Physics of the Earth and Planetary Interiors最新文献

{"title":"Shear wave splitting characteristics of vertically aligned partial melt discs in a subduction zone back-arc setting","authors":"Eric Löberich , Jonathan Wolf , Maureen D. Long","doi":"10.1016/j.pepi.2025.107451","DOIUrl":"10.1016/j.pepi.2025.107451","url":null,"abstract":"<div><div>Could the strength of observed upper mantle anisotropy in regions of volcanic past be significantly influenced by partial melt inclusions? Patterns of SKS shear wave splitting (SWS), defined via fast polarization direction, <em>ϕ</em>, and delay time, <em>δt</em>, are commonly interpreted in terms of lattice-preferred orientation (LPO) of anisotropic minerals in the upper mantle. However, shape-preferred orientation (SPO) of elastically distinct materials may influence SWS observations as well. We carry out global wavefield simulations using AxiSEM3D to understand the effects of vertically aligned partial melt discs on shear waveforms and derived SWS observations. We confirm earlier findings that the amount of splitting depends, for example, on melt fraction and aspect ratio and demonstrate that the presence of melt SPO (MPO) can significantly increase <em>δt</em>. We explore to what extent a combination with E-type olivine fabric can explain the occurrence of exceptionally high <em>δt</em> in the southern Cascadia Subduction Zone (SCSZ) back-arc and evaluate the effect of dehydration-related fabric transition to A-type on SWS. In this modeling, we assume that the presence of vertical melt disc inclusions is related to continuous upwelling and decompression melting that led to the formation of dykes in the uppermost mantle. For each model we examine the spatial variation and statistical distribution of splitting parameters. For a model considering multiple melt regions, we further evaluate their directional dependence. Stations above the melt inclusions tend to a unimodal <em>δt</em> distribution and explain the high <em>δt</em> values and the wide range of <em>δt</em> observed in the SCSZ back-arc.</div></div><div><h3>Plain language summary</h3><div>Could mantle deformation caused by volcanic activity be detected by the directional dependence of seismic wave propagation referred to as seismic anisotropy? Shear waves that pass through an anisotropic medium split into two waves with different orientations of wave vibration. These two waves travel at different speeds and accumulate a time delay <em>δt</em>, which can be measured from a seismogram along with the orientation of the faster wave, <em>ϕ</em>. These parameters represent the strength and orientation, respectively, of anisotropy beneath a seismometer. Seismic anisotropy in Earth's upper mantle is often interpreted to be due to the deformation linked alignment of individual grains of olivine, the most common mineral to occur in this depth region. However, the alignment of pockets of partial melt in the upper mantle may also contribute to the observed anisotropy. In this study, we evaluate the potential of vertically aligned partial melt discs to explain unusual previous observations of <em>δt</em> in the southern Cascadia subduction zone, which include exceptionally high delay times with significant variability over small length scales. We computationally simulate the propagation ","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107451"},"PeriodicalIF":1.9,"publicationDate":"2025-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145120912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Data-driven crustal deformation model in southeastern Tibetan Plateau using unsupervised machine learning techniques for GNSS observations","authors":"Zhengyang Pan ,&nbsp;Yao Jin ,&nbsp;Meixuan Hao ,&nbsp;YangYang Diao","doi":"10.1016/j.pepi.2025.107440","DOIUrl":"10.1016/j.pepi.2025.107440","url":null,"abstract":"<div><div>The Southeastern Tibetan Plateau (STP) is a crucial place in understanding how stress is transmitted between the India-Eurasia collision belt and the surrounding blocks. It was accustomed to applying block models to study its deformation characteristics, which can hide or ignore some information due to the artificial division of the blocks. Therefore, we use an unsupervised machine learning method to analyze the tectonic deformation of the southeastern Tibetan Plateau without any prior information constraints. Firstly, we conducted K-means clustering analysis on GNSS velocity and identified the best cluster model using gap analysis, and we used Hierarchical Agglomerative Clustering to assess the reliability of this optimal cluster. Next, we used the method of spherical strain to obtain the translation rate, rotation rate, principal strain, surface strain, and second strain invariants for each cluster. After conducting cluster analysis and strain estimation, our results indicate that the oblique convergence of the Indian plate at the eastern Himalaya tectonic syntaxis is significantly involved in the deformation of the southeastern Tibetan Plateau. On the one hand, it slows down the crustal material migration caused by the gravitational potential energy in the Tibetan Plateau, resulting in the decrease of the rotation rate from the plateau to the middle of the STP. On the other hand, it encourages the lateral expansion of the STP, increasing the rotation rate from the central part of the STP to the Nantinghe fault and Menglian fault. This model has also confirmed the eastward growth mechanism of the Tibetan Plateau. It suggests that the oblique convergence of the Indian plate along the Eastern Himalayan tectonic syntaxis may be essential for the formation of regional tectonic deformation that has been ongoing since 20 million years ago.