Plate-like behavior in mantle convection models is commonly obtained using a strongly temperature-dependent viscosity together with a low yield stress that caps lithospheric strength. Yet, alternative mechanisms for limiting strength, including low-temperature plasticity, have been proposed. Here, we investigate how different rheological formulations promote lithospheric-scale strain localization, using 2-D thermo-mechanical simulations of upper mantle extension. We test a suite of olivine flow laws (diffusion creep and dislocation creep at low- and/or high-temperature), with and without a yield-stress cap, and introduce diagnostics that attribute plate weakening to either increasing strain rate (mechanical weakening) or increasing temperature (thermal weakening). Without a yield-stress cap, deformation remains distributed in all cases, indicating that weakening of the whole lithosphere is required for strain localization. In such simulations, a new extensional plate boundary develops in two stages: progressive narrowing of the deforming zone followed by rapid thinning of the weakened lithosphere. Across plate ages of 10–100 Myr, localization depends weakly on age but strongly on divergence rate, primarily through Stage-1 narrowing, and is controlled more by the stiffest lithospheric region than by the presence of a shallow weak layer. Including dislocation creep allows both mechanical and thermal weakening to operate within the deforming plate, enhancing feedbacks and accelerating localization relative to yield-stress plus diffusion creep. This implies that yield-stress/diffusion-only rheologies may overestimate break-up timescales in whole-mantle convection models. Low-temperature dislocation creep weakens the plate at 800–1000 K, providing a physically grounded mechanism for limiting strength in this temperature range. Finally, we propose that thermal weakening may in some cases promote rapid strength loss and accelerated extension during the late stages of natural rift evolution.
Abstract. In the present work, the elastic properties of both 1M and 2M1 phlogopite polytypes, KMg3Si3AlO10(OH)2 (monoclinic crystal system) were investigated from PV equation of state fitting and by analysis of the fourth-rank elastic tensor. The analysis was performed within the Density Functional Theory framework, using all-electron Gaussian-type orbitals basis sets and the B3LYP functional corrected a posteriori to include long-range interactions (B3LYP-D*). In general, the elastic properties of the two polytypes were strongly anisotropic, with the axial moduli ratio M(a) : M(b) : M(c) being close to 4:4:1. The volume-integrated third-order Birch-Murnaghan equation of state fitting parameters at 0 K were K0=57.9(2) GPa, K′=8.29(7) and V0=489.82(3) Å3 for phlogopite-1M, which were very close to those of the 2M1 polytype, i.e., K0=58.3(1) GPa, K′=8.71(8) and V0=978.96(9) Å3. The monoclinic elastic tensors obtained for the two polytypes of phlogopite, which have never been experimentally reported for both minerals so far, were in line with the PV behaviour of the mineral, providing further data related to the directional dependence of the elastic properties and seismic wave propagation. The elastic properties from both PV hydrostatic compression and from the elastic moduli tensor were discussed against the available experimental and theoretical data in the scientific literature, extending the knowledge on this important trioctahedral phyllosilicate.
Gas hydrates and deltaic deep-sea fans are main features in continental margin systems, influencing slope stability, fluid migration, and carbon cycling. In the northwestern Black Sea, the Danube Fan remains poorly constrained with respect to subsurface structure, sediment strength, and hydrate dynamics. Here, we present high-resolution multichannel seismic (MCS) and ocean-bottom seismometer (OBS) data to characterise sedimentary structure and fluid-related features. Two integrated OBS–MCS profiles reveal under-consolidated, clay-rich levee deposits interspersed with mass-transport units, chaotic facies, and gas-related anomalies. Derived P- and S-wave velocity models indicate low shear strength and high Vp/Vs-ratios in shallow units, consistent with soft, water-saturated sediments. Deeper layers display compaction-driven velocity increases but remain mechanically weak, rendering the slope prone to failure. Our findings suggest that vertical gas migration is widespread, expressed by seismic chimneys, polarity reversals, and velocity pull-downs, with free gas confined below bottom simulating reflectors and in stratigraphic traps. Hydrates likely occur as sparse, patchy pore-filling accumulations, and the lack of S-wave velocity anomalies suggests they do not act as cementing phases, implying little direct influence on sediment strength or slope stability. The hydrate system appears hydrate-poor, possibly reflecting post-glacial re-equilibration. Overall, lithology, gas migration pathways, and high sedimentation rates emerge as primary controls on hydrate formation and slope instability in the Danube Fan.
