Journal of Geophysical Research: Solid Earth最新文献

{"title":"Magnetotelluric Adaptive Inversion Using Multi-Resolution Tetrahedral Grids: Application to the North China Craton","authors":"Huang Chen,&nbsp;Zhengyong Ren,&nbsp;Jingtian Tang","doi":"10.1029/2024JB030405","DOIUrl":"https://doi.org/10.1029/2024JB030405","url":null,"abstract":"<p>We developed a novel three-dimensional magnetotelluric adaptive inversion algorithm optimized to interpret field datasets collected in realistic geological environments. Using a newly designed data-driven indicator, it tends to enhance features in data-sensitive regions and generate a set of multiscale inversion models with gradually increased resolution. Additionally, utilizing the nested tetrahedral grids, it meets different mesh resolution requirements for forward modeling and inversion, which addresses the trade-off between modeling accuracy and computational load. Validation against synthetic data confirms the algorithm's ability to efficiently delineate subsurface structures, notably enhancing the interpretability of magnetotelluric data. We applied the proposed algorithm to reinterpret field magnetotelluric data collected in the North China Craton within complex geological settings. The resulting conductivity structures reveal consistent high conductivity anomalies in the western Ordos Basin and the North China Plain, reflecting younger geological conditions. Additionally, high resistivity characteristics are observed beneath mountains such as the Luliang and Taihang Mountains, and three common high-conductivity anomalies from the upper mantle are identified. Notably, we found a previously identified conductor at 20–70 km depth beneath the southern Bohai Bay Basin, previously interpreted as electrical conductivity anisotropy, is now positioned at a deeper depth near the lithosphere-asthenosphere boundary, suggesting it may represent upwelling asthenospheric material. This research highlights the proposed adaptive inversion algorithm's potential to enhance subsurface imaging in geophysical exploration, with future integrations with other geophysical methods and efficiency improvements poised to extend its applicability to more complex datasets, aiding resource exploration, geohazard assessment, and deep Earth studies.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143824641","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":"Inferring 3-D Rheology of Low-Viscosity Zone Around Quaternary Volcanoes of NE Japan From Postseismic Deformation of the 2011 Tohoku-Oki Earthquake","authors":"Sambuddha Dhar,&nbsp;Youichiro Takada,&nbsp;Jun Muto","doi":"10.1029/2024JB029939","DOIUrl":"https://doi.org/10.1029/2024JB029939","url":null,"abstract":"<p>Several geological and geophysical studies suggest the small-scale presence of low viscosity zone (i.e., LVZ) beneath the Quaternary volcanoes of northeastern Japan. Before the 2011 <i>M</i>_<i>w</i>9.0 Tohoku-oki earthquake, scientists hypothesized that these LVZs cause localized crustal deformations around the Quaternary volcanoes. However, the deformation-signals related to these LVZs were too weak to properly understand the LVZ rheology. After the 2011 Tohoku-oki earthquake, InSAR and Global Navigation Satellite System (GNSS) observations reported significant ground movements around five Quaternary volcanoes including the Mt. Akitakoma, Mt. Kurikoma, Mt. Zao, Mt. Azuma, and Mt. Nasu. Using the early years of postseismic GNSS displacements, we extracted the short-wavelength components of strain-rate distribution, which clearly show the localized crustal contraction near the five volcanoes. To explain such spatial pattern of localized contraction, we propose a 3-D rheological model of LVZs near the five volcanoes, using power-law Burgers rheology. Most of our modeled LVZs have narrow tops (width of 20–40 km), wide roots (width of 80–100 km), limited arc-parallel dimensions (≤80 km), and are located at the depth range of 15–55 km in the lower crust-upper mantle. Based on the localization of postseismic strain rate, newly proposed 3-D LVZ models highlight an arc-parallel heterogeneity of subsurface rheology along the volcanic front of northeastern Japan, which is consistent with previously reported clusterization pattern of late Cenozoic calderas and high geothermal gradient near the five Quaternary volcanoes.