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107440"},"PeriodicalIF":1.9,"publicationDate":"2025-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145049618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Remarkable variations in geomagnetic disturbances preceding the 2017 M 7.1 Jiuzhaigou earthquake","authors":"Yiliang Guan ,&nbsp;Xiaona Dong ,&nbsp;Lili Feng ,&nbsp;Manqiu He ,&nbsp;Yingfeng Ji","doi":"10.1016/j.pepi.2025.107438","DOIUrl":"10.1016/j.pepi.2025.107438","url":null,"abstract":"<div><div>With the rapid development of geomagnetic observation networks and the increased availability of geomagnetic data in China over the past decade, multistation geomagnetic data analyses have become widely used in studies of earthquake precursors with magnitudes &gt;6. Building on the single-station polarization algorithm, we propose a multistation daily sliding polarization correlation algorithm for detecting regional geomagnetic anomalies. This method can be applied to analyze the spatiotemporal evolution of geomagnetic field anomalies that are related to seismogenic processes before major earthquakes. In this study, we calculate polarization correlation time series data before and after the 2017 M 7.1 Jiuzhaigou earthquake. The results show that following the appearance of polarization anomalies, the regional correlations increase, then decrease, and subsequently increase again. Earthquakes occurred at the inflection points of these correlation trends. Our analysis suggests that changes in multistation polarization correlations directly reflect regional geomagnetic field anomalies that are caused by tectonic activity, thereby capturing the dynamic evolution during earthquake preparation. This method offers valuable insights into the mechanisms linking geomagnetic polarization anomalies with seismic events.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107438"},"PeriodicalIF":1.9,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145049616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Local flow estimation at the top of the Earth’s core using Physics Informed Neural Networks","authors":"Naomi Shakespeare-Rees ,&nbsp;Philip W. Livermore ,&nbsp;Christopher J. Davies ,&nbsp;Hannah F. Rogers ,&nbsp;William J. Brown ,&nbsp;Ciarán D. Beggan ,&nbsp;Christopher C. Finlay","doi":"10.1016/j.pepi.2025.107424","DOIUrl":"10.1016/j.pepi.2025.107424","url":null,"abstract":"<div><div>The Earth’s main geomagnetic field arises from the constant motion of the fluid outer core. By assuming that the field changes are advection-dominated, and that diffusion only plays a minor role, the fluid motion at the core surface can be related to the secular variation of the geomagnetic field, providing an observational approach to understanding the motions in the deep Earth. The majority of existing core flow models are global, showing features such as an eccentric planetary gyre, with some evidence of rapid regional changes. By construction, the flow defined at any location by such a model depends on all magnetic field variations across the entire core–mantle boundary: because of this nonlocal dependence of the flow on the magnetic field, it is very challenging to interpret local structures in the flow as due to specific local changes in magnetic field. Here we present an alternative strategy in which we construct regional flow models that rely only on local secular changes. We use a novel technique based on machine learning termed Physics-Informed Neural Networks (PINNs), in which we seek a regional flow model that simultaneously fits both the local magnetic field variation and dynamical conditions assumed satisfied by the flow. Although we present results using the Tangentially Geostrophic flow constraint, we set out a modelling framework for which the physics constraint can be easily changed by altering a single line of code. After validating the PINN-based method on synthetic flows, we apply our method to the CHAOS-8.1 geomagnetic field model, itself based on data from Swarm. Constructing a global mosaic of regional flows, we reproduce the planetary gyre, providing independent evidence that the strong secular changes at high latitude and in equatorial regions are part of the same global feature. Our models also corroborate regional changes in core flows over the last decade. In our models, we find that the azimuthal flow under South America has changed sign quasi-periodically, with a recent sign change in 2022. Furthermore, our models endorse the existence of a dynamic high latitude jet, which began accelerating around 2005 but has been weakening since 2017.