Abstract. The seismogenesis of rocks is mainly affected by their mineral composition and in situ conditions (temperature and state of stress). Diverse laboratory experiments have explored the frictional behaviour of the rocks and rock-forming minerals most common in the crust and uppermost mantle. However, it is debated how to “upscale” these results to the lithosphere. In particular, most earthquakes in the crust nucleate down to the crustal seismogenic depth (CSD), which is a proxy for the maximum depth of crustal earthquake ruptures in seismic hazard assessments. In this study we propose a workflow to upscale and validate those laboratory experiments to natural geological conditions relevant for crustal and upper-mantle rocks. We used the southern Caribbean and northwestern South America as a case study to explore the three-dimensional spatial variation of the CSD (mapped as D90, the 90 % percentile of hypocentral depths) and the temperatures at which crustal earthquakes likely occur. A 3D steady-state thermal field was computed for the region with a finite-element scheme using the software GOLEM, considering the uppermost 75 km of a previously published 3D data-integrative lithospheric configuration, lithology-constrained thermal parameters, and appropriate upper and lower boundary conditions. The model was validated using additional, independent measurements of downhole temperatures and heat flow. We found that the majority of crustal earthquakes nucleate at temperatures less than 350 ∘C, in agreement with frictional experiments of typical crustal rocks. A few outliers with larger hypocentral temperatures evidence nucleation conditions consistent with the seismogenic window of olivine-rich rocks, and can be due to either uncertainties in the Moho depths and/or in the earthquake hypocentres or the presence of ultramafic rocks within different crustal blocks and allochthonous terranes accreted to this complex margin. Moreover, the spatial distribution of crustal seismicity in the region correlates with the geothermal gradient, with no crustal earthquakes occurring in domains with low thermal gradient. Finally, we find that the largest earthquake recorded in the region (Mw=7.1, Murindó sequence, in 1992) nucleated close to the CSD, highlighting the importance of considering this lower-stability transition for seismogenesis when characterizing the depth of seismogenic sources in hazard assessments. The approach presented in this study goes beyond a statistical approach in that the local heterogeneity of physical properties is considered in our simulations and additionally validated by the observed depth distribution of earthquakes. The coherence of the calculated hypocentral temperatures with those expected from laboratory measurements provides additional support to our modelling workflow. This approach can be applied to other tectonic settings worldwide, and it could be further refined as new, high-quality hypocentral locations and heat flow an
{"title":"Thermal structure of the southern Caribbean and northwestern South America: implications for seismogenesis","authors":"Ángela María Gómez-García, Álvaro González, Mauro Cacace, Magdalena Scheck-Wenderoth, Gaspar Monsalve","doi":"10.5194/se-15-281-2024","DOIUrl":"https://doi.org/10.5194/se-15-281-2024","url":null,"abstract":"Abstract. The seismogenesis of rocks is mainly affected by their mineral composition and in situ conditions (temperature and state of stress). Diverse laboratory experiments have explored the frictional behaviour of the rocks and rock-forming minerals most common in the crust and uppermost mantle. However, it is debated how to “upscale” these results to the lithosphere. In particular, most earthquakes in the crust nucleate down to the crustal seismogenic depth (CSD), which is a proxy for the maximum depth of crustal earthquake ruptures in seismic hazard assessments. In this study we propose a workflow to upscale and validate those laboratory experiments to natural geological conditions relevant for crustal and upper-mantle rocks. We used the southern Caribbean and northwestern South America as a case study to explore the three-dimensional spatial variation of the CSD (mapped as D90, the 90 % percentile of hypocentral depths) and the temperatures at which crustal earthquakes likely occur. A 3D steady-state thermal field was computed for the region with a finite-element scheme using the software GOLEM, considering the uppermost 75 km of a previously published 3D data-integrative lithospheric configuration, lithology-constrained thermal parameters, and appropriate upper and lower boundary conditions. The model was validated using additional, independent measurements of downhole temperatures and heat flow. We found that the majority of crustal earthquakes nucleate at temperatures less than 350 ∘C, in agreement with frictional experiments of typical crustal rocks. A few outliers with larger hypocentral temperatures evidence nucleation conditions consistent with the seismogenic window of olivine-rich