafrost regions. Microbiomes in degrading permafrost exhibit variations across spatial and temporal scales. Among the short-term, rapid degradation scenarios, thermokarst lakes have distinct biogeochemical conditions promoting emission of greenhouse gases. Additionally, extreme climatic events can trigger drastic changes in microbial consortia and activity. Notably, environmental conditions appear to exert a dominant influence on microbial assembly in permafrost ecosystems. Furthermore, as the global climate is closely connected to various permafrost regions, it will be crucial to extend our understanding beyond local scales, for example by conducting comparative and integrative studies between Arctic permafrost and alpine permafrost on the Qinghai–Tibet Plateau at global and continental scales. These comparative studies will enhance our understanding of microbial functioning in degrading permafrost ecosystems and help inform effective strategies for managing and mitigating the impacts of climate change on permafrost regions.

Description: To investigate the long-term stability of deep rocks, a three-dimensional (3D) time-dependent model that accounts for excavation-induced damage and complex stress state is developed. This model com- prises three main components: a 3D viscoplastic isotropic constitutive relation that considers excavation damage and complex stress state, a quantitative relationship between critical irreversible deformation and complex stress state, and evolution characteristics of strength parameters. The proposed model is implemented in a self-developed numerical code, i.e. CASRock. The reliability of the model is validated through experiments. It is indicated that the time-dependent fracturing potential index (xTFPI) at a given time during the attenuation creep stage shows a negative correlation with the extent of excavation- induced damage. The time-dependent fracturing process of rock demonstrates a distinct interval effect of the intermediate principal stress, thereby highlighting the 3D stress-dependent characteristic of the model. Finally, the influence of excavation-induced damage and intermediate principal stress on the time-dependent fracturing characteristics of the surrounding rocks around the tunnel is discussed. Ó 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

Description: The Lindero deposit is located in the Puna plateau, northwest Argentina, at the southern end of the Central Volcanic Zone of the Central Andes. The high-K calc-alkaline dioritic composition of the subvolcanic intrusions, the shallow emplacement depth (〈 1.5 km), and the gold-rich and copper-depleted mineralization style suggest that the Lindero deposit is a porphyry gold deposit. Porphyry gold deposits are scarce worldwide and the factors controlling their formation are still poorly known. Here we present a detailed study of fluid inclusions in order to characterize the mineralizing fluids that precipitated the Au mineralization at Lindero. Different types of fluid inclusions in quartz veins (A-type and banded quartz), which are associated with the K-silicate alteration, were analyzed using Raman spectroscopy, microthermometry, and LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry). Four inclusion types can be recognized in quartz veins: (i) Salt melt inclusions, which are characterized by a dense packing of daughter minerals (mainly Fe-chloride, sylvite, halite, anhydrite, and hematite), by a distorted vapor bubble, and by the lack of liquid phase; (ii) Halite-bearing inclusions which contain liquid, vapor, and halite; (iii) Two-phase aqueous inclusions that contain liquid and vapor; (iv) Vapor-rich inclusions containing only vapor. The inclusion types are related to different stages of hydrothermal evolution. Stage 1 is the main mineralization stage, characterized by vapor-rich inclusions coexisting with salt melt inclusions. Salt melt inclusions commonly show total homogenization temperature (ThL) 〉 1000 °C. This Na-K-Fe-Cl-rich highly saline brine (~ 90 wt% NaCl eq.) was of magmatic origin and responsible for the Au mineralization. Two later stages involving cooler fluids (ThL 〈 300 °C) and gradually lower salinities (from 36.1 to 0.2 wt% NaCl eq.) trapped by halite-bearing and two-phase aqueous inclusions during stages 2 and 3, respectively, correspond to a late magmatic-hydrothermal system, that is probably related to a deep supercritical fluid exsolution. Salt melt inclusions represent the most likely parental fluid of K-silicate alteration and associated Au mineralization at Lindero. This uncommon type of fluid must have played an important role in Au transport and precipitation in shallow porphyry gold deposits.