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"367 ","pages":"Article 107424"},"PeriodicalIF":1.9,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144932544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unraveling the lithospheric magnetic field masked by the Earth’s main field by estimating the magnetization and magnetic crustal thickness using a statistical approach","authors":"Erwan Thébault ,&nbsp;Gauthier Hulot","doi":"10.1016/j.pepi.2025.107421","DOIUrl":"10.1016/j.pepi.2025.107421","url":null,"abstract":"<div><div>Detailed mapping of Earth’s lithospheric magnetic field provides important insights into the composition, dynamics, and geological history of the crust. This field can be modeled using satellite and near-surface magnetic measurements. However, structures larger than approximately 2500 km in scale are obscured by the dominant magnetic signal generated by the Earth’s core. The superposition of core and crustal magnetic fields introduces ambiguities in both geodynamo and crustal magnetic source studies. Previous efforts to address this issue have included statistical estimates of upper and lower bounds on the long-wavelength components of the crustal field, as well as more deterministic predictions based on geophysical priors such as crustal magnetization and seismic Moho depth models. These approaches, however, have often produced contradictory results. In this study, we adopt a two-step strategy. The first step involves a series of regional spherical spectral analysis of the World Digital Magnetic Anomaly Grid (WDMAM2.2), without relying on any prior information from seismic or magnetization models. This approach, applied to the 5 km × 5 km WDMAM2.2 grid across 6000 regions uniformly distributed over the Earth’s surface, allows us to estimate the probability distributions of three key parameters statistically characterizing crustal magnetization in each of the 6000 regions: magnetization amplitude, magnetic layer thickness, and a power-law exponent. The resulting world map of magnetic layer thickness differs from existing Moho depth models but indicates that, statistically, there is no significant evidence of magnetic sources located below the Moho at the studied length scales. In the second step, the ensemble of regional magnetization models is used to generate a set of large-scale spherical harmonic models of the lithospheric magnetic field (degrees 1 to 50). This set allows us to quantify the extent to which the lithospheric field contaminates both the static and time-varying components of the core magnetic field. We find that this contamination is substantial between spherical harmonic degrees 12 and 15 for the static core field, and from degree 21 onward for the secular variation.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"367 ","pages":"Article 107421"},"PeriodicalIF":1.9,"publicationDate":"2025-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144896060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detecting low-latitude outer core-surface waves with 25 years of satellite secular variation data","authors":"Carla R. Grüne ,&nbsp;Kathryn A. Whaler ,&nbsp;Frederik Dahl Madsen","doi":"10.1016/j.pepi.2025.107435","DOIUrl":"10.1016/j.pepi.2025.107435","url":null,"abstract":"<div><div>Fluid motion in the Earth’s liquid outer core generates most of the geomagnetic field, and its time changes over timescales of one year or longer, the secular variation (SV). Data from the satellite missions Ørsted, CHAMP, CryoSat-2 and Swarm, together with data from ground observatories, were combined to yield a SV dataset spanning from late 1997 to early 2023. These SV data were inverted for time-varying core surface fluid velocity assuming it is purely advective, with the main field specified by the CHAOS-7.16 field model. The inversion was regularised both in time and in space. In time, the difference in velocity between individual epochs was minimised. In space, small-scale velocity structures were penalised. Flow acceleration was then calculated from first differences of velocities at successive epochs. Time-longitude diagrams of azimuthal acceleration show sloping features at low latitudes, interpreted as signatures of propagating waves. Waves propagating both eastwards and westwards were observed, with propagation velocities of approximately 1700 km/yr which is in agreement with previous inferences of fast core waves. Power spectral density plots reveal that the energy is concentrated in modes with periods of 6–7 years, and azimuthal wavenumbers −5, −2 and 2, where negative wave numbers indicate westward motion. There is a higher energy content in the westward propagating waves than in those travelling eastwards. Finally, we find intermittent low-latitude standing waves, which coincide with times of recent equatorial geomagnetic jerks, consistent with inferences of magneto-Coriolis and Alfvén waves from other studies.