Pre-print: Ground Motion Shaking Predictions Based on Machine Learning and Physics-based SimulationsEarthquakes constitute a major threat to human lives and infrastructure, hence it is crucial to quickly assess the intensity of ground motions after a major seismic event. Rapid estimation of the intensity of ground vibrations is essential to assess the impact after a major earthquake occurs. The Machine Learning Estimator for Ground Shaking Maps (MLESmap) introduces an innovative approach that harnesses the predictive capabilities of Machine Learning (ML) algorithms, utilizing high-quality physics-based seismic scenarios. MLESmap aims to provide ground intensity measures within seconds following an earthquake. The inferred information can produce shaking maps of the ground providing quasi-real-time affectation information to help us explore uncertainties quickly and reliably. To develop the MLESmap technology, we used ground-motion simulations generated by the CyberShake platform. Originally designed for Southern California, this physics-based Probabilistic Seismic Hazard Methodology was migrated to the South Iceland Seismic Zone recently. Our methodology follows a three-step process: simulation, training, and deployment. By employing this approach, we can generate the next generation of ground shake maps, incorporating essential physical information derived from wave propagation, such as directivity, topography, and site effects. Remarkably, the evaluation times for MLESmap are comparable to empirical Ground Motion Models, whereas the predictive capacity of the former is superior for the Mw > 5 earthquakes.In this work, we present the application of the MLESmap methodology in South West Iceland.

How fast a plume can stitch two cratonic nuclei into a stable one remains under-investigated. The Tarim continental block in central Asia is recratonized by a Permian-aged plume and preserves a complete record before, during, and after the plume-driven recratonization. Here we conduct area-depth analysis on seismic reflection data from the central Tarim Basin to date the Phanerozoic deformation. All thrusts and strike-slip faults investigated underwent an early deformation stage (Earliest Ordovician-Middle Devonian), a hiatus stage (Late Devonian-Late Permian), and a newly-discovered deformation stage throughout the Mesozoic. Both deformation stages within Tarim are driven by the subduction and accretion surrounding the block. The Mesozoic finite strains highlight the continuous adjustment as the plume-welded continental lithosphere heals and strengthens. The Tarim plume-driven recratonization concludes not immediately, but ~200 Myr after the plume activity ceased, establishing a characteristic timescale for such events in Earth’s history.

Mass balance is of great significance in earth sciences. Isocon method is simple and efficient in mass-transfer calculation. However, problems exist in the identification of immobile components, the choice of the parental sources' compositions, and visualisation. This paper demonstrated that mobility is a relative concept, and the distribution coefficient is the characteristic quantity to describe component mobility. Absolute immobile components are those components with distribution coefficients approaching infinity. The general straight line connecting the origin to the data point of any component carries information on the mass mobility of the component and the evolution degree of the system. Isocon line is a special case of such straight lines. The relationship between final evolved concentrations and the original concentrations is expressed by an equation deduced from mass conservation law and component conservation law, which says the final evolved concentration is determined by the original concentration, distribution coefficient, and the evolution degree. This equation is suitable for all the evolution processes, as long as its mass conserved. Three special Isocon lines were defined, initial Isocon line is the reference line for all the other Isocon lines, absolute Isocon line reflects the evolutionary degree and is formed by absolute immobile components, and relative Isocon line is formed by components having the same/similar distribution coefficients. The components lying on one relative Isocon line are relative immobile to each other, and their ratio equals the original ratio in the initial system. The principle on selection of approximation of absolute immobile components was proposed based on the relationship between the slope and distribution coefficient. A rough knowledge framework on mobility and Isocon analysis was revised and reorganized.

