Journal of Geophysical Research: Solid Earth最新文献

{"title":"Global Presence and Absence of Ultra-Low Velocity Zones as Seen by Sdiff Postcursors","authors":"J. R. Atkins, C. Martin, S. Cottaar","doi":"10.1029/2025jb033171","DOIUrl":"https://doi.org/10.1029/2025jb033171","url":null,"abstract":"The core-mantle boundary (CMB) is a region of significant lateral heterogeneity. Two antipodal large low-velocity provinces (LLVPs) dominate the lower mantle, while smaller but more extreme ultralow velocity zones (ULVZs) are scattered atop the CMB in a variety of morphologies. These ULVZs have been linked to both the edges of LLVPs and to plume-related hotspots, the latter of which may plausibly be fed or anchored by ULVZs. In this study, we produce a global map of ULVZs using the phase S_diff, an S-wave that diffracts along the CMB. We hand-pick over 2 million traces and detect nearly 100,000 postcursors to S_diff and over 900,000 robust null observations, achieving 99.8% coverage of the CMB. Nearly all regions of S_diff postcursor presence can be explained by six “S_diff-ULVZs”, which are found to preferentially lie both underneath hotspots and near LLVP edges. There could exist multiple types of ULVZs, and those large-scale ULVZs that S_diff are sensitive to are linked to some hotspots and the edges of LLVPs, while others may not be. Notably, we find that the large majority of the CMB lacks evidence for the presence of large-scale ULVZs.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"34 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147753408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dilatant Strengthening in Fluid-Saturated Thermally Cracked Westerly Granite: Competing Effects of Strain Rate and Fluid Diffusion","authors":"Gang Lin, Caiyuan Fan, Samuel Chapman, Jérôme Fortin, Alexandre Schubnel","doi":"10.1029/2025jb033235","DOIUrl":"https://doi.org/10.1029/2025jb033235","url":null,"abstract":"The interplay between the strength of crystalline rocks and fluid diffusion is fundamental to the dynamics of the crust and that of fault systems. We measured the strength of thermally cracked Westerly granite as a function of strain-rate, confining pressure and fluid pressure. Experiments were conducted at the same initial pore fluid pressure with either nominally drained or undrained boundary conditions. The samples internal pore pressure was measured with pressure transducers attached to the surface of the samples. A systematic decrease in the internal pore pressure was observed when approaching peak stress, leading to an increase in the effective stress and strength of the samples. Although peak brittle strength increased with strain-rate, it remained consistent with a simple Mohr-Coulomb failure criterion when calculating the effective stress from the internal pore pressure. Performing additional experiments with undrained boundary conditions revealed that the Mohr-Coulomb envelope could be determined from a single experiment, demonstrated by the stress trajectory being almost tangential to the failure criterion during the final stage of the experiment. Finally, we demonstrate that the onset of dilatant strengthening (and pore pressure drop) was reached for a critical volumetric (dilatant) strain rate. Because of the competition between fluid diffusion and dilatancy, this critical volumetric strain-rate, derived through dimensionless analysis, is proportional to permeability, and consequently, exhibits pressure dependence. Overall, our results are summarized with a simple conceptual model, where the brittle strength is bounded by the drained (lower) and undrained (upper) limits, the transition between both being permeability and strain-rate dependent.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"65 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147726458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Electrical Conductivity of the Lower Mantle From High-Pressure/High-Temperature Measurements of Pyrolite and Ten Years of Geomagnetic Observations","authors":"Charlotte Trubowitz, Motohiko Murakami, Federico Munch, Alexander Grayver, Christian Liebske, Amir Khan, Nobuyoshi Miyajima, Pinku Saha, Yoshiyuki Okuda, Georg Spiekermann, Luiz Grafulha Morales","doi":"10.1029/2025jb032837","DOIUrl":"https://doi.org/10.1029/2025jb032837","url":null,"abstract":"Electromagnetic sounding coupled with experimental measurements of electrical conductivity (EC) can provide valuable constraints on the thermochemical state of Earth's lower mantle. Here, we report a new set of experimentally determined EC values of pyrolite, a candidate composition of the lower mantle, between 25 and 80 GPa at room temperature and high temperature