Description: Osmium isotope and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundance data are reported for picrites and basalts from the ∼132 Ma Etendeka large igneous province (LIP) and the ∼60 Ma North Atlantic Igneous Province (NAIP). Picrite dykes of the Etendeka LIP have HSE abundances and 187Os/188Os (0.1276 to 0.1323; γOsi = -0.5 to +3.1) consistent with derivation from high-degree partial melting (〉20 %) of a peridotite source with chondritic to modestly supra-chondritic long-term Re/Os. High-3He/4He NAIP picrites from West Greenland represent large-degree partial melts with similarly elevated HSE abundances and 187Os/188Os (0.1273 to 0.1332; γOsi = -0.2 to +3.9). Broadly chondritic Os isotope ratios have also been reported for the ∼132 Ma Paraná LIP and the ∼201 Ma Central Atlantic Magmatic Province (CAMP). Consequently, LIP associated with Atlantic Ocean opening derive, at least in part, from partial melting of peridotite mantle distinct from the depleted mantle associated with mid-ocean ridge basalt volcanism. Modern locations with high-3He/4He (〉25RA) include ocean island basalts (OIB) from Ofu (Samoa), Loihi (Hawaii) and Fernandina (Galapagos) in the Pacific Ocean, and from Iceland, which is considered the modern manifestation of NAIP magmatism. Unlike Etendeka and NAIP picrites, these modern OIB have Sr-Nd-Pb-Os isotopes consistent with contributions of recycled oceanic or continental crust. The lower degree of partial melting responsible for modern high-3He/4He OIB gives higher proportions of fusible recycled crustal components to the magmas, with radiogenic 187Os/188Os and low-3He/4He. The high-3He/4He, incompatible trace element-depleted mantle component in both LIP and OIB therefore also has long-term chondritic Re/Os, which is consistent with an early-formed reservoir that experienced late accretion. Atlantic LIP (CAMP; Paraná-Etendeka; NAIP) provide geochemical evidence for a prominent role for mantle plume contributions during continental break-up and formation of the Atlantic Ocean, a feature hitherto unrecognized in other ocean basin-forming events.

Description: Paleomagnetic records of middle Neoproterozoic (820 to 780 Ma) rocks display high amplitude directional variations that lead to large discrepancies in paleogeographic reconstructions. Hypotheses to explain these data include rapid true polar wander (TPW), a geomagnetic field geometry that deviates from a predominantly axial dipole field, a hyper-reversing field (〉10 reversals/Ma), and/or undiagnosed remagnetization. To test these hypotheses, we collected 1,057 oriented cores over a 85 m stratigraphic succession in the Laoshanya Formation (Yangjiaping, Hunan, China). High precision U-Pb dating of two intercalated tuff layers constrain the age of the sediments between 809 and 804 Ma. Thermal demagnetization isolates three magnetization components residing in hematite which are not time-progressive but conflated throughout the section. All samples possess a north and downward directed component in geographic coordinates at temperatures up to 660°C that is ascribed to a Cretaceous overprint. Two components isolated above 660°C reveal distinct directional clusters: one is interpreted as a depositional remanence, while the other appears to be the result of a mid-Paleozoic (460 to 420 Ma) remagnetization, which is likely widespread throughout South China. The high-temperature directions are subtly dependent on lithology; microscopic and rock magnetic analyses identify multiple generations of hematite that vary in concentration and distinguish the magnetization components. A comparison with other middle Neoproterozoic paleomagnetic studies in the region indicates that the sudden changes in paleomagnetic directions, used elsewhere to support the rapid TPW hypothesis (ca. 805 Ma), are better explained by mixtures of primary and remagnetized components, and/or vertical axis rotations.

Description: Volcanoes produce a variety of seismic signals and, therefore, continuous seismograms provide crucial information for monitoring the state of a volcano. According to their source mechanism and signal properties, seismo‐volcanic signals can be categorized into distinct classes, which works particularly well for short transients. Applying classification approaches to long‐duration continuous signals containing volcanic tremors, characterized by varying signal characteristics, proves challenging due to the complex nature of these signals. That makes it difficult to attribute them to a single volcanic process and questions the feasibility of classification. In the present study, we consider the whole seismic time series as valuable information about the plumbing system (the combination of plumbing structure and activity distribution). The considered data are year‐long seismograms recorded at individual stations near the Klyuchevskoy Volcanic Group (Kamchatka, Russia). With a scattering network and a Uniform Manifold Approximation and Projection (UMAP), we transform the continuous data into a two‐dimensional representation (a seismogram atlas), which helps us to identify sudden and continuous changes in the signal properties. We observe an ever‐changing seismic wavefield that we relate to a continuously evolving plumbing system. Through additional data, we can relate signal variations to various state changes of the volcano including transitions from deep to shallow activity, deep reactivation, weak signals during quiet times, and eruptive activity. The atlases serve as a visual tool for analyzing extensive seismic time series, allowing us to associate specific atlas areas, indicative of similar signal characteristics, with distinct volcanic activities and variations in the volcanic plumbing system.