Fractures play important roles in fluid and heat flow during heat extraction from an enhanced geothermal system (EGS). Quantifying the associated uncertainties in fractures is critical for predicting long-term thermal performance of EGSs. Considerable advancements have been made regarding the inversion of fracture characteristics such as aperture distribution. However, most previous studies assumed a constant fracture aperture to simplify the inversion, while both experimental and numerical results indicated significant variations in fracture aperture due to complex thermo-hydro-mechanical (THM) coupled processes during heat extraction. This study introduces a multi-stage inversion framework that integrates the Ensemble Smoother with Multiple Data Assimilation (ES-MDA) with a THM coupled model to capture the dynamic evolution of fracture aperture. The framework executes multiple aperture inversions at different times during EGS operation. In each inversion stage, we use ES-MDA to invert for fracture aperture by assimilating tracer data, and then perform THM modeling to analyze fracture aperture evolution under coupled THM processes and predict thermal performance. We propose a principle to assure a smooth transition between two consecutive inversion stages, that the posterior aperture fields obtained in an inversion stage are used as the prior aperture fields for the following stage, and the temperature field simulated in the previous inversion stage serves as the initial temperature field for the following stage. Application of the framework to a synthetic field-scale EGS model demonstrates its efficacy in capturing the dynamic evolution of fracture aperture, resulting in more accurate thermal predictions compared with previous inversion methods assuming constant fracture aperture.

A document by Sebastian H.G. Walter. Click on the document to view its contents.

A document by Andy Baker. Click on the document to view its contents.

NIST is an important leader in the US for setting standards that inform best practices for scientific research and innovation. AGU's response to the RFI is based on our experience working with Earth, space, and environmental science researchers as well as computer and information scientists and data and software experts in the work that we are doing in promoting FAIR and open software sharing in AGU journals and in the wider community. 

A document by Kristina Vrouwenvelder. Click on the document to view its contents.

Carbonate rocks frequently undergo remagnetisation events, which can partially/completely erase their primary detrital remanence and introduce a secondary component through thermoviscous and/or chemical processes. Despite belonging to different basins hundreds of kilometres apart, the Neoproterozoic carbonate rocks of South America (over the Amazon and São Francisco cratons) exhibit a statistically indistinguishable single-polarity characteristic direction carried by monoclinic pyrrhotite and magnetite, with paleomagnetic poles far from an expected detrital remanence. We use a combination of classical rock magnetic properties and micro-to-nanoscale imaging/chemical analysis using synchrotron radiation to examine thin sections of these remagnetised carbonate rocks. Magnetic data shows that most of our samples failed to present anomalous hysteresis properties, usually referred to as part of the “fingerprints” of carbonate remagnetisation. Combining scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), highly sensitive X-ray fluorescence (XRF), and X-ray absorption spectroscopy (XAS) revealed the presence of subhedral/anhedral magnetite, or spherical grains with a core-shell structure of magnetite surrounded by maghemite. These grains are within the pseudo-single domain size range (as well as most of the iron sulphides) and spatially associated with potassium-bearing aluminium silicates. Although fluid percolation and organic matter maturation might play an important role, smectite-illitisation seems a crucial factor controlling the growth of these phases. X-ray diffraction analysis identifies these silicates as predominantly highly crystalline illite, suggesting exposure to epizone temperatures. Therefore, we suggest that the remanence of these rocks should have been thermally reset during the final Gondwana assembly, and locked in a successive cooling event during the Early-Middle Ordovician.

The threshold of motion of bioclastic sediments is the fundamental aspect for understanding of sediment dynamics in coral reef systems while there are currently few studies on its prediction. We conducted laboratory experiments, and showed that the threshold of motion of coral skeletal grains is more appropriately characterized by the nominal diameter and particle density that is defined as the density of grains with its skeletal void filled by the fluid. Distinctions in threshold of motion of observed coral particles and other bioclastic sediments arise from the influences of grain density and shape, resulting in a notable departure from existing empirical thresholds based on quartz sand. We then propose a new formula for estimating critical shear velocity of bioclastic sediments by introducing a grain shape parameter. The new comprehensive criterion improves the understanding of threshold of motion of bioclastic sediments with highly heterogeneous properties under steady unidirectional flow.

A document by Fanyu Zhang. Click on the document to view its contents.