Brunia is a distinctive crustal block within the European Variscides, composed of a late Neoproterozoic arc complex overlain by Ediacaran-early Cambrian cover sequences. Sparse preservation of early Paleozoic strata obscures its pre-Variscan paleogeography. Proposed models suggest Brunia either shared a crustal domain with adjacent parts of the Bohemian Massif, represented a far-eastern extension of Avalonia accreted to Baltica in the early Paleozoic, or maintained long-term connections to Baltica since the late Ediacaran.To address these uncertainties, we present the first systematic study of detrital zircons (both U-Pb and Lu-Hf isotopic data) from Devonian strata overlying Brunia's Neoproterozoic basement. Two distinct age-spectral patterns are identified. Type-1, widespread across Brunia, exhibit a near-unimodal late Neoproterozoic peak corresponding to locally preserved arc magmatism. Type-2, display a multimodal spectrum with significant Late Ordovician-Silurian and Paleoproterozoic-early Neoproterozoic age peaks, and only minor late Neoproterozoic input.The Type-1 pattern reflects predominant recycling of local Brunia sources. Nearly-uniformly positive epsilon Hf(t) values in Neoproterozoic zircons contrast with the wide isotopic range typical of other Variscan terranes in Central and Western Europe, but are comparable with values from Avalonian strata in Newfoundland, supporting a Neoproterozoic link between West Avalonia and Brunia.The Type-2 pattern broadly matches Devonian detrital zircon signatures from the British Isles, the Rhenish and Harz Mountains and parts of the Mid-German Crystalline Rise, the Dobrogea region of Romania, and NW Turkey delineating the northern margin of the Rheic Ocean. Strong similarity to Ordovician-Silurian Scandinavian datasets suggests original derivation from the Caledonides and confirms an Early Devonian connection between Brunia and Baltica.
Correlating late coda waves from large earthquakes produces stable waveforms that approximate inter-station core phases. However, the properties of these coda waves often violate the strict assumptions underlying classical Green's function retrieval, undermining confidence in interpreting the reconstructed arrivals as true inter-station phases and limiting their utility in seismic imaging. In this study, we present a perturbation analysis of core-phase interferometry and show that accurate travel-time information can be recovered under locally uniform wave incidence along the inter-station path. We introduce a dimensionless parameter - defined as the ratio of the seismic wave period to the inter-station travel time - which establishes a critical angular threshold. Our perturbation analysis reveals that the travel-time reconstruction accuracy scales with the cube of this threshold, allowing high-precision recovery of core phases, which naturally exhibit small threshold values due to their long propagation paths. Numerical simulations validate the theoretical predictions. By applying the proposed framework to real coda correlation data, we demonstrate that core phases can be reliably reconstructed using a sufficiently large number of global earthquakes - even without the traditionally assumed uniform source distribution. These results establish a rigorous theoretical foundation for extracting high-precision core-phase travel times from coda correlations, enhancing the reliability of seismological imaging of Earth's deep interior.
The deep, high-resolution regional-scale seismic profiles of the PolandSPAN (R) survey provided a unique insight into the extensive system of inferred igneous intrusions imaged within the crystalline basement of the Baltic Basin (SW part of the East European Craton). These intrusions, that continue laterally for 100+ km, are located at depth of ca. 6-7 to 19-20 km, and are far beyond the reach of the deepest wells. They are represented by packages of strong seismic reflectors, sometimes saucer-shaped, and are often characterized by step-wise geometry, sometimes diverging into several separate branches. Forward seismic modelling was used in order to provide insight - "educated guess" - regarding their lithology, exact lateral extent, and lateral thickness variations. It was concluded that most probably these are doleritic intrusions of thickness in the range of 60 to 200 m. Due to lithological coherence and close spatial relation to shallow sills and massifs recognized in wells, they have been interpreted as Mississippian (early Carboniferous) intrusions belonging to the recently recognized Lublin-Baltic Igneous Province. We applied a methodology that combines quantitative assessment of seismic data resolution and estimation of tuning thickness with 2D seismic forward modelling based on geological constraints that may be used to better understand, or estimate, parameters characterizing deep intrusions that are beyond the reach of deep wells.