between 1,200 and 2,300 K using a laser-heated diamond anvil cell combined with impedance spectroscopy. To maintain and better constrain the geometry of the experimental assembly, we used focused ion beam-cut discs of a pre-synthesized pyrolitic sample. Our results reveal a monotonic increase in EC with pressure, in contrast to earlier measurements that suggested a spin-transition-induced conductivity drop in the mid-lower mantle. We also identify intrinsic voltage- and pressure-related time-dependent behavior that are likely expressions of nonlinear grain-boundary conduction and stress-driven relaxation processes, respectively. To our knowledge, this is the first report of such behavior in geological materials and may represent a previously unrecognized source of uncertainty in earlier high-pressure EC data sets. Finally, we compare predictions based on our experimental findings against the radial EC structure derived from analysis of 10 years of satellite magnetic data from the ESA Swarm mission, with improved resolution in the lower mantle down to 2,200 km. We find that the measured EC of pyrolite is consistent with the geophysically inferred conductivity structure.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"9 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147753417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High Geomagnetic Reversal Frequency During the Middle to Late Ediacaran (∼570 Ma) Constrained by Integrated Magneto- and Cyclostratigraphy","authors":"J. W. L. Afonso, R. M. Rocha, D. R. Franco, N. B. Dos Santos, C. G. Leandro, P. Franceschinis, A. E. Rapalini, M. J. Arrouy, L. E. Gómez-Peral, D. G. Poiré, S. Caetano-Filho, H. D. Brito, R. I. F. Trindade","doi":"10.1029/2025jb033554","DOIUrl":"https://doi.org/10.1029/2025jb033554","url":null,"abstract":"The Ediacaran–Cambrian (∼635–539 Ma) geomagnetic field is characterized by unusually high reversal rates and markedly weakened field strength. Estimates of these reversal frequencies can reveal key aspects of deep Earth dynamics and their potential influence on surface environments and early complex life. Here, we present a constraint on geomagnetic reversal rates at ∼570 Ma by integrating previously acquired magnetostratigraphic data and cyclostratigraphic analyses from three drill cores (E7, E34, and H9) of the Ediacaran Avellaneda Formation (La Providencia Group, Argentina). Cyclostratigraphic analysis was conducted using a grayscale series derived from sediment color, which captures compositional variability linked to marl–limestone and claystone–limestone alternations. Time-series analyses identified a complete hierarchy of orbital cycles above the 95% confidence level, and whose period ratios closely match those expected at ∼570 Ma. The optimal sedimentation rate estimate of 0.9–2.2 cm kyr⁻¹ supports the interpretation of Milankovitch-driven cyclicity. Using a Gaussian bandpass filter, we isolated the 100 kyr cycle bands to construct a floating astronomical timescale for the Avellaneda Formation. Cyclostratigraphic calibration yields estimated durations of 850 ± 56 kyr (core E7), 900 ± 37 kyr (core E34), and 1,000 ± 85 kyr (core H9), which imply constrained reversal frequencies of approximately 7–11reversals per million years. Our results confirm the hyperactive geomagnetic reversal regime during the late Ediacaran. Moreover, these findings contribute to understanding the evolution of the geodynamo and its broader implications for the co-evolution of Earth's interior, atmosphere, and biosphere during a critical interval of Earth's history.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"54 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147726459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Restricted Crustal Extrusion in Eastern Tibet Plateau: Insight From Anisotropic Q Tomography of Lg Wave","authors":"Jing He, Qingju Wu, Eric Sandvol, Mijian Xu","doi":"10.1029/2025jb032944","DOIUrl":"https://doi.org/10.1029/2025jb032944","url":null,"abstract":"Crustal rheology is crucial for understanding crustal deformation and block interaction during the eastward expansion of the Tibetan plateau. The presence of significant structural boundaries and fault zones in eastern Tibet complicates the determination of primary factors contributing to high crustal attenuation. It remains unclear whether this attenuation is due to scattering resulting from seismic heterogeneity or intrinsic absorption from anelasticity. In this study, we perform azimuthal anisotropy crustal attenuation tomography using Lg waves to invert for the isotropic <i>Q</i> values (<i>Q</i>_iso), anisotropic <i>Q</i> values (<i>Q</i>_ani), and the high-<i>Q</i> directions in eastern