rocks, and can be due to either uncertainties in the Moho depths and/or in the earthquake hypocentres or the presence of ultramafic rocks within different crustal blocks and allochthonous terranes accreted to this complex margin. Moreover, the spatial distribution of crustal seismicity in the region correlates with the geothermal gradient, with no crustal earthquakes occurring in domains with low thermal gradient. Finally, we find that the largest earthquake recorded in the region (Mw=7.1, Murindó sequence, in 1992) nucleated close to the CSD, highlighting the importance of considering this lower-stability transition for seismogenesis when characterizing the depth of seismogenic sources in hazard assessments. The approach presented in this study goes beyond a statistical approach in that the local heterogeneity of physical properties is considered in our simulations and additionally validated by the observed depth distribution of earthquakes. The coherence of the calculated hypocentral temperatures with those expected from laboratory measurements provides additional support to our modelling workflow. This approach can be applied to other tectonic settings worldwide, and it could be further refined as new, high-quality hypocentral locations and heat flow an","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"4 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769866","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}
Pub Date : 2024-02-15DOI: 10.5194/egusphere-2024-435
Maxime Jamet, Gregory Ballas, Roger Soliva, Olivier Gerbeaud, Thierry Lefebvre, Christine Leredde, Didier Loggia
Abstract. This study delves into the characterization of a complex reservoir, the Tchirezrine II sandstone unit in North Niger, crucial for potential Uranium In Situ Recovery (ISR) in a naturally fractured and faulted context. Employing a multifaceted approach, including well log data, optical borehole imagery, and hydrogeological tests, alongside satellite-based lineament analysis, this study provides a comprehensive understanding of the structures and its impact on fluid flow. Lineament analysis reveals scale-dependent patterns, consistent with spatially homogeneous joint networks restricted to mechanical units, as well as nearly scale-invariant patterns, better corresponding to spatially heterogeneous fault networks. Various deformation structures are detected from borehole imagery, including Mode I fractures, cataclastic deformation bands, and brecciated-cataclastic fault cores. The Tchirezrine II reservoir displays heterogeneous porosity and permeability related to its fluviatile sedimentary context. These data differ from traditional porosity-permeability relationship obtained in sandstone reservoir matrix but are instead consistent with Nelson’s classification, emphasizing the impact of deformation structures on such petrophysical properties. Hydrological tests have been implemented into a zone of E-W trending deformation structures, revealing a strong permeability anisotropy of this heterogeneity. This strong E-W anisotropy is consistent with the presence of the observed E-W structures, i.e. with a drain behaviour of Mode I open fractures and a sealing behaviour of both cataclastic bands and fault rocks. Considering implications for ISR mining, this study allows discussing the interplay between fractures, faults, and fluid flow properties. It suggests that a well pattern perpendicular to the main permeability orientation can attenuate channelled flow, thus improving contact of the leach solution with the mineralized matrix. These results provide an integrated approach and multi-scale characterization of NaturallyFractured Reservoir (NFR) properties in sandstone, offering a basis for optimization of NFR production such as ISR development.
摘要本研究深入探讨了尼日尔北部 Tchirezrine II 砂岩单元这一复杂储层的特征，这对于在自然断裂和断层背景下进行潜在的铀原位采收（ISR）至关重要。这项研究采用了多方面的方法，包括测井数据、井眼光学图像和水文地质测试，以及基于卫星的线状分析，全面了解了结构及其对流体流动的影响。线状分析揭示了与尺度相关的模式，与局限于力学单元的空间均质联合网络相一致，同时也揭示了几乎与尺度无关的模式，更符合空间异质断层网络。从钻孔图像中探测到了各种变形结构，包括模式 I 断裂、碎屑岩变形带和碎屑-碎屑岩断层核心。Tchirezrine II 储层显示出与其流化沉积背景相关的异质性孔隙度和渗透率。这些数据不同于在砂岩储层基质中获得的传统孔隙度-渗透率关系，而是与纳尔逊分类法一致，强调了变形结构对此类岩石物理特性的影响。在 E-W 向变形结构区进行了水文测验，发现这种异质性具有很强的渗透率各向异性。这种强烈的 E-W 向各向异性与观测到的 E-W 结构的存在是一致的，即与模式 I 开口裂缝的排泄行为以及 cataclastic 带和断层岩的密封行为是一致的。考虑到对 ISR 采矿的影响，这项研究有助于讨论断裂、断层和流体流动特性之间的相互作用。研究表明，垂直于主要渗透方向的井型可以减弱导流，从而改善浸出液与矿化基质的接触。这些结果提供了一种综合方法和砂岩天然裂缝储层（NFR）特性的多尺度表征，为优化天然裂缝储层生产（如 ISR 开发）提供了基础。