We analyze the statistical characteristics of non-volcanic tremor (NVT) sequences in the Mexican subduction zone. To this end, we employ various techniques, including the Gutenberg-Richter relationship, non-extensive statistics, and multifractal detrended moving-average analysis, to extract information on magnitude and interevent-time distributions. The b-value results reveal that b ranges from 1.25 to 2.42, with the highest values occurring in the down-dip portion of the plate interface. In contrast, the q-value shows an inverse behavior, reaching its highest values in the interplate coupling region. Similar to tectonic earthquakes, NVT sequences exhibit a multifractal structure in both magnitude and interevent-time series. The multifractality analysis suggests that this behavior is associated with long-term correlations, the probability distribution of the data, and nonlinear dynamics. Both apparent and intrinsic multifractality are identified, with the former being dominant. Our estimates of the Hurst exponent (H) range from 0.65 to 1.06; most sequences indicate strong persistence (H>0.95), while values exceeding unity suggest a transition toward non-stationary behavior. These high temporal correlations may reflect localized fluid-perturbed regions, although this interpretation remains speculative. Regarding the distribution that best describes interevent sequences, we find that most sequences are well described by a Lognormal distribution and, to a lesser extent, by a Gamma distribution. Finally, observations of tectonic tremor duration exhibit substantial scatter, resulting in low coefficients of determination in scaling relationships. The source of this variability may be related to the NVT generation mechanism or to detection and characterization processes.
We present updated estimates of Basic Earth Parameters (BEP) from VLBI Celestial Pole Offset (CPO) time series spanning 1980-2025 using an ensemble Markov Chain Monte Carlo (MCMC) Bayesian inversion. Building upon , we incorporate recent advances in ocean tidal modeling and update several aspects of the algorithm. Key improvements include: (1) implementation of a cubic spline representation for Free Core Nutation (FCN) amplitude variations, which significantly reduces multimodality in FCN-related parameter in MCMC sampling compared to a linear representation; (2) integration of updated Ocean Tidal Angular Momentum (OTAM) values from FES2014 ocean tidal atlas , without the empirical 0.7 scaling factor previously applied in the construction of the last adopted nutation model MHB2000; and (3) utilization of five diverse CPO series from different analysis centers spanning up to 45 years of observations. Our estimated mean values of the parameters show good consistency across different CPO series, with values of the Earth's dynamical ellipticity at the edge of the 1 sigma range of MHB2000 . Notable findings include a larger absolute value for the imaginary part of the core-mantle boundary (CMB) coupling constant ( K CMB ), approaching the 2 sigma boundary of , which may reflect contributions from other coupling mechanisms in addition to electromagnetic coupling, including possible topographic coupling through "form drag" effect caused by wave interactions with irregular boundaries . The real part of the Inner Core Boundary (ICB) coupling constant ( K ICB ) is approximately half the MHB2000 value, potentially indicating the need to revisit hydrostatic assumptions for the inner core given recent seismic evidence of viscous deformation . Compliance estimates suggest that frequency extrapolation methods from seismic to nutation bands may be considered unchanged in the mantle, but should be revised at the ICB. The enhanced FCN free-mode modeling captures amplitude variations that differ from empirical models, particularly after 2000, although the physical interpretation of these differences requires further investigation. The systematic discrepancies across multiple parameters suggest that current nutation theory needs substantial updates to incorporate more realistic models of core-mantle coupling and inner-core-outer-core coupling.