Tibet. The widespread low <i>Q</i>_ani values indicate significant azimuthal-dependent attenuation in the Tibetan Plateau, suggesting strong heterogeneity in the crust. Prominent low <i>Q</i>_iso zones within the Songpan-Ganzi block are constrained by major faults, indicating that crustal faults restrict the crustal extrusion of the plateau. Within the inner zone of the Emeishan-large-igneous-province (ELIP) and along the eastern margin of the plateau, the high <i>Q</i>_iso values indicate low intrinsic attenuation, implying strong crustal rheology. These rigid regimes with strong rheology hinder the southeastward extrusion of the Tibetan Plateau, characterized by weak crustal rheology. Extremely low <i>Q</i>_iso values found in the intermediate zone of the ELIP near the Xiaojiang fault imply weak mechanical strength of the crust. We propose that the presence of the <i>α</i>-<i>β</i> quartz phase transition exacerbates this high crustal attenuation associated with partial melting in the crust.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"54 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147753436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variable Oceanic Crust Accretion at a Slow-Spreading Ridge: A Vp/Vs Ratio Evidence Across the Southwest Sub-Basin of the South China Sea","authors":"Ye Yuan, Yuhan Li, Yongjian Yao, Minghui Zhao, Jiazheng Zhang, Enyuan He, Lianjun Li","doi":"10.1029/2025jb033112","DOIUrl":"https://doi.org/10.1029/2025jb033112","url":null,"abstract":"The opening of the Southwest Sub-basin (SWSB) of the South China Sea was slow-spreading and has been propagated toward the southwest. Yet, the structural variability and magmatic accretion process of the SWSB are still enigmatic. Here, utilizing a wide-angle seismic profile traversing the central segment of the SWSB, we obtain detailed S-wave velocity and V_p/V_s ratio models to investigate oceanic accretion process. In the first stage of seafloor spreading (ages &gt;19.2 Ma), the V_p/V_s in the northern conjugate flank is more variable, while the V_p/V_s in the southern flank is lower and more convergence, with V_p and V_s decreased, indicating more vigorous magmatism on the northern flank but more thick cracks developed on the southern flank. In the second stage of spreading (ages ∼19.2–17 Ma), V_p/V_s ratios in different conjugated flanks indicate pronounced asymmetry in oceanic lithospheric structure. The V_p/V_s ratios in the southern flank reveal a partially serpentinized mantle overlain by possible continental fragments embedded in basaltic rocks, contrasting to the normal oceanic crust in the north. Our results suggest that magmatic budget in the SWSB during seafloor spreading was asymmetric and consistently stronger in the north flank of the spreading axis, which probably associated with a southward ridge jump event. The high V_p/V_s ratios at the extinct spreading center reveal the serpentinization beneath both flanks of the median valley. After the cessation of seafloor spreading, the tectonic extension of the frozen magma chamber formed a median valley composed of highly fractured mafic rocks overlain by remnant continental fragments.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"1 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147753411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rapid Earthquake Magnitude Estimation for Local Early Warning Systems Using Seismogeodesy","authors":"Jonatan Glehman, Yehuda Bock, Barry Hirshorn, Allen Nance, Jonathan R. Weiss, Stuart Weinstein, Dorian Golriz","doi":"10.1029/2025jb033222","DOIUrl":"https://doi.org/10.1029/2025jb033222","url":null,"abstract":"Rapid and accurate estimation of earthquake moment magnitude is crucial for early warning systems, for alerting coastal populations vulnerable to tsunamigenic hazards. Most seismic-based estimation approaches introduce time delays that limit applicability near the source, while geodetic approaches have been limited to empirical scaling relationships. We extend a physics-based approach for seismogeodetic moment magnitude (&lt;i&gt;M&lt;/i&gt;&lt;sub&gt;&lt;i&gt;wg&lt;/i&gt;&lt;/sub&gt;) estimation initially developed for thrust earthquakes to also include strike-slip and normal fault mechanisms by examining 17 &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;&lt;i&gt;w&lt;/i&gt;&lt;/sub&gt; 7.0 to 9.1 earthquakes. We find that considering S-wave propagation is critical for accurately estimating the magnitude of strike-slip events. Radiation pattern (RP) corrections offer substantial benefits for normal fault events but are difficult to compute in real-time. However, RP corrections can be neglected for strike-slip events, while thrust and