Journal of Geophysical Research: Solid Earth最新文献

{"title":"Monitoring Spatiotemporal Seismic Velocity Changes Using Seismic Interferometry and Distributed Acoustic Sensing in Mexico City","authors":"Yang Li,&nbsp;Mathieu Perton,&nbsp;Laura A. Ermert,&nbsp;Francisco J. Sánchez-Sesma,&nbsp;Leobardo I. Escobar Maya,&nbsp;Zack J. Spica","doi":"10.1029/2024JB030697","DOIUrl":"10.1029/2024JB030697","url":null,"abstract":"<p>Distributed Acoustic Sensing (DAS) offers a transformative solution for dense, high-resolution seismic monitoring to address the challenges of traditional seismometers in urban seismic surveys. Here, we employ seismic interferometry of the ambient noise field and the trace stretching method to monitor seismic velocity variations in Mexico City. We present spatiotemporal variations in relative Rayleigh wave group velocity <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>(</mo>\u0000 <mrow>\u0000 <mi>d</mi>\u0000 <mi>U</mi>\u0000 <mo>/</mo>\u0000 <mi>U</mi>\u0000 </mrow>\u0000 <mo>)</mo>\u0000 </mrow>\u0000 <annotation> $(dU/U)$</annotation>\u0000 </semantics></math> calculated over two frequency bands (0.4–1.2 Hz and 1.2–3.6 Hz) using DAS data collected over a year. To investigate these variations, we model the impacts resulting from the 2022 Mw7.6 earthquake, along with the effects of precipitation and temperature on the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>d</mi>\u0000 <mi>U</mi>\u0000 <mo>/</mo>\u0000 <mi>U</mi>\u0000 </mrow>\u0000 <annotation> $dU/U$</annotation>\u0000 </semantics></math> calculated in the 0.4–1.2 Hz frequency band, which is primarily dominated by the fundamental mode of the Rayleigh waves. Our results indicate that the earthquake-induced velocity drop differs in certain fiber sections, likely due to their non-linear soil behaviors and co-seismic stress changes but without relation to the maximum local deformation registered during the earthquake. Additionally, our modeling indicates that the velocity changes are influenced by seasonal temperature variations, and the impact of precipitation is relatively minor, at least for the depth range (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>&lt;</mo>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${&lt; } sim $</annotation>\u0000 </semantics></math>50 m) examined in this study. This study highlights the capability of DAS to enhance spatiotemporal monitoring in urban environments, providing valuable insights into both seismic and environmental responses.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB030697","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144888452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strain Energy Transfer by Plastic Flow in San-In Shear Zone, Japan: Shear Strain Energy Change Due To Out-Of-Plane Inelastic Strain Distribution","authors":"Tatsuhiko Saito,&nbsp;Angela Meneses-Gutierrez,&nbsp;Sachiko Tanaka,&nbsp;Tomotake Ueno","doi":"10.1029/2024JB030245","DOIUrl":"10.1029/2024JB030245","url":null,"abstract":"<p>The present study investigated the shear strain energy changes in a shear zone associated with distributed deep deformation and strike-slip earthquakes. A model of a very long strike-slip fault system was developed in which an inelastic strain distribution is introduced as deformation source. We derived analytical solutions for displacement and stress to estimate the changes in the shear strain energy. Applying this model to the San-in shear zone, Japan, we reproduced the observed surface velocity distribution. Our findings indicate that the deep shear deformation decreases the strain energy in deep crust and increases it in the shallow seismogenic zone, suggesting energy transfer. We also found that the deep shear deformation roughly follows a simple flow law, with the inelastic strain rate aligned with the background stress field, indicating plastic flow beneath the seismogenic zone. However, the width of the deep plastic flow remains poorly constrained by surface deformation observations. The coseismic energy drop at the centroid of the earthquake fault associated with two large earthquakes (Mw 7.0 and 6.6) was inferred to correspond to an energy accumulation period of approximately 500–2,000 years.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB030245","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144885100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupled Effects of Bedding Angle and Bedding Structure on the Anisotropic Mechanical and Failure Behaviors of Shales: Numerical Simulations on Digital Rocks","authors":"Dingdian Yan,&nbsp;Luanxiao Zhao,&nbsp;Minghui Lu,&nbsp;Yonghao Zhang,&nbsp;Zhanshan Xiao,&nbsp;Fengshou Zhang","doi":"10.1029/2025JB031436","DOIUrl":"10.1029/2025JB031436","url":null,"abstract":"<p>Bedding angle and structural characteristics are fundamental attributes of laminated shales, and their interplay inherently governs anisotropic mechanical behavior. A deep understanding of these governing mechanisms is crucial for advancing geo-engineering evaluations across various fields of Earth and Energy Sciences. However, shale's intrinsic heterogeneities complicate experimental research and hinder the unraveling of the underlying physical mechanisms. We integrated geological data into a discrete element model to construct anisotropic digital shales, enabling a combined analysis of the coupled effects of bedding angle and structures on mechanical responses under compressive loading. Results show that Young's modulus increases with