Journal of Geophysical Research: Solid Earth最新文献

{"title":"Understanding the Seismic Signature of Transtensional Opening in the Reykjanes Peninsula Rift Zone, SW Iceland","authors":"Pınar Büyükakpınar,&nbsp;Marius Paul Isken,&nbsp;Sebastian Heimann,&nbsp;Torsten Dahm,&nbsp;Daniela Kühn,&nbsp;Juliane Starke,&nbsp;José Ángel López Comino,&nbsp;Simone Cesca,&nbsp;Jana Doubravová,&nbsp;Egill Árni Gudnason,&nbsp;Thorbjörg Ágústsdóttir","doi":"10.1029/2024JB029566","DOIUrl":"10.1029/2024JB029566","url":null,"abstract":"<p>We analyze seismicity and centroid moment tensors (CMTs) on the Reykjanes Peninsula, Iceland, during the early phase of a widespread unrest period that led to multiple fissure eruptions between 2021 and 2024. We use a dense temporary seismic array, together with fiber-optic distributed acoustic sensing data, and incorporate first-motion polarities into the CMT inversion to improve accuracy, generating a total of 300 robust CMT solutions for magnitudes <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>M</mi>\u0000 <mi>w</mi>\u0000 <mo>&gt;</mo>\u0000 <mn>2.5</mn>\u0000 </mrow>\u0000 <annotation> $Mw &gt; 2.5$</annotation>\u0000 </semantics></math>, focusing on 83 reliable <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>M</mi>\u0000 <mi>w</mi>\u0000 <mo>&gt;</mo>\u0000 <mn>2.7</mn>\u0000 </mrow>\u0000 <annotation> $Mw &gt; 2.7$</annotation>\u0000 </semantics></math> earthquakes for interpretation. The CMTs predominantly exhibit shallow strike-slip faulting, with a few normal faulting events compatible with tectonic stress. Interestingly, significant positive isotropic components are resolved, contributing up to 15% of the moment release. We also develop a new high-resolution seismic catalog of 34,407 events and show that larger shallow earthquakes at the plate boundary are preceded by the slow upward migration of microearthquakes from below, suggesting that intruding magmatic fluids interact with the oblique plate boundary to trigger slow slip events. We interpret our results as the seismic response to transtensional motion at the plate boundary in the brittle upper crust under shear, in response to stress changes induced by the intrusion of pressurized fluids in the lower crust. The complex interaction of multiple subparallel dikes with the plate boundary fault contributes to a broader deformation band that accommodates both tectonic and magmatic stresses. While the location and magnitude of the CMTs correlate with reactivated surface fractures and faults, the locations of intense, deep microseismic swarms indicate the sites of future fissure eruptions.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029566","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905417","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":"Three-Dimensional Unstructured Magnetization Vector Inversion and Modeling of Planetary Equivalent Toroidal Currents for Earth’s Magnetic Field Analysis","authors":"Boxin Zuo,&nbsp;Xiangyun Hu,&nbsp;Lizhe Wang,&nbsp;Yi Cai,&nbsp;Mason Andrew Kass","doi":"10.1029/2024JB029224","DOIUrl":"10.1029/2024JB029224","url":null,"abstract":"<p>This study introduces a pioneering methodology for modeling the Earth’s geomagnetic field, departing from traditional reliance on current loops by employing a three-dimensional (3-D) geometric equivalent toroidal current source. We propose a 3-D unstructured magnetization vector inversion method aimed at inverting the geomagnetic vector field data set to construct an equivalent magnetization source. Subsequently, this constructed source is utilized to solve for the distribution of equivalent toroidal currents. Our objective is to elucidate and analyze potential distributions of toroidal currents within the core space. Diverging from conventional practices that estimate only seven parameters for a current loop, our research undertakes the inversion of millions of current parameters across the entire 3-D core space. This strategy eliminates the need for presuppositions regarding the current’s positions or its topological characteristics, significantly enhancing our capability to depict the possible geometry of toroidal currents. These advancements show considerable promise for modeling the geomagnetic field with high precision, transforming complex equivalent sources into more comprehensible forms, and offering profound implications for our understanding of Earth’s magnetic environment.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142905358","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":"Interseismic Uplift of Anticlines Above the Rakhine-Bangladesh Megathrust From ALOS-2 InSAR","authors":"Jeng-Hann Chong,&nbsp;Bar Oryan,&nbsp;Lin Shen,&nbsp;Michael S. Steckler,&nbsp;Eric O. Lindsey","doi":"10.1029/2024JB030003","DOIUrl":"10.1029/2024JB030003","url":null,"abstract":"<p>The shallow portion of a megathrust represents the zone of first contact between two colliding plates, and its rheological properties control the seismic and tsunami hazards generated by the fault. The high cost of underwater geodetic data collection results in sparse observations, leading to limited constraints on the interseismic behavior of megathrusts. The Rakhine-Bangladesh megathrust offers a unique opportunity to probe the behavior of the shallow megathrust as it is the only ocean-continent subduction zone where the near-trench region is fully accessible on land. Here, we use observations from ALOS-2 