Description: In this paper, we anticipate geospatial population distributions to quantify the future number of people living in earthquake-prone and tsunami-prone areas of Lima and Callao, Peru. We capitalize upon existing gridded population time series data sets, which are provided on an open-source basis globally, and implement machine learning models tailored for time series analysis, i.e., based on long short-term memory (LSTM) networks, for prediction of future time steps. Specifically, we harvest WorldPop population data and teach LSTM and convolutional LSTM models equipped with both unidirectional and bidirectional learning mechanisms, which are derived from different feature sets, i.e., driving factors. To gain insights regarding the competitive performance of LSTM-based models in this application context, we also implement multilinear regression and random forest models for comparison. The results clearly underline the value of the LSTM-based models for forecasting gridded population data; the most accurate prediction obtained with an LSTM equipped with a bidirectional learning scheme features a root-mean-squared error of 3.63 people per 100 × 100 m grid cell while maintaining an excellent model fit (R2= 0.995). We deploy this model for anticipation of population along a 3-year interval until the year 2035. Especially in areas of high peak ground acceleration of 207–210 cm s−2, the population is anticipated to experience growth of almost 30 % over the forecasted time span, which simultaneously corresponds to 70 % of the predicted additional inhabitants of Lima. The population in the tsunami inundation area is anticipated to grow by 61 % until 2035, which is substantially more than the average growth of 35 % for the city. Uncovering those relations can help urban planners and policymakers to develop effective risk mitigation strategies.

Description: Geomechanics has a marked impact on the safe and sustainable use of the subsurface. This Special Publication contains contributions detailing the latest efforts in present-day in-situ stress characterization, prediction and modelling from the borehole to plate-tectonic scale. A particular emphasis is on the uncertainties that are often associated with geomechanics.

Description: Desert environments constitute one of the largest and yet most fragile ecosystems on Earth. Under the absence of regular precipitation, microorganisms are the main ecological component mediating nutrient fluxes by using soil components, like minerals and salts, and atmospheric gases as a source for energy and water. While most of the previous studies on microbial ecology of desert environments have focused on surface environments, little is known about microbial life in deeper sediment layers. Our study is extending the limited knowledge about microbial communities within the deeper subsurface of the hyperarid core of the Atacama Desert. By employing intracellular DNA extraction and subsequent 16S rRNA sequencing of samples collected from a soil pit in the Yungay region of the Atacama Desert, we unveiled a potentially viable microbial subsurface community residing at depths down to 4.20 m. In the upper 80 cm of the playa sediments, microbial communities were dominated by Firmicutes taxa showing a depth-related decrease in biomass correlating with increasing amounts of soluble salts. High salt concentrations are possibly causing microbial colonization to cease in the lower part of the playa sediments between 80 and 200 cm depth. In the underlying alluvial fan deposits, microbial communities reemerge, possibly due to gypsum providing an alternative water source. The discovery of this deeper subsurface community is reshaping our understanding of desert soils, emphasizing the need to consider subsurface environments in future explorations of arid ecosystems.

Description: The current crustal stress field is of key importance to understand geodynamic processes and to assess stability aspects during subsurface usage. To provide a 3-D continuous description of the stress state, linear elastic forward geomechanical-numerical models are used. These models solve the equilibrium of forces between gravitational volume forces and surfaces forces im- posed mainly by plate tectonics. The latter are responsible for the horizontal stress anisotropy and impose the inverse problem to estimate horizontal displacement boundary conditions that provide a fit best to horizontal stress magnitude data within the model volume. Ho wever , horizontal stress magnitude data have high uncertainties and they are sparse, clustered and not necessaril y representati ve for a larger rock v olume. Even w hen Bay esian statistics are incor - porated and additional stress information such as borehole failure observations or formation integrity test are used to further constrain the solution space, this approach may result in a low accuracy of the model results, that is the result is not correct. Here, we present an alternative approach that removes the dependence of the solution space based on stress magnitude data to avoid potential low accuracy . Initially , a solution space that contains all stress states that are physically reasonable is defined. Stress magnitude data and the additional stress information are then used in a Bayesian framework to e v aluate which solutions are more likely than others. We first show and validate our approach with a generic truth model and then apply it to a case study of the Molasse foreland basin of the Alps in Southern Germany. The results show that the model’s ability to predict a reliable stress state is increasing while the number of likely solutions may also increase, and that outlier of stress magnitude data can be identified. This alternative approach results in a substantial increase in computational speed as we perform most of the calculations anal yticall y.