{"title":"Naturally fractured reservoir characterization in heterogeneous sandstones: insight for Uranium In Situ Recovery (Imouraren, Niger)","authors":"Maxime Jamet, Gregory Ballas, Roger Soliva, Olivier Gerbeaud, Thierry Lefebvre, Christine Leredde, Didier Loggia","doi":"10.5194/egusphere-2024-435","DOIUrl":"https://doi.org/10.5194/egusphere-2024-435","url":null,"abstract":"<strong>Abstract.</strong> This study delves into the characterization of a complex reservoir, the Tchirezrine II sandstone unit in North Niger, crucial for potential Uranium In Situ Recovery (ISR) in a naturally fractured and faulted context. Employing a multifaceted approach, including well log data, optical borehole imagery, and hydrogeological tests, alongside satellite-based lineament analysis, this study provides a comprehensive understanding of the structures and its impact on fluid flow. Lineament analysis reveals scale-dependent patterns, consistent with spatially homogeneous joint networks restricted to mechanical units, as well as nearly scale-invariant patterns, better corresponding to spatially heterogeneous fault networks. Various deformation structures are detected from borehole imagery, including Mode I fractures, cataclastic deformation bands, and brecciated-cataclastic fault cores. The Tchirezrine II reservoir displays heterogeneous porosity and permeability related to its fluviatile sedimentary context. These data differ from traditional porosity-permeability relationship obtained in sandstone reservoir matrix but are instead consistent with Nelson’s classification, emphasizing the impact of deformation structures on such petrophysical properties. Hydrological tests have been implemented into a zone of E-W trending deformation structures, revealing a strong permeability anisotropy of this heterogeneity. This strong E-W anisotropy is consistent with the presence of the observed E-W structures, i.e. with a drain behaviour of Mode I open fractures and a sealing behaviour of both cataclastic bands and fault rocks. Considering implications for ISR mining, this study allows discussing the interplay between fractures, faults, and fluid flow properties. It suggests that a well pattern perpendicular to the main permeability orientation can attenuate channelled flow, thus improving contact of the leach solution with the mineralized matrix. These results provide an integrated approach and multi-scale characterization of Naturally<strong> </strong>Fractured Reservoir (NFR) properties in sandstone, offering a basis for optimization of NFR production such as ISR development.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"127 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769929","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}
Fabian Kutschera, Alice-Agnes Gabriel, Sara Aniko Wirp, Bo Li, Thomas Ulrich, Claudia Abril, Benedikt Halldórsson
Abstract. Tsunamigenic earthquakes pose considerable risks, both economically and socially, yet earthquake and tsunami hazard assessments are typically conducted separately. Earthquakes associated with unexpected tsunamis, such as the 2018 Mw 7.5 strike-slip Sulawesi earthquake, emphasize the need to study the tsunami potential of active submarine faults in different tectonic settings. Here, we investigate physics-based scenarios combining simulations of 3D earthquake dynamic rupture and seismic wave propagation with tsunami generation and propagation. We present time-dependent modeling of one-way linked and 3D fully coupled earthquakes and tsunamis for the ∼ 100 km long Húsavík–Flatey Fault Zone (HFFZ) in North Iceland. Our analysis shows that the HFFZ has the potential to generate sizable tsunamis. The six dynamic rupture models sourcing our tsunami scenarios vary regarding hypocenter location, spatiotemporal evolution, fault slip, and fault structure complexity but coincide with historical earthquake magnitudes. Earthquake dynamic rupture scenarios on a less segmented fault system, particularly with a hypocenter location in the eastern part of the fault system, have a larger potential for local tsunami generation. Here, dynamically evolving large shallow fault slip (∼ 8 m), near-surface rake rotation (± 20∘), and significant coseismic vertical displacements of the local bathymetry (± 1 m) facilitate strike-slip faulting tsunami generation. We model tsunami crest to trough differences (total wave heights) of up to ∼ 0.9 m near the town Ólafsfjörður. In contrast, none of our scenarios endanger the town of Akureyri, which is shielded by multiple reflections within the narrow Eyjafjörður bay and by Hrísey island. We compare the modeled one-way linked tsunami waveforms with simulation results using a 3D fully coupled approach. We find good agreement in the tsunami arrival times and location of maximum tsunami heights. While seismic waves result in transient motions of the sea surface and affect the ocean response, they do not appear to contribute to tsunami generation. However, complex source effects arise in the fully coupled simulations, such as tsunami dispersion effects and the complex superposition of seismic and acoustic waves within the shallow continental shelf of North Iceland. We find that the vertical velocity amplitudes of near-source acoustic waves are unexpectedly high – larger than those corresponding to the actual tsunami – which may serve as a rapid indicator of surface dynamic rupture. Our results have important implications for understanding the tsunamigenic potential of strike-slip fault systems worldwide and the coseismic acoustic wave excitation during tsunami generation and may help to inform future tsunami early warning systems.