normal earthquakes are more reliably handled using the previously established seismogeodetic approach, allowing accurate &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;&lt;i&gt;wg&lt;/i&gt;&lt;/sub&gt; estimates within about 2–3 min of earthquake initiation in early warning scenarios. We further broaden the seismogeodetic approach by interpolating coseismic windows from collocated GNSS and/or accelerometer stations to stand-alone GNSS stations, thereby increasing the size and geometry of the available network. We present an integrated workflow for rapid &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;&lt;i&gt;wg&lt;/i&gt;&lt;/sub&gt; estimation that leverages tectonic information from subduction-zone geometry to inform focal mechanism selection, rather than relying on uncertain hypocentral depths. Our extended approach provides rapid earthquake magnitudes (∼2–3 min after earthquake initiation) for moderate to large events (&lt;i&gt;M&lt;/i&gt;&lt;sub&gt;&lt;i&gt;w&lt;/i&gt;&lt;/sub&gt; ≥ 7) with an &lt;i&gt;M&lt;/i&gt;&lt;sub&gt;&lt;i&gt;wg&lt;/i&gt;&lt;/sub&gt; accuracy of &lt;span data-altimg=\"/cms/asset/a9d71771-3d01-469f-8b58-14688bdeae41/jgrb70323-math-0001.png\"&gt;&lt;/span&gt;&lt;mjx-container ctxtmenu_counter=\"177\" ctxtmenu_oldtabindex=\"1\" jax=\"CHTML\" role=\"application\" sre-explorer- style=\"font-size: 103%; position: relative;\" tabindex=\"0\"&gt;&lt;mjx-math aria-hidden=\"true\" location=\"graphic/jgrb70323-math-0001.png\"&gt;&lt;mjx-semantics&gt;&lt;mjx-mrow&gt;&lt;mjx-mo data-semantic-font=\"italic\" data-semantic- data-semantic-role=\"addition\" data-semantic-speech=\"italic plus or minus\" data-semantic-type=\"operator\"&gt;&lt;mjx-c&gt;&lt;/mjx-c&gt;&lt;/mjx-mo&gt;&lt;/mjx-mrow&gt;&lt;/mjx-semantics&gt;&lt;/mjx-math&gt;&lt;mjx-assistive-mml display=\"inline\" unselectable=\"on\"&gt;&lt;math altimg=\"urn:x-wiley:21699313:media:jgrb70323:jgrb70323-math-0001\" display=\"inline\" location=\"graphic/jgrb70323-math-0001.png\" xmlns=\"http://www.w3.org/1998/Math/MathML\"&gt;&lt;semantics&gt;&lt;mrow&gt;&lt;mo data-semantic-=\"\" data-semantic-font=\"italic\" data-semantic-role=\"addition\" data-semantic-speech=\"italic plus or minus\" data-semantic-type=\"operator\" mathvariant=\"italic\"&gt;±&lt;/mo&gt;&lt;/mrow&gt;$mathit{pm }$&lt;/annotation&gt;&lt;/semantics&gt;&lt;/math&gt;&lt;/mjx-assistive-mml&gt;&lt;/mjx-container&gt;0.2 magnitude units. Our appr","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"26 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147753419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Unified Micromechanical Model for Brittle Failure From Slow Creep to Dynamic Rupture","authors":"Lintong Jiang, Shihuai Zhang","doi":"10.1029/2025jb033680","DOIUrl":"https://doi.org/10.1029/2025jb033680","url":null,"abstract":"Brittle rock failure spans an exceptionally broad spectrum of strain rates, from slow creep to dynamic rupture, yet a unified physical model capturing this rate-dependent strength evolution remains elusive. Here we present a micromechanics-based model that integrates rate-and-state friction (RSF) on microcracks with inertial effect at crack tips to predict rock strength across this full spectrum. Uniaxial creep experiments on single closed cracks with varying orientations reveal decelerating slip at subcritical stresses, well described by RSF laws. Such time-dependent creeping slips can initiate wing cracks under sustained loading, motivating an extension of the classical wing crack model to incorporate RSF-controlled slip at low strain rates and inertial effect at high strain rates. The resulting micromechanical model identifies three rate-dependent strength regimes in rocks with pervasive microcracks: (a) a healing regime at low rates, where strength increases with decreasing rate due to frictional healing; (b) a frictional strengthening regime at intermediate rates, governed by rate-sensitive slip on microcracks; and (c) an inertia-dominated regime at high rates, where dynamic fracture resistance increases sharply. The model unifies classical Hoek-Brown and Mohr-Coulomb criteria within this micromechanical framework. It can be extended to incorporate environmental factors, including temperature, pore-pressure, and subcritical crack growth, which collectively govern the rate dependence of rock strength. These results offer new insights into rate- and stress-dependent crustal strength, helping to explain intraplate versus interplate earthquake recurrence patterns and pervasive rupture in the upper crust. It also improves the physical understanding and prediction of brittle rock failure across diverse geological settings.