Remote sensing and field data suggest distributed right-lateral faulting at the northern edge of the Quito-Latacunga microblock in northern Ecuador and southern Colombia. Off the west coast of Ecuador and Colombia, oblique subduction of the Nazca Plate beneath the South America plate induces NE-motion of the Northern Andean Sliver relative to stable South America. Recent geodetic studies show this sliver comprises several independent microblocks, with strain accommodated at each of their boundaries. The Quito-Latacunga microblock, located in the densely populated Inter-Andean valley, shows approximately 3 mm yr−1 of right-lateral strain at its northern boundary. However, which structures accommodate this deformation is unclear. Using available digital terrain models (DTMs), local DTMs derived from Pleiades satellite stereo-imagery, InSAR, Google Earth imagery, and field surveys, we demonstrate deformation at the northern boundary is distributed across several NE-striking right-lateral faults in Ecuador and Colombia. InSAR shows that a recent 2022 M 5.6 earthquake resulted in line-of-sight displacement of 5 to 13 cm along one of the ENE-striking, right-lateral faults. Offset sediments and glacial features indicate recent earthquakes on two other faults (the Reservoir and Polylepis faults) north of and subparallel with this rupture. Displaced glacial landforms along the Reservoir fault show slip rates between 0.8 and 6.1 mm yr−1, suggesting geologic slip rates that could be higher than geodetic ones. Exposures of the Reservoir fault also show evidence for at least three surface rupturing earthquakes with magnitudes between M 6.3 and M 7.0. Inflation at the nearby Chile-Cerro Negro volcano may influence earthquakes on these faults, enhancing slip and earthquake rates. The Polylepis, Reservoir, and 25 July earthquake faults all overlap with the proposed area for the 15 August 1868, M 6.4–6.8 El Angel earthquake, indicating they could be associated with this damaging event.
The Carpathian Region, located at the edge of the East European Platform, presents a unique tectonic setting where major deformation associated with subduction and collision appears to have ceased around 8 million years ago. Yet vertical movements and seismicity continued afterward till the present day, suggesting ongoing crustal deformation and challenging our understanding of intraplate earthquakes and the processes driving these phenomena in an area considered a stable continental interior. In this study, we analyze over two decades of continuous GPS (cGPS) data from 143 permanent stations to estimate both horizontal and vertical crustal motions, constructing the most accurate model of crustal deformation in the region to date. The estimated velocity field indicates a southward drift of the South Carpathians and Moesia relative to Eurasia, with velocities ranging from 0.5 to 2 mm yr(-1). We detect a more complex pattern of vertical uplift and subsidence in the foredeep, challenging a previously held view that this region is solely subsiding. This pattern may reflect localized uplift in response to processes such as the Vrancea Slab break-off beneath the South-East Carpathians. Crustal-scale active faults accommodate the observed differential motion, fragmenting the foreland. Furthermore, using a regularized horizontal velocity vector field, we estimate strain rate variations, maximum shear strain, and dilatation patterns across Romania, which align with observed stress regimes and earthquake mechanisms. This agreement validates our results and indicates an influence of surface plate kinematics on the observed seismicity, in addition to the deep Vrancea Slab dynamics. Our findings provide insights into the causes of crustal deformation at the transition between active collision zones and stable continental platforms, enhancing our understanding of intraplate seismicity in regions traditionally considered tectonically stable.