wide-swath imagery spanning 2015 to 2022 to conduct an InSAR timeseries analysis of the overriding plate within Bangladesh and the Indo-Myanmar Ranges. We identify a narrow pattern of alternating uplift and subsidence associated with mapped anticlines but show that it cannot be explained by slip on the megathrust or other fault structures. Instead, we argue that the deformation is likely caused by active aseismic folding within the wedge above a shallow decollement. We show that estimates of the decollement depth derived from a viscous folding model and the observed anticline spacing are in agreement with previous seismic observations of the decollement depth across the fold belt. We suggest that the role of ductile deformation in the overriding plate in subduction zones may be more important than previously recognized.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142902235","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":"Constraints on the Seismogenic Stress Tensor in Northeastern South Island, New Zealand","authors":"Olivia Leigh Walbert,&nbsp;Eric Andreas Hetland","doi":"10.1029/2024JB028877","DOIUrl":"10.1029/2024JB028877","url":null,"abstract":"<p>The seismogenic tensorial stresses in the crust beneath northeastern South Island, New Zealand that are responsible for the 2010 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>M</mi>\u0000 <mi>w</mi>\u0000 </msub>\u0000 <mn>7.2</mn>\u0000 </mrow>\u0000 <annotation> ${M}_{w}7.2$</annotation>\u0000 </semantics></math> Darfield and 22 February 2011 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>M</mi>\u0000 <mi>w</mi>\u0000 </msub>\u0000 <mn>6.2</mn>\u0000 </mrow>\u0000 <annotation> ${M}_{w}6.2$</annotation>\u0000 </semantics></math> Christchurch earthquakes of the Canterbury Plains, South Island, New Zealand are compatible with an Andersonian strike-slip regime with a NW–SE trending most compressive stress. The stresses we infer from coseismic slip models of these two earthquakes are consistent with previous estimates of stress from earthquake focal mechanisms near the Alpine Fault. The strike-slip stress regime of the Canterbury Plains differs from the thrust stress regime that we previously estimated from coseismic models of the 2016 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>M</mi>\u0000 <mi>w</mi>\u0000 </msub>\u0000 <mn>7.8</mn>\u0000 </mrow>\u0000 <annotation> ${M}_{w}7.8$</annotation>\u0000 </semantics></math> Kaikōura earthquake. We demonstrate that loading due to thick sediment deposits overlying the crust of the Canterbury Plains is a sufficient mechanism to rotate the principal stresses from a background thrust regime to a strike-slip regime, constraining the absolute tectonic stress in the northeast of South Island to most likely be <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math> 26 MPa, and no larger than <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math> 80 MPa.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB028877","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142902237","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":"Extracting Site Effects From P-wave spectra: Application of Cluster-Event Method 2 (CEM2) in the Tohoku Region, Japan","authors":"Pei-Ru Jian,&nbsp;Ban-Yuan Kuo","doi":"10.1029/2024JB028955","DOIUrl":"10.1029/2024JB028955","url":null,"abstract":"<p>Theories related to the Earth's attenuation effect and earthquake source properties predict a similar spectral falloff of body waves, creating severe trade-off problems when determining these two processes from waveform spectra. Previous efforts attempted to suppress this trade-off by either applying an empirical Green's function or conducting linear inversion with a specially designed event–station configuration. However, both approaches encounter difficulties when dealing with large datasets or site effect contamination. In this study, we modify a previously used cluster-event method (CEM), combining both the spectral amplitude and the spectral ratio of the P-waves for the clustering of events (CEM2); we then apply CEM2 to the High-Sensitivity Seismograph Network data in the Tohoku region of Japan. An initial inversion with CEM2 yields the first estimates of the source and path parameters, that is, the corner frequency (<i>f</i>_<i>c</i>) and the quality factor (<i>Q</i>). The residuals of this inversion demonstrate distinct spectral characteristics that are well correlated with vertical-to-horizontal (V/H) spectral ratios of the P-coda waves at each station, suggesting that they represent a form of site response unaccounted for by theoretical predictions of <i>Q</i> and <i>f</i>_<i>c</i>. After removing this particular site response, the second inversion yields an improved determination of <i>Q</i>. We hypothesize that this site effect is dominated by P to SV conversion upon P-wave arrival and develops and amplifies toward the coda waves. Furthermore, the site effect demonstrates systematic regional characteristics, some of which correlate well with those derived from the V/H spectral ratios of the P-coda waves.