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"41 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147695883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Hybrid Probabilistic Framework for Mixed Discrete–Continuous Subsurface Parameter Estimation From Multi-Physics Geophysical Data: A Case Study for Quantifying the Geofluid Mapping in the Crust and Upper Mantle","authors":"Chunjie Zhang, Hikaru Iwamori","doi":"10.1029/2025jb032854","DOIUrl":"https://doi.org/10.1029/2025jb032854","url":null,"abstract":"Joint estimation of discrete (e.g., lithology or geofluid type) and continuous (e.g., porosity, pore geometry, related connectivity) subsurface parameters represents a challenging inverse problem due to strong parameter trade-offs, effective non-uniqueness, and multi-modal posterior structures. In many conventional deterministic or single-physics inversion approaches, discrete and continuous parameters are treated separately, and posterior uncertainty is often simplified, limiting the ability to evaluate competing model interpretations in a consistent probabilistic framework. Here we propose a generalized hybrid probabilistic inversion framework for mixed discrete–continuous parameter estimation using multi-physics observations. The framework integrates three key components: (a) grid-based marginal screening to down-select plausible discrete models over the joint parameter space; (b) targeted Monte Carlo refinement within the retained subspaces to reconstruct posterior distributions of continuous parameters for competing discrete models; (c) Discrete inference is conditioned on high-posterior-density regions of the continuous parameter space. Synthetic benchmark tests under noise-free demonstrate robust recovery of continuous parameters and lithology–geofluid combinations. Application to real seismic velocity and electrical conductivity data from the northeastern Japan Arc further shows that the proposed framework yields stable posterior estimates with transparent uncertainty quantification and well-resolved parameter trade-offs across different noise levels. By explicitly representing multi-modal posterior structures while maintaining computational efficiency, the proposed framework provides a practical and scalable solution for mixed discrete–continuous geophysical inverse problems, demonstrated here for lithology–geofluid inversion using seismic velocity and electrical conductivity data.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"5 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147753418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Testing Models for Upper Mantle Earthquakes in the Tanganyika-Rukwa Rift, Africa","authors":"Eduardo Arzabala, Cynthia Ebinger, Finnigan Illsley-Kemp, Aude Lavayssière, Derek Keir","doi":"10.1029/2025jb033104","DOIUrl":"https://doi.org/10.1029/2025jb033104","url":null,"abstract":"Rifts that initiate in mechanically strong, stable continental lithosphere are characterized by M &gt; 5 earthquakes at depths &gt;35 km near or below the crust mantle interface. Current models for deep rift zone earthquakes invoke elevated pore pressures associated with magmatism, and rapid stressing from magma intrusions. We evaluate the role of static stress changes caused by lateral density contrasts (magma intrusions) in the upper mantle and crust-mantle interface on mantle earthquakes. We use numerical models of static stress changes, and test models against seismic data from the Tanganyika rift, East Africa which has upper mantle earthquakes and locally elevated crustal Vp/Vs. The earthquake source mechanisms from these ML2.4–2.8 earthquakes show steep nodal planes and little correlation to crustal source mechanisms and E–W extension direction. Likewise, the direction of fast splitting from seismic anisotropy studies is oblique to predictions from earthquake source mechanisms. The models of density contrasts (magma intrusions) explored in this study predict differential stresses of 1–10 MPa, stresses consistent with average earthquake stress drops. The local stress field rotations around the edges of intrusive bodies can explain the variable source mechanisms and match the local rotation of shear wave splitting direction, providing a plausible mechanism for mantle earthquakes in cratonic rifts. By analogy, exhumed mantle from rift zones reveals pseudotachylites near intrusions. Metasomatic reactions in contact aureoles broaden density contrasts and reduce upper mantle strength, potentially enabling extension of initially cold, strong continental lithosphere.","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"5 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147753414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}