Description: The ambient-temperature compressibility and room-pressure thermal expansion of two Mg3(PO4)2 polymorphs (farringtonite=Mg3(PO4)2-I, with 5- and 6-fold coordinated Mg, and chopinite=“Mgsarcopside”=[6]Mg3(PO4)2-II), three Mg2PO4OH polymorphs (althausite, hydroxylwagnerite and ɛ- Mg2PO4OH, all with [5]Mg and [6]Mg) and phosphoellenbergerite ([6]Mg) were measured on synthetic powders using a synchrotron-based multi-anvil apparatus to 5.5 GPa and a laboratory high-temperature diffractometer, with whole-pattern fitting procedures. Bulk moduli range from 64.5 GPa for althausite to 88.4 GPa for hydroxylwagnerite, the high-pressure Mg2PO4OH polymorph. Chopinite, based on an olivine structure with ordered octahedral vacancies (K0=81.6 GPa), and phosphoellenbergerite, composed of chains of face-sharing octahedra (K0=86.4 GPa), are distinctly more compressible than their homeotypical silicate (127 and 133 GPa, respectively). The compressibility anisotropy is the highest for chopinite and the lowest for phosphoellenbergerite. First-order parameters of quadratic thermal expansions range from v1=2.19x10-5K-1 for ɛ-Mg2PO4OH to v1=3.58x10-5K-1 for althausite. Phosphates have higher thermal-expansion coefficients than the homeotypical silicates. Thermal anisotropy is the highest for farringtonite and the lowest for hydroxylwagnerite and chopinite. These results set the stage for a thermodynamic handling of phase-equilibrium data obtained up to 3 GPa and 1000°C in the MgO–P2O5–H2O and MgO–Al2O3–P2O5–H2O systems.

Description: Unicellular eukaryotic plankton communities (protists) are the major basis of the marine food web. The spring bloom is especially important, because of its high biomass. However, it is poorly described how the protist community composition in Arctic surface waters develops from winter to spring. We show that mixotrophic and parasitic organisms are prominent in the dark winter period. The transition period toward the spring bloom event was characterized by a high relative abundance of mixotrophic dinoflagellates, while centric diatoms and the haptophyte Phaeocystis pouchetii dominated the successive phototrophic spring bloom event during the study. The data shows a continuous community shift from winter to spring, and not just a dormant spring community waiting for the right environmental conditions. The spring bloom initiation commenced while sea ice was still scattering and absorbing the sunlight, inhibiting its penetration into the water column. The initial increase in fluorescence was detected relatively deep in the water column at ~55 m depth at the halocline, at which the photosynthetic cells accumulated, while a thick layer of snow and sea ice was still obstructing sunlight penetration of the surface water. This suggests that water column stratification and a complex interplay of abiotic factors eventually promote the spring bloom initiation.

Description: The advancement of the Global Geodetic Observing System (GGOS) has enabled monitoring of mass transport and solid-Earth deformation processes with unprecedented accuracy. Coseismic deformation is modelled as an elastic response of the solid Earth to an internal dislocation. Self-gravitating spherical Earth models can be employed in modelling regional to global scale deformations. Recent seismic tomography and high-pressure/high-temperature experiments have revealed finer-scale lateral heterogeneities in the elasticity and density structures within the Earth, which motivates us to quantify the effects of such finer structures on coseismic deformation. To achieve this, fully numerical approaches including the Finite Element Method (FEM) have often been used. In our previous study, we presented a spectral FEM, combined with an iterative perturbation method, to consider lateral heterogeneities in the bulk and shear moduli for surface loading. The distinct feature of this approach is that the deformation of the entire sphere is modelled in the spectral domain with finite elements dependent only on the radial coordinate. By this, self-gravitation can be treated without special treatments employed when using an ordinary FEM. In this study, we extend the formulation so that it can deal with lateral heterogeneities in density in the case of coseismic deformation. We apply this approach to a longer-wavelength vertical deformation due to a large earthquake. The result shows that the deformation for a laterally heterogeneous density distribution is suppressed mainly where the density is larger, which is consistent with the fact that self-gravitation reduces longer-wavelength deformations for 1-D models. The effect on the vertical displacement is relatively small, but the effect on the gravity change could amount to the same order of magnitude of a given heterogeneity if the horizontal scale of the heterogeneity is large enough.

Description: The Bakreswar geothermal province represents a medium enthalpy geothermal system with its Bakreswar and Tantloie hot springs. It lies within the Chotanagpur Granite Gneissic Complex in the eastern part of the Indian Peninsula. The province has a high heat flow and a high geothermal gradient of 90°C/km. Magnetotelluric data from 95 sites in a frequency range of 10 kHz–10 Hz were acquired over the Bakreswar geothermal province to obtain an electrical conductivity model and map the geothermal reservoir with its fluid pathways and related geological structures. Subsurface conductivity models obtained from three-dimensional inversions of the Magnetotelluric data exhibit several prominent anomalies, which are supplemented by gravity results. The conductivity model maps three features which act as a conduit (a) a northwest–southeast trending feature, (b) an east–west trending feature to the south of the northwest–southeast trending feature (which lies 1 km north of the Oil and Natural Gas Corporation fault marked by previous studies) and (c) shallow conducting features close to Bakreswar hot spring. The northwest–southeast trending feature coincides with the boundary of the high-density intrusive block. This northwest–southeast trending feature provides the pathway for the meteoric water to reach a maximum depth of 2.7 km, where it gets heated by interacting with deep-seated structures and then it rises towards the surface. The radiogenic process occurring within the granites of Chotanagpur Granite Gneissic Complex provides the heat responsible for heating the meteoric water. The northwest–southeast and east–west trending features are responsible for the transport of meteoric water to deeper depths and then towards the shallow regions of the Earth. The near surface features close to the Bakreswar hot spring are responsible for carrying the water further towards the hot spring. The resistivity of these structures plotted as a function of salinity and temperatures for saline crustal fluids suggests the involvement of meteoric water. Further, applying Archie's law to this resistivity suggests that the conduit path has a porosity greater than 10%. This study successfully maps the anomalous structures which might foster the migration of geothermal fluid in Bakreswar geothermal province.