bedding angle, while compressive strength displays a V-shaped trend, and Poisson's ratio shows the opposite pattern. Critical bedding angles for minimum strength and maximum Poisson's ratio vary across bedding structures-45<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $mathit{{}^{circ}}$</annotation>\u0000 </semantics></math> for finely laminated, 60<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $mathit{{}^{circ}}$</annotation>\u0000 </semantics></math> for laminated, and 30<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> $mathit{{}^{circ}}$</annotation>\u0000 </semantics></math> for massive shales. This finding may help explain the variability of critical angles observed in previous experiments. Strength and modulus anisotropy also differ among shale types: finely laminated shale has the lowest strength but highest modulus anisotropy, while massive shale exhibits the opposite trend. Micro-damage analysis shows that at small bedding angles, axial deformation dominates, while interlayer slip is limited. Increasing bedding angles induces stress concentration along bedding planes, enhancing shear slip and reducing axial strain, resulting in failure concentrated at bedding interfaces. Across varying bedding structures, bedding-plane shear slip reaches the maximum at its critical angle, promoting intensive crack development along bedding planes. Strength variation reflects the internal stress transmission heterogeneities governed by bedding features.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144885102","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":"Geomagnetic Reversals and Excursions as an Outcome of Non-Equilibrium Wave-Turbulence and Beating MAC Waves in the Core","authors":"Krzysztof A. Mizerski","doi":"10.1029/2024JB030679","DOIUrl":"10.1029/2024JB030679","url":null,"abstract":"<p>The turbulence in the liquid iron within the outer core of the Earth is responsible for the geomagnetic field generation, its sustainment and dynamical evolution. Here we revive Braginsky's idea of the Stratified Ocean at the top of the Core (SOC) and consider a non-stationary turbulent wave field composed of Magnetic-Archimedean-Coriolis (MAC) waves inside the SOC. The non-stationarity, hitherto ignored, implies non-vanishing coupling of waves with distinct frequencies, in particular the effect of beating waves leading to formation of electromotive force slowly varying in time in the core. It is shown that the beating frequencies, that is small frequency differences between interacting MAC waves can lead to an Earth-like behavior of the large-scale magnetic field, exhibiting long periods of fairly stable field separated by short lived reversals or strong excursions, which appear to be random. Within such an approach the resulting reversals/excursions are simply manifestations of a chaotic turbulent flow inside the core, and no significant alterations of the large-scale flow structures are necessary in order for reversals to occur. Such a dynamical picture seems highly desired since it has been a long-standing puzzle that many previous numerical simulations of the Earth's core dynamo exhibiting magnetic field reversals reported no significant modifications of large-scale flow structures during the process and only local variations in strength of the background small-scale turbulence.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB030679","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144885101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Olivine Water Contents in the Paleozoic Mengyin Kimberlites: Implications for the Destruction of the North China Craton","authors":"Yang Gao,&nbsp;Yong-Feng Wang,&nbsp;Da-Peng Wen,&nbsp;Hai-Jin Xu,&nbsp;Jun-Feng Zhang,&nbsp;Ke-Qing Zong","doi":"10.1029/2025JB032078","DOIUrl":"10.1029/2025JB032078","url":null,"abstract":"<p>The Mesozoic lithospheric thinning of the North China Craton (NCC) has been linked to water introduced from the subducted Paleo-Pacific oceanic slab. However, the pre-thinning hydration state of the NCC's lithospheric mantle is poorly constrained, leading to uncertainties regarding the impact of subduction-induced hydration. To address this gap, we investigated the petrography and mineral chemistry of olivine from the Paleozoic Mengyin kimberlites in the eastern NCC. These olivines are identified as xenocrysts derived from peridotite disaggregation rather than being primary crystallization products of the kimberlites. Fourier transform infrared spectroscopy analysis revealed that the water content in the olivine ranges from 13 to 281 ppmw, which may represent lower limits due to potential H diffusion loss. The enrichment in water represented by the higher end of this range is attributed to metasomatism by asthenosphere-derived melts. Our findings suggest that the relatively high water contents were a characteristic of the NCC lithospheric mantle since at least the Early Paleozoic. Furthermore, viscosity models show that even with olivine containing 100–600 ppmw water, the viscosity ratios between the cratonic root and the asthenosphere are substantially higher (&gt;300 to 1.4 × 10⁴), supporting a thick lithospheric keel (&gt;200 km) under the NCC during the Paleozoic. These results challenge the notion that olivine hydration is decisive for the stability or destruction of the NCC, suggesting instead that the contribution of water from the subducted Paleo-Pacific slab to the weakening of the NCC lithospheric mantle—and thus to its decratonization—is marginal.