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB028955","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888441","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":"Stabilized Unfitted Finite Element Method for Poroelasticity With Weak Discontinuity","authors":"Zhijun Liu,&nbsp;Yuxin Tong,&nbsp;Yimin Zhang,&nbsp;Hong Zheng,&nbsp;Fanyu Zhang","doi":"10.1029/2024JB030155","DOIUrl":"10.1029/2024JB030155","url":null,"abstract":"<p>Poromechanics problems in geotechnical and geological contexts often involve complex formations with numerous boundaries and material interfaces, which significantly complicate numerical analysis and simulation. The traditional finite element method (FEM) encounters substantial challenges in these scenarios because it requires the mesh to conform precisely to each boundary and interface. This requirement complicates preprocessing and necessitates meticulous manual control to achieve a high-quality mesh. In contrast, unfitted FEMs are well-suited for these problems as they do not require the mesh to align with the model geometry. We propose a stabilized unfitted FEM that incorporates Nitsche's method and ghost penalty stabilization techniques to address complex poroelasticity problems. This approach treats material interfaces as weak discontinuities and ensures that compatibility conditions are satisfied. The proposed method allows the mesh to be independent of both boundaries and material interfaces. Nitsche's method is used to weakly enforce both Dirichlet boundary conditions and interface compatibility conditions, resulting in a symmetric weak form. Additionally, three types of ghost penalty terms are introduced for elements intersected by boundaries or interfaces, effectively eliminating cut-induced ill-conditioning. The proposed methodology has been validated through benchmark and practical problems, demonstrating optimal convergence and exceptional stability. This approach significantly enhances the stability and efficiency of hydro-mechanical analyses for complex geotechnical and geological problems.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888446","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":"Beyond the Average: Computation of Vertical Profiles in Dilute Pyroclastic Density Currents and Their Use in Shallow-Water Models","authors":"B. Keim,&nbsp;M. de’ Michieli Vitturi","doi":"10.1029/2024JB029975","DOIUrl":"10.1029/2024JB029975","url":null,"abstract":"<p>Pyroclastic density currents (PDCs) present significant hazards due to their high temperatures and dynamic pressures. Accurate estimation of dynamic pressure, vital for assessing potential damage, requires knowledge of the vertical variations of velocity and particle concentration within the PDC, particularly in the first few meters of the flow above the ground. Existing approaches to dynamic pressure calculations used in hazard assessment are often based on average values for velocity and particle volume fraction. These average values may misrepresent the flow dynamics, especially near the base of the flow where the gradients of flow variables are larger. Here, we present a new, physically based approach that allows for the calculation of the vertical profiles of velocity and concentration from a combination of depth-averaged values for these properties and non-dimensional flow parameters. Finally, we demonstrate the use of these profiles within an existing shallow-water model and show its potential applications toward probabilistic hazard assessment.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029975","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887175","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":"Earthquake Nucleation and Slip Behavior Altered by Stochastic Normal Stress Heterogeneity","authors":"Meng Li,&nbsp;Andre Niemeijer,&nbsp;Ylona van Dinther","doi":"10.1029/2024JB029857","DOIUrl":"10.1029/2024JB029857","url":null,"abstract":"&lt;p&gt;In recent laboratory experiments, varying nucleation locations of accelerating slip with changing nucleation lengths were observed. Spatial variations in effective normal stress, due to the controlling influence on fault strength and fracture energy, play an important role. We quantitatively explain how spatially heterogeneous effective normal stresses affect earthquake nucleation and slip behavior. We simulate a meter-scale laboratory experiment in a numerical earthquake sequence model with stochastically variable normal stresses. We identify five regimes of earthquake nucleation and slip behaviors, controlled by the ratio of the heterogeneity wavelength &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;(&lt;/mo&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;mo&gt;)&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $(lambda )$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; to the nucleation length &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mfenced&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mi&gt;c&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mfenced&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $left({L}_{c}right)$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. When &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mi&gt;c&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;≪&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $lambda /{L}_{c}ll 1$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, full ruptures are observed. Slip rates and recurrence intervals are similar to those on homogeneous faults with comparable averaged normal stress. When &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;L&lt;/mi&gt;\u0000 &lt;mi&gt;c&lt;/mi&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mo&gt;≫&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $lambda /{L}_{c}gg 1$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, slow slip events and partial ruptures occur frequently and the nucleation length of each earthquake depends on the local stress level. We find locations of nucleation and arrest in both low and high normal stress regions (LSR and HSR, respectively) when &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $lambda $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 ","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029857","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887177","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":"Late Cretaceous Ophiolite Emplacement and Cenozoic Collisional Tectonics in the Northeastern Arabian Plate: Insights From New Broadband Magnetotelluric Data","authors":"B. A. Cherkose,&nbsp;H. Saibi,&nbsp;K. Al Bloushi,&nbsp;M. Y. Ali,&nbsp;A. Fowler,&nbsp;M. Smirnov","doi":"10.1029/2024JB028744","DOIUrl":"10.1029/2024JB028744","url":null,"abstract":"<p>The Late Cretaceous obduction of the Semail Ophiolite onto the rifted passive Arabian margin and the Cenozoic collisional tectonics with the final closure of the Neo-Tethys Ocean, are major contributors to the present-day crustal architecture of the northern United Arab Emirates (UAE). We acquired the first 3D grid magnetotelluric observations from 73 stations in the northern UAE in order to image deep crustal electrical structures associated with the two significant compressional episodes. Inversion of the broadband magnetotelluric data reveals the subsurface geometry of the high-resistivity ophiolite blocks, the underlying conductive thrust sheet (Haybi-Hawasina nappe), a “wedge-shaped” conductive foreland basin flanking the Hajar mountain ranges, and at depth, a high-resistivity structure associated with a fold-thrust belt adjacent to the allochthonous units, or Proterozoic crystalline basement. The ophiolite along the eastern coast (from cities Khor Fakkan to Fujairah) is more than 20 km thick and dips eastward. Across the Wadi Ham fault, the resistive ophiolite lies against less resistive materials that may represent Bani Hamid metamorphic rocks. The thin-skinned thrust sheets of the proximal-distal Tethyan sedimentary units (Haybi-Hawasina complexes) exhibit low resistivity in the Dibba zone. In contrast to its gently east-dipping geometry in the Dibba zone, the conductive Haybi-Hawasina structure in the southern portion of the study area appears nearly vertically (&gt;20 km) beneath the dense Khor Fakkan and Aswad ophiolite blocks. This result suggests extensive deformation of the thrust sheets beneath the southerly dense ophiolite blocks.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB028744","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887174","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 Effects of Characteristic Weakening Distance on Earthquake Nucleation Styles in Fully Dynamic Seismic Cycle Simulations","authors":"Peng Zhai,&nbsp;Yihe Huang","doi":"10.1029/2024JB029719","DOIUrl":"10.1029/2024JB029719","url":null,"abstract":"&lt;p&gt;Earthquake nucleation is a crucial preparation process of the following coseismic rupture propagation. Under the framework of rate-and-state friction (RSF), it was found that the ratios of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $a$&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;mi&gt;b&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $b$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; parameters control whether earthquakes nucleate as an expanding crack or with a fixed length prior to the dynamic instability. However, the characteristic weakening distance &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;D&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${D}_{RS}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; controls the weakening efficiency of state variables in RSF and can influence the nucleation styles as well. Here we investigate the effects 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;D&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${D}_{RS}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; on nucleation styles in the context of fully dynamic seismic cycles by evaluating the evolution of the nucleation zone quantitatively when it accelerates from the tectonic loading rate to seismic slip velocity. A larger &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;a&lt;/mi&gt;\u0000 &lt;mo&gt;/&lt;/mo&gt;\u0000 &lt;mi&gt;b&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $a/b$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; (&gt;0.75) is needed to produce expanding crack nucleation styles for relatively small &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;D&lt;/mi&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;R&lt;/mi&gt;\u0000 &lt;mi&gt;S&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${D}_{RS}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, which suggests that fixed length nucleation styles may dominate on natural and laboratory faults. Furthermore, we find a more complex nucleation style when the nucleation site is not in the center of the asperity and ","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"129 12","pages":""},"PeriodicalIF":3.9,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JB029719","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142880123","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}