We investigated the crustal structure beneath the Lerma Valley in northwestern Argentina using data from a local seismic network deployed between 2017 and 2018. This geologically complex transition zone between the Eastern Cordillera and the Sierras Subandinas is characterized by moderate to high seismicity (INPRES, 2024), yet remains largely understudied despite its strategic location within the Andean orogen (Jordan et al., 1983; Allmendinger et al., 1997). Its passive orogenic setting and evidence of inherited structures (Ramos, 2008; Mon and Salfity, 1995; Kley and Monaldi, 2002) make it a natural laboratory for exploring intraplate deformation and foreland basin evolution (P & eacute;rez et al., 2016; Tassara et al., 2018). We combined local and teleseismic receiver functions with ambient noise tomography (ANT), jointly inverting Rayleigh wave phase velocities to obtain 1D shear-wave velocity profiles. The results reveal a stratified crust with four main discontinuities at similar to 53-43, 35-30, 10-8, and 1.5-1.2 km, corresponding to the Moho, mid- and lower-crustal boundaries, and the base of the sedimentary basin. A southward-dipping Moho is evident from CCP migration and T-component phase shifts. Velocity profiles also show a north-south contrast: lower velocities (1-2.5 km/s(-1)) in the south indicate thicker, less consolidated sediments, while the north exhibits more competent crust (up to 3.5 km/s(-1)). The final model comprises five layers, including three sedimentary and two crystalline crustal units. We also introduced a layer-dependent kappa correction, revealing a trend from 1.65 at the Moho to 2 in upper layers. These results provide new geophysical constraints on the crustal architecture and tectonic evolution of this underexplored Andean region.
Knowledge of the present-day stress field of the Earth's crust is essential for understanding geodynamic processes, as well as for the exploration and management of georeservoirs. The World Stress Map (WSM) project provides the only open-access global database of crustal stress information. To mark the project's 40th anniversary, the WSM database has been substantially updated, and now contains more than twice the number of data records on the orientation of maximum horizontal stress (SHmax) in comparison to the previous release in 2016. The new database includes 100 842 quality-ranked data records documenting the SH(max )orientation in the Earth's crust. As stress data records are clustered around plate boundaries and in sedimentary basins, we provide mean SH(max )orientation estimates on regular global grids of 2, 1, 0.5 and 0.2 degrees using search radii between 50 and 500 km to facilitate the analysis of stress patterns. The results reveal that in intraplate regions, where stress data density has increased significantly, the earlier hypothesis that plate boundary forces and relative plate motion primarily control the SHmax orientation needs to be revised. The SHmax orientation rotates in some areas by more than 50 degrees over spatial scales of 50-500 km. Two notable examples include an similar to 50 degrees rotation of the SHmax orientation in the Alpine foreland, from N-S in the East to NW-SE in the West, and SHmax orientation rotations > 50 degrees over distances of less than 100 km in eastern Australia.
Deep seismic reflection is a key method for investigating plate tectonics, as it enables detailed imaging of lithospheric structures - particularly within the crust and upper mantle. It plays a crucial role in understanding crustal evolution and identifying mineral enrichment zones. However, during data acquisition, deviations from the planned shot and receiver locations often occur due to surface constraints or other logistical challenges. These deviations result in irregular seismic data that can introduce significant migration artifacts during processing, ultimately reducing data quality and hindering the interpretation of deep geological structures. To address this issue, we evaluated four data regularization strategies based on anti-aliasing Matching Pursuit Fourier Interpolation using a 2D deep seismic reflection dataset from the central Jiangnan Orogenic Belt. Among these, the method that involves regularizing and infilling shot gathers at 100 m intervals produced the most effective results. Compared to legacy contractor-processed data, this method achieved a higher signal-to-noise ratio and improved seismic resolution. The superiority of that method was further confirmed through enhanced imaging in the pre-stack time migration results. These findings highlight the importance of shot domain regularization prior to migration in deep seismic reflection surveys.