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029939","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143824642","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":"Mapping the Crustal Magmatic System and Regional Deformation of the Toba Region by Multiparameter Ambient Noise Adjoint Tomography","authors":"Kai Wang,&nbsp;Ping Tong,&nbsp;Zhengjie Zhang,&nbsp;Lurun Su","doi":"10.1029/2024JB030550","DOIUrl":"https://doi.org/10.1029/2024JB030550","url":null,"abstract":"&lt;p&gt;In this study, we develop a multiparameter ambient noise adjoint tomography method, and apply it for the first time to image the crustal magmatic system and regional deformation of the Toba region. Using Rayleigh and Love waves at periods of 5–20 s extracted from ambient noise, we construct a new multiparameter 3D crustal model that includes shear-wave velocity, radial and azimuthal anisotropy. The isotropic component of our model reveals (a) over 30% Vs reductions beneath the Toba caldera with a melt fraction ranging from &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;14.5&lt;/mn&gt;\u0000 &lt;mi&gt;%&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $14.5%$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; to &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;18.5&lt;/mn&gt;\u0000 &lt;mi&gt;%&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $18.5%$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and (b) two low Vs bodies located in the middle crust (10–20 km) beneath the Helatoba volcano and the upper crust beneath the Lubukraya volcano, suggesting a large transcrustal magmatic mush model beneath this volcanic arc region. Our anisotropic model shows &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;&gt;&lt;/mo&gt;\u0000 &lt;mn&gt;10&lt;/mn&gt;\u0000 &lt;mi&gt;%&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${ &gt;} 10%$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; positive radial anisotropy &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mi&gt;h&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;&gt;&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;V&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;s&lt;/mi&gt;\u0000 &lt;mi&gt;v&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left({V}_{sh} &gt; {V}_{sv}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; in the middle crust of the volcanic regions, indicating the presence of horizontally layered melt sills. In the upper crust, we find predominantly weak negative radial anisotropy and significant azimuthal anisotropy, suggesting subvertical rock fabrics dominate upper crustal anisotropy. The orientation of fast velocity directions (FVDs) mostly aligns with the Sumatran Fault due to fault fabrics resulting from shearing deformation along the plate boundary. In the Tarutung region with rich geothermal resources, FVDs shift to being fault-perpendicular probably due to the alignment of stress-","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822210","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":"Softening and Recovery of Near-Surface Layers During the 2024 M7.6 Noto Earthquake","authors":"Miroslav Hallo,&nbsp;Kimiyuki Asano,&nbsp;Tomotaka Iwata","doi":"10.1029/2024JB029961","DOIUrl":"https://doi.org/10.1029/2024JB029961","url":null,"abstract":"<p>On 1 January 2024, a devastating <i>M</i>_<i>J</i> 7.6 earthquake occurred on the Noto Peninsula in Japan. When such a strong earthquake occurs, affected near-surface soil layers behave nonlinearly and may undergo some structural changes driven by Flow Liquefaction, Cyclic Mobility, or Slow Dynamics phenomena. The structural changes can be manifested by short-lasting coseismic and long-lasting postseismic site-response changes that are related to variations in near-surface shear-wave velocity. To examine this behavior, we perform a systematic analysis of Horizontal-to-Vertical (H/V) spectral ratios from regional earthquake waveforms recorded at 160 sites in the years 1996–2024. We identify significant H/V peaks and their directionality in the frequency range of 0.1–25 Hz separately for periods before and after the <i>M</i>_<i>J</i> 7.6 earthquake. This allows us to measure long-lasting relative changes in predominant frequency caused by the strong shaking, with maximum drops of −21% and a dependence on experienced ground motion levels. Next, the short-lasting changes during the <i>M</i>_<i>J</i> 7.6 earthquake reveal strongly nonstationary behavior. The frequency of spectral peaks decreases simultaneously and omnidirectionally with the strong shaking and then logarithmically recovers. The observed extreme short-lasting predominant frequency drops reach −93% relative to the initial value, and their occurrence time divides the nonstationary behavior into elastic softening and recovery phases. This behavior is physically related to temporal changes in near-surface shear-wave velocity as a consequence of changes in shear moduli. The introduced phenomenon of elastic softening and recovery may have a significant impact on a broad scale of geophysical research topics.