Many convergent tectonic belts show large-scale transverse folding affecting the earlier fold structures and their associated rock fabrics. The origin of such cross folds is generally explained in terms of a different deformation episode, separated in time from the main orogenic events, considering a reorientation of the tectonic stress axes. This study reports cross folds from the North Singhbhum Mobile belt (NSMB), claiming their development in the course of a single unidirectional convergent movement. A southward convergence in the NSMB resulted in localized thrusting of the NSMB over the Singhbhum craton (SC), coupled with regional (distributed) ductile deformations producing orogen parallel folds (F1) and fabrics (S1) on a wide range of scales. The structural mapping reveals overprinting of NE-SW trending cross folds (F2) in the eastern flank of NSMB, giving rise to a series of crustal scale culminations and depressions. Scaled laboratory experiments were conducted on a scaled representative NSMB model by temporally varying the tectonic convergence rate (Vc). The experimental runs had an initial period of fast-rate convergence (Stage I: Vc = 16 mm/yr), followed by an intermediate (Stage II: Vc = 8 mm/yr) and an extremely slow (Stage III: Vc = 0.8 mm/yr) rate. During Stages I and II, the arcuate SC geometry causes the NSMB to undergo heterogeneous shortening, forming elevated surface topography preferentially in the northern part of the SC. The maximum horizontal instantaneous stretching axes (ISAHmax) are oriented grossly E-W in these two stages. The differential horizontal crustal flows develop a distinct region of dextral shear in the eastern flank of NSMB that causes the finite strain axes (i.e., F1 folds and S1 schistosity) to reorient along NW-SE orientations in this part. With slowing down of the Vc in Stage III, the elevated topography in the northern part undergoes gravitational collapse, setting in a dominant SE-directed crustal flow around the SC. This flow generates NW-SE compression in the eastern flank of NSMB, which in turn produces cross folds on small to large scales. A time-series strain analysis from the model suggests tectonic deformations varying from flattening to plane strain and constriction type in space and time across NSMB.  

Previous workers have used stratigraphic studies to identify three potential marine gateways that connected the Atlantic and Mediterranean during the Messinian salinity crisis (MSC): the Strait of Gibraltar that remains a 300-900-m-deep channel to the present-day and the Betic and Rifian corridors now exposed on-land in southern Spain and northern Morocco, respectively. Comparison of deepsea cores from the Atlantic and Mediterranean have shown that there was no significant or sea-level rise during the Messinian leaving a tectonic or climate control as the most likely cause for Messinian drying of the Mediterranean and that was followed in the early Pliocene by the re-flooding of Atlantic waters in the dessicated and evaporite-filled Mediterranean basin. In this study, we integrate bathymetric, GPS data from the Tangier Peninsula and its offshore areas with paleostress measurements at 25 sites ranging in age from Jurassic to Miocene. Offshore data from the Strait of Gibraltar indicates that the main ENE-lineament on the seafloor is a major right-lateral strike-slip fault whose sense is consistent with: 1) WNW-trending GPS vectors; 2) the arrangement of positive restraining and negative releasing bends; 3) formation of a 15-20-km-wide syncline within the Strait that deepened with continued compression; and 5) the right-lateral offset of the Mesozoic Calcaire Dorsale Ridge by ~7 km. Paleostress sites on-land in rocks of Oligocene to early Pliocene age indicate three events: 1) east-west compression of Miocene age inferred to record the formation and eastward motion of the Gibraltar arc; 2) NW-SE compression inferred to record the closure of Nubia and Iberia with compression of the Gibraltar arc; and 3) NE-SW compression inferred to represent continued compression of the Gibraltar arc that accompanied continued formation of the large syncline within the strait. We postulate that the offset of the highly resistant and 1-km-thick Calcaire Dorsale allowed the initial deep channels to open between the Atlantic and Mediterranean. We see no evidence for north-south-striking normal faults as postulated in strait-opening models based on roll-back of the Gibraltar slab.

A document by Drew Cochran. Click on the document to view its contents.