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"367 ","pages":"Article 107435"},"PeriodicalIF":1.9,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144906963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Seismic reflectors in the mid-lower mantle beneath central Pacific: The relationship with the Pacific LLSVP","authors":"Satoshi Kaneshima","doi":"10.1016/j.pepi.2025.107437","DOIUrl":"10.1016/j.pepi.2025.107437","url":null,"abstract":"<div><div>Seismic signals in P coda originating from deep mantle heterogeneity have not yet been investigated extensively, except for the observations of the waves reflected presumably at the top of the D″ layer. We show in this study that array processing of seismograms of deep earthquakes at Tonga-Fiji and Solomon Islands recorded by seismograph networks at southern California reveals strong off-great circle arrivals in P coda 5 to 10 s after direct P waves. We also show that the large arrivals observed for the Tonga-Fiji events are P-to-P reflected waves at a dipping interface in the mid-lower mantle beneath central Pacific. The reflector is located south-southeast of Hawaii around 2000 km depth and dips down to southeast by nearly 35°. The observed amplitude and polarity of the reflected waves could be explained if the Vp of the underlying side of the reflector is 1 to 2 % faster than the overlying side. The small Vp anomaly may not necessarily contradict the absence of a noticeable Vp anomaly in previous seismic tomography models at the site of the reflector. We also find that the reflected wave is approximately concomitant with a weaker arrival from a mid-mantle scattering object located nearly 1000 km closer to the hypocenters. The heterogeneous object causing the anomalous arrivals for the Solomon Islands events, although the properties of the object are less well constrained than the Tonga-Fiji reflector, also likely represents another dipping reflector at 2400 km located approximately below the Hawaiian hotspot. As in the Tonga-Fiji case the signals are occasionally followed by a weaker signal from a mid-mantle scattering object located nearer to the hypocenters. The mid-mantle reflection/scattering objects do not indicate the presence of a global discontinuity but must represent localized strong heterogeneities. It is notable that the localized heterogeneities are all located near the edges of a large low Vs body (the Pacific LLSVP) resolved by global tomography, up to 500 km above the LLSVP itself. The relation between the locations of the reflector/scatterers and the large scale Vp structure is unclear, probably reflecting poorer tomography images of Vp structure associated with the LLSVP. We discuss possible tectonic implications of these mid-mantle heterogeneities on the structure and evolution of the LLSVP.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107437"},"PeriodicalIF":1.9,"publicationDate":"2025-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144997579","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Complex deformation mechanisms of the Qinling orogenic belt lithosphere and clockwise rotation of the Yangtze craton crust: Insights from Rayleigh wave azimuthally anisotropic tomography","authors":"Tengfei Wu ,&nbsp;Shuangxi Zhang ,&nbsp;Meng Chen","doi":"10.1016/j.pepi.2025.107436","DOIUrl":"10.1016/j.pepi.2025.107436","url":null,"abstract":"<div><div>The collision and convergence between the Yangtze Craton (YZC) and North China Craton (NCC) beneath the Qinling orogenic belt (QOB) have resulted in complex lithospheric deformation, the mechanisms of which remain unclear. In this study, we extracted 10–60 s Rayleigh-wave dispersion curves using the two-station method from vertical-component waveform data of 1087 teleseismic events, recorded at 110 seismic stations across the QOB and adjacent regions. Subsequently, anisotropic tomography was employed to reconstruct high-resolution isotropic and anisotropic phase velocity models of the crust and upper mantle beneath the QOB and surrounding regions. We focused on analyzing deformation patterns in four key subregions of the QOB. Our results demonstrated that crustal deformation is affected by multiple geological factors. Major tectonic activities, such as island arc collisions, oceanic basin closure, and orogenic events, have fundamentally shaped the regional structural framework. Building on this, crustal lithological features, thrust tectonic movements, and the strike of fault systems, which together control present-day deformation. Furthermore, our anisotropic model, in combination with previous geodetic and seismological observations, suggests that the clockwise rotation of the YZC during its convergence with the NCC plays a significant role in influencing crustal deformation. Upper mantle deformation is primarily driven by absolute plate motion, with additional influences from the northeastward escape of material in the Tibetan Plateau and mantle flow. Notably, our anisotropic model provides new seismological evidence supporting the clockwise rotation of the YZC crust, which is closely related to the tectonic development of the Sichuan basin and the formation of the Dabashan arcuate structure. Integrating with previous studies, we propose a conceptual model to explain the formation mechanism of the Dabashan arcuate structure, which we attribute to the combined effects of the clockwise rotation of the YZC crust during the Middle to Late Triassic and the ongoing convergence between the YZC and the NCC. These findings provide new insights into the lithospheric dynamic processes of the QOB.