Description: Global coupled climate models are in continuous need for evaluation against independent observations to reveal systematic model deficits and uncertainties. Changes in terrestrial water storage (TWS) as measured by satellite gravimetry missions GRACE and GRACE-FO provide valuable information on wetting and drying trends over the continents. Challenges arising from a comparison of observed and modelled water storage trends are related to gravity observations including non-water related variations such as, for example, glacial isostatic adjustment (GIA). Therefore, correcting secular changes in the Earth's gravity field caused by ongoing GIA is important for the monitoring of long-term changes in terrestrial water from GRACE in particular in former ice-covered regions. By utilizing a new ensemble of 56 individual realizations of GIA signals based on perturbations of mantle viscosities and ice history, we find that many of those alternative GIA corrections change the direction of GRACE-derived water storage trends, for example, from gaining mass into drying conditions, in particular in Eastern Canada. The change in the sign of the TWS trends subsequently impacts the conclusions drawn from using GRACE as observational basis for the evaluation of climate models as it influences the dis-/agreement between observed and modelled wetting/drying trends. A modified GIA correction, a combined GRACE/GRACE-FO data record extending over two decades, and a new generation of climate model experiments leads to substantially larger continental areas where wetting/drying trends currently observed by satellite missions coincide with long-term predictions obtained from climate model experiments.

Description: Although many collisional orogens form after subduction of oceanic lithosphere between two continents, some orogens result from strain localization within a continent via inversion of structures inherited from continental rifting. Intracontinental rift-inversion orogens exhibit a range of structural styles, but the underlying causes of such variability have not been extensively explored. We use numerical models of intracontinental rift inversion to investigate the impact of parameters including rift structure, rift duration, post-rift cooling, and convergence velocity on orogen structure. Our models reproduce the natural variability of rift-inversion orogens and can be categorized using three endmember styles: asymmetric underthrusting (AU), distributed thickening (DT), and localized polarity flip (PF). Inversion of narrow rifts tends to produce orogens with more localized deformation (styles AU and PF) than those resulting from wide rifts. However, multiple combinations of the parameters we investigated can produce the same structural style. Thus, our models indicate no unique relationship between orogenic structure and the conditions prior to and during inversion. Because the style of rift-inversion orogenesis is highly contingent upon the rift history prior to inversion, knowing the geologic history that preceded rift inversion is essential for translating orogenic structure into the processes that produced that structure.

Description: The investigation of key minerals including zircon, apatite, titanite, rutile, monazite, xenotime, allanite, baddeleyite and garnet can retain critical information about petrogenetic and geodynamic processes and may be utilized to understand complex geological histories and the dynamic evolution of the continental crust. They act as small but often robust petrochronological capsules and provide information about crustal evolution, from local processes to plate tectonics and supercontinent cycles. They offer us insights into processes of magmatism, sedimentation, metamorphism and alteration, even when the original protolith is not preserved. In situ techniques have enabled a more in-depth understanding of trace element behaviour in these minerals within their textural context. This has led to more meaningful ages for many stages of geological events. New developments of analytical procedures have further allowed us to expand our petrochronological toolbox while improving precision and accuracy. Combining multiple proxies with multiple minerals has contributed to new interpretations of the crustal history of our planet.

Description: Silicon isotope fractionation during silicification is poorly understood and impedes our ability to decipher paleoenvironmental conditions from Si isotopes in ancient cherts. To investigate isotope fractionation during silica-for‑carbonate replacement we analyzed the microscale Si and O isotope composition in different silica phases in a silicified zebra dolostone as well as their bulk δ18O and Δ’17O compositions. The subsequent replacement of carbonate layers is mimicked by decreasing δ18O and δ30Si. The textural relationship and magnitude of Si and O isotope fractionation is best explained by near-quantitative silica precipitation in an open system with finite Si. A Rayleigh model for silicification suggests positive Ɛ30/28Si during silicification, conforming with predictions for isotope distribution at chemical equilibrium from ab-initio models. Application of the modelled Ɛ30Si-T relationship yields silicification temperatures of approx. 50 °C. To reconcile the δ18Ochert composition with these temperatures, the δ18O of the fluid must have been between −2.5 and − 4 ‰, compositions for which the quartz phases fall close to the oxygen equilibrium fractionation line in three-isotope space. Diagenetic silica replacement appears to occur in O and Si isotopic equilibrium allowing reconstructions of temperatures of silicification from Si isotopes and derive the δ18O composition of the fluid – a highly desired value needed for accurate reconstructions of the temperature- and δ18O histories of the oceans.