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143824640","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":"Modelling Partial Melting in Sinking Greenstone Belts With Implications for Archaean Continental Crust Formation","authors":"Guangyu Huang,&nbsp;Ross N. Mitchell,&nbsp;Richard M. Palin,&nbsp;Mingguo Zhai,&nbsp;Richard W. White,&nbsp;Christopher J. Spencer,&nbsp;Jinghui Guo","doi":"10.1029/2024JB030204","DOIUrl":"https://doi.org/10.1029/2024JB030204","url":null,"abstract":"<p>Tonalite–trondhjemite–granodiorite (TTG) gneisses are the dominant component of Archaean continental crust, with their parent magmas generally thought to have formed due to the partial melting of hydrated basalts; however, this process typically produces melts with a notably lower Mg^# than most natural TTGs. By contrast, ultramafic volcanic rocks commonly preserved in Archaean greenstone belts may represent an alternative source of TTG magma that has been largely overlooked. Here, we use petrological modelling to investigate anatexis of komatiites and komatiitic basalts from the Warrawoona Group of the Pilbara craton. In all cases, komatiite is refractory and generates no melt within the pressure-temperature range considered. Komatiitic basalts, however, could produce 20–25 vol. % of MgO-rich melts during greenstone belt sinking and hot subduction. Anatexis of komatiitic basalts generates melt fractions too depleted in large ion lithophile elements to represent natural TTGs; however, hybridization of melts produced by partial melting of tholeiitic basalts and komatiitic basalts during crustal overturn would generate magma that resembles natural TTGs. All calculated melts are felsic in composition, and TTGs with high Mg^# could have been generated entirely within the crust, with no requirement for the assimilation of mantle materials. By contrast, Archaean sanukitoids require some assimilation of mantle materials with crustal melts, indicating that the oldest sanukitoids preserved in each Archaean craton may record temporary and localized subduction on the early earth. The ubiquitous occurrence of sanukitoids worldwide by <i>c</i>. 2.7 Ga may provide a minimum age for the onset of global plate tectonics.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818586","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":"Earth's Deep-Time Geodynamic Evolution Recorded by Hafnium Isotope Perturbations","authors":"Zhen-Jie Zhang,&nbsp;Timothy Kusky,&nbsp;Guo-Xiong Chen,&nbsp;Qiu-Ming Cheng","doi":"10.1029/2025JB031150","DOIUrl":"https://doi.org/10.1029/2025JB031150","url":null,"abstract":"<p>Interactions between Earth's mantle and crust have shaped the planet's evolution through deep time. Hafnium (Hf) isotopes provide a unique fingerprint of magma sources, enabling the tracking of the crucial interaction zone in the upper mantle evolution through more than four billion years of Earth's history. However, previous studies have relied on a combination of evolved and juvenile zircons, making it challenging to distinguish the genuine evolution of mantle properties. Here, we present a global compilation of Hf isotopic analyses of zircons from juvenile crust to track the upper mantle's evolution throughout Earth's history. By employing Singular Spectrum Analysis and Wavelet Analysis for time series, we decompose the complex Hf isotopic evolution curves and determine the respective periods and interpretations of each component. Our analysis reveals a complex and dynamic evolution of the upper mantle, with distinct periods of stability and upheaval. We show that the upper mantle has undergone periodic perturbations through mixing with crustal materials since Earth's formation, primarily caused by plate subduction and weakly influenced by mantle convective cycles. Hf isotopes reveal vigorous mantle convection that propelled plate tectonics during the Hadean, along with numerous supercontinent cycles that originated in the early Mesoarchean and a notable shift in subduction modes during the Neoproterozoic. This Hf isotope survey provides new insights into Earth's tectonic machinery, advancing our understanding of the planet's geological history.