{"title":"Linked and fully coupled 3D earthquake dynamic rupture and tsunami modeling for the Húsavík–Flatey Fault Zone in North Iceland","authors":"Fabian Kutschera, Alice-Agnes Gabriel, Sara Aniko Wirp, Bo Li, Thomas Ulrich, Claudia Abril, Benedikt Halldórsson","doi":"10.5194/se-15-251-2024","DOIUrl":"https://doi.org/10.5194/se-15-251-2024","url":null,"abstract":"Abstract. Tsunamigenic earthquakes pose considerable risks, both economically and socially, yet earthquake and tsunami hazard assessments are typically conducted separately. Earthquakes associated with unexpected tsunamis, such as the 2018 Mw 7.5 strike-slip Sulawesi earthquake, emphasize the need to study the tsunami potential of active submarine faults in different tectonic settings. Here, we investigate physics-based scenarios combining simulations of 3D earthquake dynamic rupture and seismic wave propagation with tsunami generation and propagation. We present time-dependent modeling of one-way linked and 3D fully coupled earthquakes and tsunamis for the ∼ 100 km long Húsavík–Flatey Fault Zone (HFFZ) in North Iceland. Our analysis shows that the HFFZ has the potential to generate sizable tsunamis. The six dynamic rupture models sourcing our tsunami scenarios vary regarding hypocenter location, spatiotemporal evolution, fault slip, and fault structure complexity but coincide with historical earthquake magnitudes. Earthquake dynamic rupture scenarios on a less segmented fault system, particularly with a hypocenter location in the eastern part of the fault system, have a larger potential for local tsunami generation. Here, dynamically evolving large shallow fault slip (∼ 8 m), near-surface rake rotation (± 20∘), and significant coseismic vertical displacements of the local bathymetry (± 1 m) facilitate strike-slip faulting tsunami generation. We model tsunami crest to trough differences (total wave heights) of up to ∼ 0.9 m near the town Ólafsfjörður. In contrast, none of our scenarios endanger the town of Akureyri, which is shielded by multiple reflections within the narrow Eyjafjörður bay and by Hrísey island. We compare the modeled one-way linked tsunami waveforms with simulation results using a 3D fully coupled approach. We find good agreement in the tsunami arrival times and location of maximum tsunami heights. While seismic waves result in transient motions of the sea surface and affect the ocean response, they do not appear to contribute to tsunami generation. However, complex source effects arise in the fully coupled simulations, such as tsunami dispersion effects and the complex superposition of seismic and acoustic waves within the shallow continental shelf of North Iceland. We find that the vertical velocity amplitudes of near-source acoustic waves are unexpectedly high – larger than those corresponding to the actual tsunami – which may serve as a rapid indicator of surface dynamic rupture. Our results have important implications for understanding the tsunamigenic potential of strike-slip fault systems worldwide and the coseismic acoustic wave excitation during tsunami generation and may help to inform future tsunami early warning systems.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"15 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769842","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}
Abstract. We derived scaling relationships for different seismic energy metrics for earthquakes around the globe with MW > 6.0 from 1990 to 2022. The seismic energy estimations were derived with two methodologies, the first based on the velocity flux integration and the second based on finite-fault models. In the first case, we analyzed 3331 reported seismic energies derived by integrating far-field waveforms. In the latter methodology, we used the total moment rate functions and the approximation of the overdamped dynamics to quantify seismic energy from 231 finite-fault models (Emrt and EO, EU, respectively). Both methodologies provide compatible