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144885099","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 Roles of Shear Displacement and Normal Stress on Earthquake Nucleation in Meter-Scale Laboratory Faults","authors":"David C. Bolton,&nbsp;Srisharan Shreedharan,&nbsp;Demian Saffer,&nbsp;Daniel T. Trugman","doi":"10.1029/2025JB031696","DOIUrl":"10.1029/2025JB031696","url":null,"abstract":"<p>Earthquake nucleation is a fundamental problem in earthquake science and has practical implications for forecasting seismic hazards. Laboratory experiments performed on large, meter-scale fault systems offer unique insights into the nucleation process because the migration and expansion of the nucleation zone can be precisely detected, measured, and characterized using arrays of local strain and slip measurements. We report on a series of laboratory experiments conducted on a 1-m direct shear machine. We sheared layers of quartz gouge between roughened acrylic forcing blocks over a range of normal stresses between 3 and 12 MPa, generating a spectrum of slip modes, ranging from aseismic creep to fast-dynamic rupture. Co-seismic slip, peak slip velocity, and high-frequency acoustic energy content of laboratory earthquakes increases systematically with both cumulative fault slip and normal stress. Slower and smaller laboratory earthquake sequences have larger nucleation zones, creep more during their inter-seismic period, and are deficient in high-frequency energy compared to larger and faster rupture sequences. We find that the critical nucleation length scale, <i>H*</i>, scales inversely with cumulative fault slip and normal stress. A reduction in <i>H*</i> and an increase in event size can be explained by a decrease in the critical slip distance, <i>D</i>_<i>c</i>, or an increase in the frictional rate parameter <i>b</i>–<i>a</i> and is likely driven by shear localization. Together, our results indicate that homogeneous, mature fault zones that have undergone more cumulative fault slip are expected to have smaller <i>H*</i> and can more easily host dynamic instabilities, relative to immature faults.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JB031696","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144869887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long Period Magnetotelluric Measurements in Southern South Island, New Zealand: The Resistivity Structure of Eastern Province Terranes","authors":"M. Ingham,&nbsp;K. Pratscher,&nbsp;W. Heise,&nbsp;E. Bertrand,&nbsp;M. Kruglyakov","doi":"10.1029/2024JB030346","DOIUrl":"10.1029/2024JB030346","url":null,"abstract":"<p>As part of a project to assess the risk posed by geomagnetically induced currents to the New Zealand electrical transmission network, long period magnetotelluric (MT) measurements have been made at 62 sites in southern South Island of New Zealand, a region where there was previously a complete absence of MT data. Analysis of the data using phase tensors and dimensionality indicators show that the data are largely 3-dimensional in character, but show distinct features which can be related to the known tectonic and geological structure. A 3-dimensional inversion of the data, using 2 independent codes, shows low resistivity to extend from the Moonlight Tectonic Zone, marking an spreading center which was active from 45 to 25 Myr, across the sandstones/siltstones of the adjacent Murihiku terrane. High resistivity is observed on the much older Fiordland Median Batholith and can also be traced along the length of the Dun Mountain Ophiolite Belt, a region of obducted oceanic crust which forms part of the Stokes Magnetic Anomaly. Variations in resistivity with depth agree well with features of the gravity field across the area as well as with seismic estimates of crustal thickness Resistivity contrasts across faults also mirror changes in seismic attenuation.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB030346","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144869719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Insights of the Conjugate Seismogenic Structure in the Northernmost Longitudinal Valley Revealed by the 2024 Hualien (Taiwan) Earthquake From Geodetic and Seismic Observations","authors":"Zhenjiang Liu,&nbsp;Jyr-Ching Hu,&nbsp;Zhenhong Li,&nbsp;Chen Yu,&nbsp;Chuang Song,&nbsp;Zhenyu Wang,&nbsp;Xuesong Zhang,&nbsp;Haihui Liu,&nbsp;Bingquan Han,&nbsp;Xiaoning Hu,&nbsp;Suju Li,&nbsp;Ming Liu,&nbsp;Jianbing Peng","doi":"10.1029/2024JB031025","DOIUrl":"10.1029/2024JB031025","url":null,"abstract":"<p>The Mw 7.4 Hualien earthquake, occurred in the northernmost Longitudinal Valley on 2 April 2024 is the strongest in Taiwan in 25 years. This study investigated fault geometry, slip distribution, and rupture process of the event, using teleseismic, regional strong-motion, and near-field geodetic observations as constraints, along with relocated aftershocks and their focal mechanisms for auxiliary validation and additional constraints. Furthermore, using the preferred rupture model determined in this study and 49 slip models of earthquakes between 1951 and 2022, collected or constructed from previous studies, we investigated the stress triggering of the 2024 Hualien event and reassessed the regional future seismic risk. Based on the joint inversion tests from different data set combinations under three candidate fault geometries, we preferred the model combining SEE-dipping and NWW-dipping faults as the causative structure. The coseismic rupture exhibits unilateral propagation along NNE direction, with significant slip occurring over approximately 30 km during the first 20 s. Combined with tectonic settings, background seismicity and joint finite-fault inversions, we further discussed the seismogenic structure, and inferred that the event may have conjugately ruptured the SEE-dipping deep Longitudinal Valley fault (LVF) and the NWW-dipping offshore backthrust fault. Based on Coulomb stress transfer, we found that preceding events first triggered the SEE-dipping fault, and its initial 6 s rupture subsequently activated the conjugate fault, which aligns with the rupture process we inverted. Additionally, we found that the event further exacerbated the seismic risk of the Ruisui-Shoufeng segment of the LVF.