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"367 ","pages":"Article 107436"},"PeriodicalIF":1.9,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantitative assessment of tomographic proxies for lowermost mantle composition and mineralogy","authors":"Justin Leung ,&nbsp;Andrew M. Walker ,&nbsp;Paula Koelemeijer ,&nbsp;Federica Restelli ,&nbsp;D. Rhodri Davies","doi":"10.1016/j.pepi.2025.107423","DOIUrl":"10.1016/j.pepi.2025.107423","url":null,"abstract":"<div><div>Large low velocity provinces (LLVPs) dominate Earth’s lowermost mantle, but their detailed thermochemical nature remains a topic of discussion. In particular, it is unclear to what extent the bridgmanite to post-perovskite phase transition is able to explain their seismic velocity characteristics. Robust constraints on the origin of these seismic structures would shed light on large-scale mantle dynamics and Earth’s thermal and chemical evolution. Here, we examine the combined effects of temperature, chemical heterogeneity and phase transitions on lowermost mantle tomographic signatures. To investigate this, we calculate synthetic seismic velocities expected from a range of scenarios for the stability of post-perovskite combined with models of different lowermost mantle temperatures and compositions using recent thermodynamic data. These are filtered to account for limited tomographic resolution, allowing for quantitative comparisons between our synthetic seismic velocities and a recent Backus-Gilbert based tomography model. Crucially, this model provides robust ratios and correlations of velocity anomalies derived from nearly identical <span><math><msub><mrow><mi>V</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>V</mi></mrow><mrow><mi>s</mi></mrow></msub></math></span> resolution, and includes uncertainty quantification that accounts for both data and theoretical errors. Given the tomographic uncertainties and limited resolution, our comparisons focus on globally and depth averaged seismic characteristics, which capture the effects of lateral compositional and mineralogical variability. By rejecting synthetic models that do not fit within tomographic uncertainties, we quantitatively eliminate the following: (i) models containing LLVPs with an iron-rich primordial composition, as these generate anomalously high root mean square seismic velocity anomalies; and (ii) models without post-perovskite in the lowermost mantle, as these cannot explain observations of elevated ratios of shear-wave to compressional-wave velocity (<span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>s</mi><mo>/</mo><mi>p</mi></mrow></msub></math></span>) and a negative correlation between variations in shear-wave and bulk sound velocity (<span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>s</mi><mo>−</mo><mi>c</mi></mrow></msub></math></span>). Additionally, we demonstrate that observations of <span><math><msub><mrow><mi>R</mi></mrow><mrow><mi>s</mi><mo>/</mo><mi>p</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>s</mi><mo>−</mo><mi>c</mi></mrow></msub></math></span> in the lowermost mantle cannot be explained by thermochemical LLVPs alone, but require bridgmanite and post-perovskite to co-occur at depth in the mantle. As such, we demonstrate that globally averaged seismic velocity characteristics can distinguish between composition and mineralogy in the lowermost mantle.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107423"},"PeriodicalIF":1.9,"publicationDate":"2025-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145011038","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crustal anisotropy as evidence for hydration of the Martian upper mantle","authors":"William D. Frazer ,&nbsp;Jeffrey Park ,&nbsp;Frederik Link","doi":"10.1016/j.pepi.2025.107434","DOIUrl":"10.1016/j.pepi.2025.107434","url":null,"abstract":"<div><div>Constraining the structure of the Martian lithosphere below the InSight lander is essential to our understanding of Elysium Planitia and the evolution of the whole planet. Previously, seismic imaging using data recorded by the SEIS instrument suggested three crustal interfaces at ∼8, ∼20, and ∼ 43 km depth. Additionally, a shallower small interface at ∼2 km has been identified. We estimate multiple-taper correlation receiver functions from records for 34 seismic events on Mars. We extend the bandwidth of frequencies considered and offer the finest vertical resolution yet. We conduct shear-wave splitting analysis and stochastic inversion of P-to-s converted phases to estimate anisotropic parameters of the major crustal layers. Our analysis identifies anisotropy (12–14 %) in the lower layers of the Martian crust. We suggest that the deepest layer of the Martian crust beneath InSight formed during modification of the upper mantle during volcanism, not differentiation generated by Borealis impactor. Our proposed underplating process could have been metasomatic and involved hydration from an early ocean on Mars.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"367 ","pages":"Article 107434"},"PeriodicalIF":1.9,"publicationDate":"2025-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}