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818729","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":"Investigation of Submarine Permafrost Conditions in the Canadian Beaufort Sea Using Diving Wave Tomography","authors":"H. Grob,&nbsp;D. Klaeschen,&nbsp;M. Riedel,&nbsp;S. Krastel,&nbsp;M. J. Duchesne,&nbsp;J. Bustamante,&nbsp;G. Fabien-Ouellet,&nbsp;Y. K. Jin,&nbsp;J. K. Hong","doi":"10.1029/2024JB029955","DOIUrl":"https://doi.org/10.1029/2024JB029955","url":null,"abstract":"<p>Submarine permafrost in the Canadian Beaufort Sea is relict terrestrial permafrost, which is continuously degrading since the change of thermal conditions induced by a marine transgression that followed the last glaciation. Permafrost degradation has a crucial socio-ecological significance because its thawing can result in geohazards like landslides or an increase in greenhouse gas emissions. These consequences are mostly regulated by the state of ice in permafrost. In this study, we use marine multichannel seismic data to apply a diving wave tomographic inversion on the outer 50 km of the Canadian Beaufort Shelf. Due to the close relationship between seismic velocity and ice content, we are able to infer detailed information about the present submarine permafrost condition. We find a clear variability of permafrost occurrences between the inner and outer Canadian Beaufort Shelf. At the inner shelf, discontinuous ice-bonding permafrost occurs extensively close to the seafloor but is interrupted by taliks. Within the outer ∼27 km of the shelf, ice-bonding permafrost is absent in the upper sediments and its top has plunged to &gt;200 m below sea level. These findings add new details to the current state of the degrading permafrost. In addition, we observe seismic anisotropy in the frozen permafrost sediments.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029955","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818726","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":"The Role of Microcontinent Strength and Basal Detachment in Accretionary Orogenesis: Insights From Numerical Models","authors":"Zoltan Erdős,&nbsp;Susanne J. H. Buiter,&nbsp;Joya Tetreault","doi":"10.1029/2024JB029509","DOIUrl":"https://doi.org/10.1029/2024JB029509","url":null,"abstract":"<p>During closure of an ocean through subduction and continental collision, bathymetric highs such as microcontinents can accrete, collide, or partially or completely subduct. Such interaction of future allochthonous terranes (FATs) with the overriding continent will modify the dynamics of the subduction zone, affecting its length and frictional resistance, and thus the force balance of the subduction system. Accreted microcontinents and microcontinental fragments are preserved in backarcs and collisional orogens, demonstrating that multiple terranes can accrete during a single Wilson-cycle, in what is termed accretionary orogenesis. In this study, we use thermo-mechanical numerical experiments of microcontinent-continent collision events to investigate parameters that influence whether microcontinents accrete, subduct, or collide. Our results indicate that multiple accretionary episodes are possible, but that a weak basal detachment layer within each FAT is paramount for such a scenario to occur. The introduction of a microcontinent, or FAT, in the subduction zone will affect the balance between slab-pull, far-field forces, and the subduction interface resistance. The strength (and rheological stratification) of the microcontinent determines the evolution of the subduction interface resistance throughout the collision event, exerting a first order control on the resulting geodynamic scenario. Collision with a strong microcontinent significantly increases the subduction interface resistance promoting terrane subduction and localization of deformation away from the subduction interface. In turn, collision with a weak microcontinent increases subduction interface resistance only mildly, allowing for multiple accretion events.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029509","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818728","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":"Quantifying Localized and Delocalized Rock Deformation in Multi-Stage Relaxation Experiments Using Distributed Optical Fiber Sensing","authors":"Shuting Miao,&nbsp;Arno Zang,&nbsp;Pengzhi Pan,&nbsp;Yinlin Ji,&nbsp;Erik Rybacki,&nbsp;Hannes Hofmann,&nbsp;Guido Blöcher,&nbsp;Martin Lipus","doi":"10.1029/2024JB029881","DOIUrl":"https://doi.org/10.1029/2024JB029881","url":null,"abstract":"<p>Multi-stage uniaxial and triaxial stress relaxation tests were performed on Weschnitz granodiorite, Beishan granite, and Jinping dolomite marble to investigate the deformation evolution before system-size failure, and to study stress relaxation responses. Optical fiber sensing was used to