Description: In this work, IMF By effects on field-aligned currents (FACs) are examined in different local time sectors, seasons, and hemispheres. At dusk and 09–14 MLT, when the eastward polar electrojet (PEJ) prevails, the northern FACp (poleward side FACs) are stronger when IMF By 〈 0 than when IMF By 〉 0. Conversely, at dawn, 21–02 MLT, and 09–14 MLT with westward PEJ, the northern FACp are stronger with IMF By 〉 0 compared to IMF By 〈 0. The southern FACp shows a reversed relationship with IMF By direction. The dependence of FACe (equatorward side FACs) on IMF By is weaker, except for the midday FACe, which shows opposite variations with respect to IMF By when compared to FACp. Stronger IMF By effect is observed in local summer in most of local times. The northern FACs are located at higher latitude for IMF By 〉 0 than for IMF By 〈 0 in local times with eastward PEJ, while the opposite trend is observed in other local times and in the Southern Hemisphere. The hemispheric difference in the peak latitude of FACs demonstrates an inverse relationship with its intensity, with stronger FACs located at lower latitudes. Overall, the local time and hemispheric differences in FACs strength and latitude are discussed in the context of interhemispheric field-aligned currents linked to IMF By.

Description: The Zagros Fold and Thrust Belt (ZFTB) is an outstanding orogen running from eastern Turkey to the Makran area. It is formed as a consequence of the convergence between the Arabian and the Eurasian plates that occurred in the Neogene. This still active and long-lasting process generated a topographic configuration dominated by a series of parallel folding structures which, at places, isolate internal basins. The topographic configuration has, in turn, profoundly influenced the river network evolution, which follows a trellis pattern with the main valleys developed in the synclines and rivers that occasionally cut into anticlines. The peculiar climate, characterised by arid and semi-arid conditions, makes most of the rivers ephemeral, alimented only by short rainfall events. For this reason, the sediments are transported over short distances and deposited in huge alluvial fans. Although the Zagros is one of the most studied belts in the world, its tectonic evolution is far from being fully understood. Debated, for example, are the beginning of collision, the primary deformation mechanism, the evolution of the drainage system, the formation process of the alluvial fans, and the interrelations between landscape, tectonics, and climate. This paper, focusing on the geodynamic, geological, stratigraphic, and topographic configuration of the Zagros belt, is intended to be a compendium of the most up-to-date knowledge on the Zagros and aims to provide the cognitive basis for future research that can find answers to outstanding questions.

Description: Slow slip events (SSEs) have been observed in spatial and temporal proximity to megathrust earthquakes in various subduction zones, including the 2014 Mw 7.3 Guerrero, Mexico earthquake which was preceded by a Mw 7.6 SSE. However, the underlying physics connecting SSEs to earthquakes remains elusive. Here, we link 3D slow‐slip cycle models with dynamic rupture simulations across the geometrically complex flat‐slab Cocos plate boundary. Our physics‐based models reproduce key regional geodetic and teleseismic fault slip observations on timescales from decades to seconds. We find that accelerating SSE fronts transiently increase shear stress at the down‐dip end of the seismogenic zone, modulated by the complex geometry beneath the Guerrero segment. The shear stresses cast by the migrating fronts of the 2014 Mw 7.6 SSE are significantly larger than those during the three previous episodic SSEs that occurred along the same portion of the megathrust. We show that the SSE transient stresses are large enough to nucleate earthquake dynamic rupture and affect rupture dynamics. However, additional frictional asperities in the seismogenic part of the megathrust are required to explain the observed complexities in the coseismic energy release and static surface displacements of the Guerrero earthquake. We conclude that it is crucial to jointly analyze the long‐ and shortterm interactions and complexities of SSEs and megathrust earthquakes across several (a)seismic cycles accounting for megathrust geometry. Our study has important implications for identifying earthquake precursors and understanding the link between transient and sudden megathrust faulting processes.