The Gulf of Mexico (GoM) is a passive rift margin that is shrouded in thick sedimentary layers, making it challenging to trace its Mesozoic evolution. Traditionally, plate tectonic models have required an assumption of rigid plates, limiting our ability to understand the evolution of passive margins given the wealth of geological and geophysical evidence indicating significant crustal deformation during rifting processes. However, recent advances have been made in our ability to incorporate deformation into plate tectonic models.Here, we present a novel approach to reconstruct the evolution of the GoM by using an optimized and focused deformable plate model. Our new model uses a time-evolving focused deformation along the rift, where the strain rate evolves over time from being more uniform initially to increasing exponentially seaward to the point of continental rupture and ocean crust formation.By incorporating time-evolving deformation into our plate reconstruction, we can additionally derive crustal thickness and thermal and tectonic subsidence through time, which allows us to better explore the depositional history of the presalt deposition and crustal architecture evolution of the GoM basin. Our deformation model is optimized to minimize the root mean squared error (RMSE) between predicted present-day crustal thickness and the GEMMA crustal thickness model, resulting in an RMSE of 5.6 km compared to GEMMA, with <2 km absolute error in the northwest and northeast GoM. The resulting tectonic subsidence of ~1.5 km before the Yucatán block drifted in Late Triassic providing routes for the deposition of red beds through the paleo-drainage systems of the northern GoM as successor basin infilling. We find rapid subsidence occurred in the central GoM during the Early Jurassic shifting red bed deposition to a location that presently lies beneath the salt formation, potentially reconciling ~40 Myrs of missing sedimentary strata. Extension rate and stretching factor calculations reveal a transition from a magma-rich to a hyperextended margin, with possible mantle exhumation.Through our study, we highlight the significance of adopting optimized deformable plate reconstruction models, which enables quantitative interpretations of the tectonic history and geological evolution in rift basins globally.

“Pressure and time.” A momentous quote in a compelling movie from a few decades ago interestingly pointed at some of the ingredients that contributed to shaping the Earth. The movie set off from how to seep through masses that appeared just too vast to be shakable or vulnerable – if not by deciphering their inner core. The planetary size and time frame of the Earth may have elicited a perception of a durable, unbuckling living environment – just because “pressure and time” to really affect it would have been out of human reach – supposedly. However, the Earth and environmental sciences have long striven to alert contemporary societies that this is just not the case, as humans have been well exerting scattered yet ubiquitous, planetary-scale pressure over a relatively brief time – with consequential, durable effects. Rising global population, long-term migration shifts of continental extents – due to risks, climate, resources – and unpredicted factors – from vulnerabilities to instabilities – pressure on the environment (natural and built) in unprecedented scale throughout human history. The Earth sciences were born out of deciphering ancient life forms teeming in an aboriginal environment, unfolding on a planet that could be explained only by looking at the Solar system – and at the inception of the Universe.Cross-disciplinary by nature, the Earth and environmental sciences offer crucial tools to gauge location, economic turnout, and societal costs of those very resources and fragilities. They also are pivotal co-actors of intellectual stewardship bridging the gulf with sister disciplines well beyond the remits of the physical sciences. From economics to philosophy, and from history to literature, multiple, diverse and concurring threats call for resourceful, multi-faceted mind- and skill-sets where no single hazard may be really treated apart – not on societal terms.Adapting a famous statement from the 20th century, evolution in a time of poly-crises, multiple hazards, and accrued vulnerabilities is not going to be a dinner party for contemporary societies – especially as they dwell a world perceived as increasingly richer in risks and poorer in resources, with a growing population and across instabilities. Human Earth sciences offer a bridge towards our collective future – as societies, continents, planets.Earth-prints @ INGV  

The Pra Basin in Ghana is well-known for its abundant mineral resources, dense forest coverage, and fertile soil. The region faces major water management challenges due to illegal mining practices, resulting in surface water pollution and necessitating groundwater use as an alternate water source. Unfortunately, there is limited information available regarding the chemical characteristics of groundwater in the region, posing challenges for water management. This study examined the quality, hydrochemical variability and geochemical processes driving the chemical evolution of the groundwater. Samples of surface water and groundwater were collected and analyzed for chemical parameters. We employed multivariate statistics, including cluster and factor analysis, to identify regional variations and interrelationships among the parameters. The resulting clusters were used to formulate a hypothetical groundwater flow path to model the geochemical reactions that control the groundwater composition using combinatorial inverse modelling based on the local thermodynamic equilibrium hypothesis. The weathering of silicate minerals, including albite, anorthite, chalcedony, and k-feldspar, was found to be the dominant process driving the groundwater's chemical evolution. Models adequately predicted the composition of groundwater along the flow path and serve as a guide for the development of sustainable water resource management strategies for the catchment. Overall, our modelling approach presented here can be useful in regions with large variability in water chemistry and limited knowledge of aquifer mineralogy.