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144869722","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":"Toward Back-Projection Earthquake Rupture Imaging With Ocean Bottom Distributed Acoustic Sensing","authors":"Yuqing Xie,&nbsp;Jean-Paul Ampuero,&nbsp;Martijn van den Ende,&nbsp;Alister Trabattoni,&nbsp;Marie Baillet,&nbsp;Diane Rivet","doi":"10.1029/2025JB031483","DOIUrl":"10.1029/2025JB031483","url":null,"abstract":"<p>Distributed acoustic sensing (DAS) along seafloor fiber optic cables offers high-density, wide-aperture, real-time seismic data near subduction earthquakes, at a lower cost than conventional cabled ocean bottom seismic networks. It is thus a very promising approach to develop offshore observatories for hazard monitoring and mitigation and for fundamental research on earthquake processes. Here, we introduce a method for earthquake rupture imaging by back-projection of DAS data, taking full advantage of the data characteristics to achieve high resolution and accuracy. To develop and test the method, we use DAS data recorded along submarine telecom cables in Chile. The approach includes pre-processing steps, such as spatial integration and sediment time corrections, that greatly improve the back-projection performance. Our analysis of recordings of small earthquakes that can be considered as point sources demonstrates high accuracy in localizing seismic sources, with a resolution ranging from 2 to 5 km within a “high-resolution and high-robustness zone” around the cable. We demonstrate the ability of the method to image large ruptures by applying it to simulated waveforms of a magnitude seven earthquake, constructed by superposition of multiple empirical Green's functions. We find that strong coda waves do not compromise the precise detection and location of sub-sources. Our method could enhance early warning systems and offer high-resolution observations crucial for studying fault mechanics.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JB031483","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144869570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linking the Spin Transition of Ferric Iron in δ-(Al,Fe)OOH to Water Storage in the Lower Mantle","authors":"Johannes Buchen,&nbsp;Olivia S. Pardo,&nbsp;Vasilije V. Dobrosavljevic,&nbsp;Wolfgang Sturhahn,&nbsp;Takayuki Ishii,&nbsp;Stella Chariton,&nbsp;Eran Greenberg,&nbsp;Thomas S. Toellner,&nbsp;Jennifer M. Jackson","doi":"10.1029/2025JB031715","DOIUrl":"10.1029/2025JB031715","url":null,"abstract":"&lt;p&gt;As the most massive geochemical reservoir, the lower mantle affects the Earth's budget of volatile elements, including hydrogen or &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O. The properties of minerals in the lower mantle are further affected by changes in the electronic configurations of iron cations, that is, by spin transitions. The feedback between spin transitions and potential storage of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O in solid hydrous phases in the lower mantle, however, remains unexplored. By combining high-pressure nuclear resonant inelastic X-ray scattering and high-pressure high-temperature X-ray diffraction experiments, we constrained the thermal equation of state of δ-(Al,Fe)OOH, a member of the phase H solid solution. Based on the derived thermal equation of state of δ-(Al,Fe)OOH and the underlying thermodynamic model, we calculate the excess Gibbs free energy that arises from the spin transition of ferric iron in this compound and evaluate the effect on phase equilibria. The results of our analysis show that the spin transition of ferric iron in phase H may significantly reduce the thermodynamic activity and hence the concentration of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{H}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;O in a coexisting hydrous melt. As a consequence, nominally anhydrous minerals of the lower mantle may become dehydrated in the presence of phase H. Our analysis further suggests that, under certain conditions, the spin transition may expand the thermal stability of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mtext&gt;Fe&lt;/mtext&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;3&lt;/mn&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{Fe}}^{3+}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;-bearing phase H and create a geochemical link between the storage of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;H&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 8","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JB031715","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144870002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}