The geometry, deep structural style, and seismotectonic setting of the outer Abruzzi thrust system are less understood than those of other segments of Italy's Late Pliocene-Quaternary contractional belt. This knowledge gap arises from the region's complex surface geology, low seismicity rates, and the limited resolution of existing geophysical data.Here, we present a local earthquake tomography of a large and previously unexplored area that encompasses the Abruzzi thrust system and spans from the Apennine extensional province in the west to the foreland strike-slip province in the east. The model is based on the inversion of 42 176 P-wave and 29 045 S-wave arrival times from earthquakes with ML ranging from 0.2 to 5.5.Our results show low seismic velocities at upper crustal levels in the western sectors, correlating with continental basins of the extensional domain. In contrast, marked Vp inversions (decrease in velocity with depth) at mid- to lower-crustal depths in the eastern sector delineate a crustal doubling.We interpret the tomographic results in the context of geological, geophysical, and seismological data to construct a 3D conceptual model of the region. This includes the geometric reconstruction of the Abruzzi Arc basal thrust, an eastward convex arcuate structure extending similar to 170 km and reaching depths of similar to 24 km. The model also incorporates strike-slip faults in the footwall and east-dipping normal faults to the west.The structural affinity between the Abruzzi Arc basal thrust and other seismogenic structures of the Padan-Adriatic belt, located in the same structural position, suggests potential seismogenic behavior, although slow deformation rates and long recurrence intervals obscure its seismic expression. This conceptual model provides new insights into regional geodynamics and has significant implications for seismic hazard assessment in the central-southern Apennine transition zone.
Deep (> 4500 m) and ultra-deep (> 6000 m) sandstone reservoirs hold great potential for hydrocarbon resources, yet complex geological challenges hinder the successful exploitation of oil and gas. Fractures in deep and ultra-deep sandstones are prevalent and significantly enhance rock permeability, and critically impact fluid flow and hydrocarbon productivity. Relationships between geological factors and fracture distribution in deep sandstone reservoirs, despite its significance, have remained poorly understood. This study utilizes core, thin section, acoustic emission tests and geophysical well logs to elucidate the interplay between geological elements and fracture occurrences in tight sandstones of the Kuqa Depression, which is a tectonically active foreland basin. The controls of sedimentation, sandbody distribution and earth stress on fracture distribution are analyzed. The research then unravels the effects of lithology units, earth stress fields, and broader tectonic context on fracture distribution patterns. Geological factors, including sedimentary factors (lithology, sandbody thickness and sandbody distribution), earth stress, and tectonic structure are integrated to comprehensively evaluate the fracture distributions in Kuqa Depression. The different lithologies are identified, and fractures in different lithologies are characterized. High-angle fractures and vertical fractures are the main fracture types in Bozi-Dabei area. Fracture density exhibits an inverse relationship with sandbody thickness. The presence of thinner sandstones in conjunction with thin mud layers facilitates the formation of fractures. Paleostress affects the generation of natural fractures, and high fracture density is associated with high paleostress magnitudes. In situ stress affects the subsequent modification of natural fractures. However, some filled fractures with wider aperture oriented at high angles to SHmax reveal cement-stress interactions jointly controlling apertures, not stress dominance. Structure factors including the position at folds and the proximity to faults are crucial for the fracture distribution. Fractures are more abundant in the hinge areas of anticlines compared to the limb areas, and fracture density above the neutral planes is notably higher. In addition, fracture density is higher in the formation adjacent to the fault due to the effect of the regional stress field. This study helps unravel the geological controlling factors and distribution of fractures by integrating geological and geophysical data, and has implications for hydrocarbon resource exploration in deep and ultra-deep sandstones.
In subduction zones, the accretionary wedges play a vital role in mediating the burial processes of incoming oceanic sediments and eventually their return pathways to the surface. A direction of the previous tectonic models invoked the standard corner flow theory, assuming a slab-parallel shear and a rigid, fixed overriding plate, to elucidate the crustal recycling processes in tectonic wedges. To deal with more complex subduction-collisional settings, where they have deformable overriding plates, and associate a horizontal slab migration (advance or rollback) component during subduction, we develop a generalized corner flow model to revisit the problem of return flow mechanics, providing a criticality analysis of the return flows as a function of the geometric, kinematic, and rheological conditions in accretionary wedges. A new set of analytical solutions is presented to evaluate the limiting conditions in which a wedge can set in significant return flows, leading to focused exhumation of the deep-crustal materials. The theoretical results suggest that, for moderate wedge-taper angles (similar to 30 degrees), the viscosity ratios (mu r) between the overriding plate and the wedge >=similar to 103 provide favourable tectonic settings for the return flow kinematics in accretionary wedges. Decrease in mu r, or addition of slab roll back weakens the return flows, whereas slab advance greatly strengthens the return flows. The analytical solutions are also utilized to demonstrate reversals in the shear-sense patterns across the wedge. We expand this study by incorporating results from scaled laboratory experiments to evaluate applicability of the generalized theoretical model. It is shown from the theoretical model that the total pressure in the accretionary wedge dynamics becomes close to the lithostatic value when the rheological setting has low-viscosity (1019 Pa s) wedge materials.