Here we present a dissemination method that combines science and art to visualize a seismic experiment conducted in northern Chile. Through the expertise of an illustrator using digital watercolor techniques and a science journalist who contributed her expertise in creating plain-language keynotes, we created six visually compelling art pieces to summarize the progress and results of the first year of a project funded by Fondecyt-ANID. The artwork, called “Images of Silence” (Imágenes del Silencio, originally in spanish), plays with the concepts of silence and images. Here, the quitness of the desert is often interrupted by the loudness of seismic activity. Additionally, the illustrations - images to tell a story - offers a narrative for a seismic experiment that aims to image the Earth's interior. This artwork creatively incorporates indigenous pictograms found in regional rock formations, making a meaningful connection between seismology and the region's rich cultural heritage. Finally, Images of the Silence is an transdisciplany work with scientifics, journalists and artists to develop an unconventional approach to better communicate our results and remind us that science and art always go together.

The deposits of subaqueous dunes are a fundamental building block of verticallystacked alluvium in river to tidal settings and are responsible for producing the largest component of frictional resistance to flow via form roughness. Thus, dunes have attracted considerable attention amongst researchers for decades since they are found in virtually all environments (headland rivers to abyssal plains) and grain sizes (coarse silts to gravels) along the source-to-sink sediment transport pathway. Of these environments, dunes produced by rivers (unidirectional flows) are the most widely studied with respect to their morphologic dynamics and their scaling of height and wavelength to flow depth, whilst our understanding of these same characteristics within bidirectional (tidal) and combined-flow (currents with a unidirectional and oscillatory component) is quite limited. This knowledge gap is addressed herein by evaluating a set of multibeam echo sounding (MBES) surveys of the main channel of the Lower Columbia River (LCR), WA/OR, USA, within its downstream most hydraulic regime, which is dominated by bidirectional tidal-flows and/or combined-flows consisting of a tidal component and a shorter period (oceanic to intrabasinally derived) wind-wave component. Specifically, variations in dune geometric parameters (e.g., height, wavelength, roundness, symmetry, dimensionality, stoss- and lee- angle, and ratio of stoss- to lee- angles) and scaling of height and wavelength to flow depth are systematically quantified within the main channel (0- 32m depth) and are linked to depth transitions in formative current styles. These findings provide insight into the morphologic differences (i.e., form roughness) between dunes generated within non-uniform and unsteady flow conditions and those from more uniform and steady flows, whilst further adding to our understanding of the scaling of height and wavelength to depth within such dynamic flows. Preliminary results show that dunes remain asymmetric at all depths and possess lee-angles ≤ 15°, their roundness is maximized at both the shallowest and deepest depths, and present river-tidal scaling relations overpredict their heights and wavelengths, which suggests that new relations are needed to better understand the dunes of tidal and combined-flow settings.

Mars experienced a dynamo process that generated a global magnetic field ~4.3–3.6 Ga. The cessation of this dynamo strongly impacted Mars’ history and is expected to be linked to thermochemical evolution of Mars’ iron-rich liquid core, which is strongly influenced by its thermal conductivity. Here we directly measured thermal conductivities of solid iron-sulfur alloys to pressures relevant to the Martian core and temperatures to 1023 K. Our results show that a Martian core with 16 wt% sulfur has a thermal conductivity of ~19 to 32 W m-1 K-1 from its top to the center, much higher than previously inferred from electrical resistivity measurements. Our modelled thermal conductivity profile throughout the Martian deep-mantle and core indicates a ~4 to 6-fold discontinuity across the core-mantle-boundary. The core’s efficient cooling resulting from the depth-dependent, high conductivity diminishes thermal convection and forms thermal stratification, significantly contributing to cessation of Martian dynamo.