Description: Fault‐damage zones comprise multiscale fracture networks that may slip dynamically and interact with the main fault during earthquake rupture. Using 3D dynamic rupture simulations and scale‐dependent fracture energy, we examine dynamic interactions of more than 800 intersecting multiscale fractures surrounding a listric fault, emulating a major listric fault and its damage zone. We investigate 10 distinct orientations of maximum horizontal stress, probing the conditions necessary for sustained slip within the fracture network or activating the main fault. Additionally, we assess the feasibility of nucleating dynamic rupture earthquake cascades from a distant fracture and investigate the sensitivity of fracture network cascading rupture to the effective normal stress level. We model either pure cascades or main fault rupture with limited offfault slip. We find that cascading ruptures within the fracture network are dynamically feasible under certain conditions, including: (a) the fracture energy scales with fracture and fault size, (b) favorable relative pre‐stress of fractures within the ambient stress field, and (c) close proximity of fractures. We find that cascading rupture within the fracture network discourages rupture on the main fault. Our simulations suggest that fractures with favorable relative pre‐stress, embedded within a fault damage zone, may lead to cascading earthquake rupture that shadows main fault slip. We find that such off‐fault events may reach moment magnitudes up to Mw ≈ 5.5, comparable to magnitudes that can be otherwise hosted by the main fault. Our findings offer insights into physical processes governing cascading earthquake dynamic rupture within multiscale fracture networks.

Description: Wetlands in Arctic drained lake basins (DLBs) have a high potential for carbon storage in vegetation and peat as well as for elevated greenhouse gas emissions. However, the evolution of vegetation and organic matter is rarely studied in DLBs, making these abundant wetlands especially uncertain elements of the permafrost carbon budget. We surveyed multiple DLB generations in northern Alaska with the goal to assess vegetation, microtopography, and organic matter in surface sediment and pond water in DLBs and to provide the first high-resolution land cover classification for a DLB system focussing on moisture-related vegetation classes for the Teshekpuk Lake region. We associated sediment properties and methane concentrations along a post-drainage succession gradient with remote sensing-derived land cover classes. Our study distinguished five eco-hydrological classes using statistical clustering of vegetation data, which corresponded to the land cover classes. We identified surface wetness and time since drainage as predictors of vegetation composition. Microtopographic complexity increased after drainage. Organic carbon and nitrogen contents in sediment, and dissolved organic carbon (DOC) and dissolved nitrogen (DN) in ponds were high throughout, indicating high organic matter availability and decomposition. We confirmed wetness as a predictor of sediment methane concentrations. Our findings suggest moderate to high methane concentrations independent of drainage age, with particularly high concentrations beneath submerged patches (up to 200 μmol l−1) and in pond water (up to 22 μmol l−1). In our DLB system, wet and shallow submerged patches with high methane concentrations occupied 54% of the area, and ponds with high DOC, DN and methane occupied another 11%. In conclusion, we demonstrate that DLB wetlands are highly productive regarding organic matter decomposition and methane production. Machine learning-aided land cover classification using high-resolution multispectral satellite imagery provides a useful tool for future upscaling of sediment properties and methane emission potentials from Arctic DLBs.

Description: We present a seismic catalog (Bindi et al., 2024, https://doi.org/10.5880/GFZ.2.6.2023.010) including energy magnitude Me estimated from P waves recorded at teleseismic distances in the range 20° 1 98° and for depths shorter than 80 km. The catalog is built starting from the event catalog disseminated by GEOFON (GEOFOrschungsNetz), considering 6349 earthquakes with moment magnitude Mw 5 occurring between 2011 and 2023. Magnitudes are computed using 1 031 396 freely available waveforms archived in EIDA (European Integrated Data Archive) and IRIS (Incorporated Research Institutions for Seismology) repositories, retrieved through the standard International Federation of Digital Seismograph Networks (FDSN) web services (https://www.fdsn.org/webservices/, last access: March 2024). A reduced, high-quality catalog for events with Mw 5〉_8 and from which stations and events with only few recordings were removed forms the basis of a detailed analysis of the residuals of individual station measurements, which are decomposed into station- and event-specific terms and a term accounting for remaining variability. The derived Me values are compared to Mw computed by GEOFON and with the Me values calculated by IRIS. Software and tools developed for downloading and processing waveforms for bulk analysis and an add-on for SeisComP for real-time assessment of Me in a monitoring context are also provided alongside the catalog. The SeisComP add-on has been part of the GEOFON routine processing since December 2021 to compute and disseminate Me for major events via the existing services.

Description: The West Siberian Seaway connected the Tethys to the Arctic Ocean in the Paleogene and played an important role for Eurasian-Arctic biogeography, ocean circulation, and climate. However, the paleogeography and geological mechanisms enabling the seaway are not well constrained, which complicates linking the seaway evolution to paleoenvironmental changes. Here, we investigate the paleogeography of the Peri-Tethys realms for the Cenozoic time (66–0 Ma), including the West Siberian Seaway, and quantify the influence of mantle convection and corresponding dynamic topography. We start by generating continuous digital elevation models for Eurasia, Arabia, and Northern Africa, by digitizing regional paleogeographic maps and additional geological information and incorporate them in a global paleogeography model with nominal million-year resolution. Then we compute time-dependent dynamic topography for the same time interval and find a clear correlation between changes in dynamic topography and the paleogeographic evolution of Central Eurasia and the West Siberian Seaway. Our results suggest that mantle convection played a greater role in Eurasian paleogeography than previously recognized. Mantle flow may have influenced oceanic connections between the Arctic and global ocean providing a link between deep mantle convection, surface evolution, and environmental changes. Our reconstructions also indicate that the Arctic Ocean may have been isolated from the global ocean in the Eocene, even if the West Siberian Seaway was open, as the Peri-Tethys – Tethys connection was limited, and the Greenland-Scotland Ridge was a landbridge.