Analysing the spatial arrangement, connectivity, and evolutionary history of complex fault networks is essential for quantifying strain distribution in active deformational zones, and evaluating associated geohazard and resource potentials. The structure and evolution of fault networks are commonly investigated using a range of methods, including the analysis of topographic data derived from satellite imagery, numerical modelling, as well as physical experiments. The high density and intrinsic complexity of fault systems in many study areas or models pose significant challenges for automated analysis, often necessitating time-intensive manual interpretation. Here, we present Fatbox, the Fault Analysis Toolbox, an open-source Python library that integrates semi-automated fault extraction with automated geometric and kinematic analysis of fault networks. The toolbox capabilities are demonstrated through three case studies on normal fault systems, each drawing on a different data type: (1) fault extraction and geometric characterization using GLO-30 topographic data in the Magadi-Natron basin in East Africa; (2) spatio-temporal tracking of fault development in vertical cross-sections of a forward numerical rift model; and (3) surface fault mapping and geometric evolution of a physical rifting experiment. Fatbox represents fault networks as topological graphs, comprising nodes (i.e., points) and edges (i.e., lines) connecting the nodes. In time-dependent models, the toolbox enables temporal tracking of faults, providing detailed insights into their geometric evolution and facilitating high-resolution measurements of fault kinematics. Fatbox offers a versatile and scalable framework that enhances the efficiency, reproducibility, and precision of fault system analysis - opening new avenues for tectonic research.
The volume increase that accompanies many hydration reactions can stress and fracture the surrounding rock, a process commonly called reaction-induced fracturing. Reaction-induced fracturing accelerates the rate of hydration by creating new pathways for fluids to migrate into reactive rock and by generating new reactive surface areas. The evolution of reaction-induced fractures also depends on the background stress state, which varies among different tectonic environments. We investigate the impact of tectonic stresses on reaction-induced fracturing using 2-D hydraulic-chemical-mechanical distinct element models. The results indicate that the general pattern of reaction-induced fractures depends on the orientation of background tectonic stresses relative to fluid-supplying channels. A spalling fracture pattern characterized by short cracks parallel to and along fluid-supplying channels occurs when the maximum principal tectonic stress is parallel to the channels whereas a branching fracture pattern characterized by long tensile cracks that propagate in a hierarchical manner into unreacted parts of the rock is expected when the tectonic stress is hydrostatic or when the maximum principal tectonic stress is normal to fluid-supplying channels. Spalling localizes hydration and fluid flow along the channels whereas branching promotes spatially extensive hydration and fluid flow away from the fluid supply. The results indicate tectonic stresses may guide the hydration distribution in the oceanic lithosphere at mid-ocean ridges and outer rises and in the cold mantle wedge corner in subduction zones.
We present TCSEIS-1D, a software to model the Earth's thermochemical and geophysical structure from the surface down to the core-mantle boundary (CMB). The code is designed to estimate geophysical parameters of the Earth's crust and mantle from petrological and thermal information within a thermodynamically consistent framework and to perform forward 1D coupled geophysical-petrological modelling of the structure of the Earth. Developed in Julia Language, the open-source code is intended to be an easy-to-use, flexible, and fast. TCSEIS-1D includes tools to exploit the large repertoire of 1D seismological data available, namely: surface wave dispersion curves (of fundamental and higher modes of Rayleigh and Love waves) and receiver functions (of P, S, and SKS waves). Surface heat flow and isostatic topography can also be modelled. Four simple examples that illustrate the capabilities of the code are presented to show the sensitivity of Rayleigh wave phase velocity curves and P-to-S receiver functions to compositional and temperature variations.