Large amounts of gas hydrates exist on continental slopes, and pose a significant risk of triggering submarine landslides, subsequently impacting offshore infrastructures. While the infinite slope model is widely used for submarine slope stability analysis, it overlooks the potential for initial small failures to develop into large landslides. Our study integrates slip nucleation with excess pore pressure during gas hydrate dissociation, establishing a model for progressive slope failure triggered by hydrate dissociation. Focusing on the Shenhu hydrate site GMGS3-W19, our results show that even 1% gas hydrate dissociation contributing to about 1 MPa overpressure can induce progressive landslides. Notably, deeper failure surfaces with gentler slopes and collapsible sediments require higher pore pressures to induce progressive failure, reducing the risk of developing into catastrophic landslides. The results indicate that the infinite slope model may overestimate slope stability, and that submarine landslides caused by progressive failure may occur on slopes previously considered stable, such as the Ursa Basin in the northern Gulf of Mexico. This extension of the infinite slope model sheds light on potential limitations in current stability assessments, providing crucial insights for submarine landslide studies and offshore infrastructure development.

While basaltic volcanism is dominate during rifting and continental breakup, felsic magmatism may also comprise important components of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite-garnet-cordierite bearing dacitic, pyroclastic unit was recovered within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring transform margin. Here, we present a comprehensive textural, mineralogical, and petrological study of the dacite in order to assess its melting origin and emplacement. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, highly vesicular, glassy matrix, locally mingled with sediments. The xenocrystic major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support a crustal metapelite origin. While most magma-rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the dacite was produced at upper-crustal depths (< 5 kbar) and high temperature (750–800 °C) with up to 3 wt% water content. In situ U-Pb analyses on zircon inclusions give a magmatic age of 54.6 ± 1.1 Ma, revealing the emplacement of the dacite post-dates the Paleocene-Eocene Thermal Maximum (PETM). Our results suggest that the opening of the North Atlantic was associated with a phase of low-pressure, high-temperature crustal melting at the onset of the main phase of magmatism.

Magnetic hysteresis measurements are routinely made in the Earth and planetary sciences to identify geologically meaningful  magnetic recorders, and to study variations in present and past environments. Interpreting magnetic hysteresis data in terms of domain state (particle size)  and paleomagnetic stability are major motivations behind undertaking these measurements, but the interpretations remain  fraught with challenges and ambiguities. To shed new light on these ambiguities, we have undertaken a systematic micromagnetic study to quantify the magnetic hysteresis behavior of room-temperature magnetite as a function of particle size (50-195 nm; equivalent spherical volume diameter) and shape (oblate, prolate and equant); our models span uniformly magnetized single domain (SD) to non-uniformly magnetized single vortex (SV) states. Within our models the reduced magnetization  marks a clear boundary between SD (≥0.5) and SV (<0.5) magnetite. We further identify particle sizes and shapes with unexpectedly low coercivity and coercivity of remanence. These low coercivity regions correspond to magnetite particles that typically have multiple possible magnetic domain states, which has been previously linked to a zone of unstable magnetic recorders. Of all hysteresis parameters investigated, transient hysteresis is most sensitive to particles that exhibit such domain state multiplicity, leading us to suggest that transient behavior be more routinely measured during rock magnetic investigations.

The ability of rocks to hold a reliable record of the ancient geomagnetic field depends on the structure and stability of magnetic domain-states contained within the rock’s magnetic particles. In paleomagnetic studies, the Day plot is an easily constructed graph of magnetic hysteresis parameters that is frequently used (and mis-used) to estimate the likely magnetic recording stability of samples. Often samples plot in the region of the Day plot attributed to so-called pseudo-single-domain (PSD) particles with little under standing of the implications for domain-states or recording fidelity. Here we use micromagnetic models to explore the hysteresis parameters of magnetite particles with idealized prolate and oblate truncated-octahedral geometries containing single domain (SD), single-vortex (SV) and occasionally multi-vortex (MV) states. We show that these do main states exhibit a well-defined trend in the Day plot that extends from the SD region well into the multi-domain (MD) region, all of which are likely to be stable remanence carriers. We suggest that although the interpretation of the Day plot and its vari33 ants might be subject to ambiguities, if the magnetic mineralogy is known, it can still provide some useful insights about paleomagnetic specimens’ dominant domain state, average particle sizes and, consequently, their paleomagnetic stability.