Description: To reach their net-zero targets, countries will have to compensate hard-to-abate CO2 emissions through carbon dioxide removal (CDR). Yet, current assessments rarely include socio-cultural or institutional aspects or fail to contextualize CDR options for implementation. Here we present a context-specific feasibility assessment of CDR options for the example of Germany. We assess 14 CDR options, including three chemical carbon capture options, six options for bioenergy combined with carbon capture and storage (BECCS), and five options that aim to increase ecosystem carbon uptake. The assessment addresses technological, economic, environmental, institutional, social-cultural and systemic considerations using a traffic-light system to evaluate implementation opportunities and hurdles. We find that in Germany CDR options like cover crops or seagrass restoration currently face comparably low implementation hurdles in terms of technological, economic, or environmental feasibility and low institutional or social opposition but show comparably small CO2 removal potentials. In contrast, some BECCS options that show high CDR potentials face significant techno-economic, societal and institutional hurdles when it comes to the geological storage of CO2. While a combination of CDR options is likely required to meet the net-zero target in Germany, the current climate protection law includes a limited set of options. Our analysis aims to provide comprehensive information on CDR hurdles and possibilities for Germany for use in further research on CDR options, climate, and energy scenario development, as well as an effective decision support basis for various actors.

Description: In this study, we investigated four different ferroan dolomite samples using in situ Raman spectroscopy and powder X-ray diffraction (XRD) at high pressures up to 48 GPa and at room temperature. Our results show that the transition from Dolomite-I (Dol-I) to Dolomite-II (Dol-II) occurs above 13-16 GPa, and the transition pressure depends on the composition of the solid solution. Compression above 32-35 GPa results in the appearance of the Dolomite-IIIc (Dol-IIIc) or Dolomite-IIIb (Dol-IIIb). In the high-pressure XRD study, we found that the XRD patterns of the Ca0.97(Mg0.77,Fe0.23Mn0.03)(CO3)2 (xFe = 0.23, Ank23) can be indexed as Dol-IIIc at 44 GPa, while the rhombohedral Dol-IIIb structure matches better with the XRD patterns of the xFe = 0.40 (Ank40) and 0.64 (Ank64) solid solutions. Additionally, in the Raman spectra of the Fe-richest sample (Ca0.99(Mg0.33Fe0.64Mn0.05) (CO3)2 (Ank64), we observed an abrupt frequency downshift of the CO3-stretching vibrations between 40 – 42 GPa, which may reflect a pressure-induced Fe2+ spin transition. We further investigated two samples with xFe= 0.19 (Ank19) and 0.23 (Ank23) at high pressure and high temperatures, up to at least 2600 K. The experiments revealed that the unquenchable Dol-IIIc structure could be a stable high-pressure/high-temperature polymorph in ferroan dolomite up to at least 2600 K.

Description: Due to the difficulties in estimating groundwater recharge and cross-boundary nature of many aquifers, estimating groundwater recharge at large scale has been called upon. Process-based models as well as data-driven models have been established to meet this need. Meanwhile, with the advent of explainable artificial intelligence (XAI) methods, data-driven machine learning models can take advantage of enhanced explainability while keeping the strength of high flexibility. In this study, an ensemble neural network model was built to check the suitability of the model to predict groundwater recharge and the possibility to gain new insights from large data set. Recent large inputs of groundwater recharge data and additional input for the Arabian Peninsula collated in this study were fed to the model with multiple predictors related to climatology considering seasonality, soil and plant characteristics, topography, and hydrogeology. The model showed higher performance (adjusted R2: 0.702, RMSE: 193.35 mm yr−1) than a recent global process-based model in predicting groundwater recharge. Using XAI methods as individual conditional expectations and Shapley Additive Explanation interaction values, the model behavior was analyzed and possible linear and non-linear relationships between the predictors and the groundwater recharge rate were found. Long-term averaged precipitation and enhanced vegetation index showed non-linear relationships with groundwater recharge rate, while slope, compound topographic index, and water table depth showed low importance to the model results. Most model behaviors followed the domain knowledge, while multi-correlation between predictors and data skewness hindered the model from learning.