measure distributed strain for full-field strain reconstruction across the sample surface. Strain heterogeneities due to imperfect boundary conditions are detected before and during the linear elastic deformation phase in all samples. The initial strain heterogeneity in the elastic phase is found to control the subsequent inelastic strain localization in granodiorite and granite samples. Macroscopic brittle splitting or faulting in granitic samples eventually occurs within or at the boundaries of the strain localization zones. In contrast, dolomite marble has a more homogeneous strain distribution, with increased differential stress promoting strain delocalization. The reduced axial strain rates during stress relaxation promote time-dependent deformation mechanisms, leading to different spatial distributions of strains. Stress relaxation does not significantly change the degree of strain localization in granite, but it promotes strain delocalization in marble after the onset of dilatancy. In multi-stage tests, inelastic strain accumulates mainly during stress relaxation in granite samples and during stress ramping in marble samples. The different strain distributions and relaxation responses between rock samples result from different deformation mechanisms: localized strain in granite results from clustered microcracking, whereas distributed strain in dolomite marble is driven by both microcracking and low-temperature plasticity (e.g., dislocation glide). These results suggest that lithological differences may result in different precursor signals before system-scale failure and postseismic bulk relaxation responses.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029881","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143818730","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":"Topographic Drag at the Core-Mantle Interface","authors":"R. Monville,&nbsp;D. Cébron,&nbsp;D. Jault","doi":"10.1029/2024JB029770","DOIUrl":"10.1029/2024JB029770","url":null,"abstract":"<p>The length of day variations with periods from five to one hundred years are mainly due to core-mantle interactions. Assuming a differential velocity between the core and the mantle, we investigate the pressure coupling on a core-mantle boundary (CMB) interface with topography. Including rotation, buoyancy, and magnetic effects in local models of the CMB, we provide a taxonomy of the waves radiated by the core flow along the topography. We obtain the local stress with a perturbation approach and a semi-analytical spectral model built upon these waves. We incorporate planetary curvature effects by considering a “non-traditional” <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>β</mi>\u0000 </mrow>\u0000 <annotation> $beta $</annotation>\u0000 </semantics></math>-plane approximation suited for deep fluid layers and long topography wavelengths. We calculate weakly non-linear flows and characterize the wave drag mechanism. Unlike previous works, our analysis is not restricted to strong stratification or short wavelengths. It reveals the significant impact of the Rossby waves on stress. We also show that these waves are drastically modified when considering two-dimensional topographies instead of simple ridges. For a buoyancy frequency <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>N</mi>\u0000 </mrow>\u0000 <annotation> $N$</annotation>\u0000 </semantics></math> at least comparable to the rotation frequency, the main factors defining the stress are <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>N</mi>\u0000 </mrow>\u0000 <annotation> $N$</annotation>\u0000 </semantics></math> and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msqrt>\u0000 <msub>\u0000 <mi>U</mi>\u0000 <mn>0</mn>\u0000 </msub>\u0000 </msqrt>\u0000 </mrow>\u0000 <annotation> $sqrt{{U}_{0}}$</annotation>\u0000 </semantics></math> for the small velocity amplitudes <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>U</mi>\u0000 <mn>0</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${U}_{0}$</annotation>\u0000 </semantics></math> relevant for the Earth's core. We document the departures from this scaling law as the velocity is increased. The main part of the CMB pressure torque is due to the topography with the largest horizontal length scale. We calculate the minimum stratification for the topographic torque to produce discernible changes in the length-of-day.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 4","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029770","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143806297","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}