energy estimates. The radiated seismic energies estimated from the slip models and integration of velocity records are also compared for different types of focal mechanisms (R, reverse; R-SS, reverse–strike-slip; SS, strike-slip; SS-R, strike-slip–reverse; SS-N, strike-slip–normal; N, normal; and N-SS, normal–strike-slip), and then used to derive converting scaling relations among the different energy types. Additionally, the behavior of radiated seismic energy (ER), energy-to-moment ratio (ER/M0), and apparent stress (τα) for different rupture types at a global scale is examined by considering depth variations in mechanical properties, such as seismic velocities, rock densities, and rigidities. For this purpose, we used a 1-D global velocity model. The ER/M0 ratio is, based on statistical t tests, largest for strike-slip earthquakes, followed by normal-faulting events, with the lowest values for reverse earthquakes for hypocentral depths < 90 km. Not enough data are available for statistical tests at deeper intervals except for the 90 to 120 km range, where we can satisfactorily conclude that ER/M0 for R-SS and SS-R types is larger than for N-type faulting, which also conforms to the previous assumption. In agreement with previous studies, our results exhibit a robust variation in τα with the focal mechanism. Regarding the behavior of τα with depth, our results agree with the existence of a bimodal distribution with two depth intervals where the apparent stress is maximum for normal-faulting earthquakes. At depths in the range of 180–240 km, τα for reverse earthquakes is higher than for normal-faulting events. We find the trend EU > Emrt > EO for all mechanism types based on statistical t tests. Finite-fault energy estimations also support focal mechanism dependence of apparent stress but only for shallow earthquakes (Z < 30 km). The slip distribution population used was too small to conclude that finite-fault energy estimations support the dependence of average apparent stress on rupture type at different depth intervals.
摘要我们推导了 1990 年至 2022 年全球发生的 MW > 6.0 地震的不同地震能量指标的比例关系。地震能量估算有两种方法，第一种基于速度通量积分，第二种基于有限断层模型。在第一种方法中，我们分析了 3331 次报告的地震能量，这些地震能量是通过整合远场波形得出的。在后一种方法中，我们使用总力矩率函数和过阻尼动力学近似值来量化来自 231 个有限断层模型（分别为 Emrt 和 EO，EU）的地震能量。这两种方法都提供了兼容的能量估算。通过滑动模型和速度记录积分估算的辐射地震能量还针对不同类型的病灶机制（R，反向；R-SS，反向-打击-滑动；SS，打击-滑动；SS-R，打击-滑动-反向；SS-N，打击-滑动-正常；N，正常；N-SS，正常-打击-滑动）进行了比较，然后用于推导不同能量类型之间的转换比例关系。此外，通过考虑地震速度、岩石密度和刚度等力学特性的深度变化，研究了全球范围内不同断裂类型的辐射地震能量（ER）、能量-时刻比（ER/M0）和表观应力（τα）的行为。为此，我们使用了一维全球速度模型。根据统计 t 检验，ER/M0 比值最大的是走向滑动地震，其次是正断层地震，而根据统计 t 检验，在所有机制类型中，下中心深度 Emrt > EO 的反向地震的ER/M0 比值最小。有限断层能量估算也支持视应力的焦点机制依赖性，但仅适用于浅层地震（Z < 30 km）。由于使用的滑动分布群太小，因此无法得出有限断层能量估计支持不同深度区间的平均视应力与断裂类型有关的结论。
{"title":"Global seismic energy scaling relationships based on the type of faulting","authors":"Quetzalcoatl Rodríguez-Pérez, F. Ramón Zúñiga","doi":"10.5194/se-15-229-2024","DOIUrl":"https://doi.org/10.5194/se-15-229-2024","url":null,"abstract":"Abstract. We derived scaling relationships for different seismic energy metrics for earthquakes around the globe with MW > 6.0 from 1990 to 2022. The seismic energy estimations were derived with two methodologies, the first based on the velocity flux integration and the second based on finite-fault models. In the first case, we analyzed 3331 reported seismic energies derived by integrating far-field waveforms. In the latter methodology, we used the total moment rate functions and the approximation of the overdamped dynamics to quantify seismic energy from 231 finite-fault models (Emrt and EO, EU, respectively). Both methodologies provide compatible energy estimates. The radiated seismic energies estimated from the slip models and integration of velocity records are also compared for different types of focal mechanisms (R, reverse; R-SS, reverse–strike-slip; SS, strike-slip; SS-R, strike-slip–reverse; SS-N, strike-slip–normal; N, normal; and N-SS, normal–strike-slip), and then used to derive converting scaling relations among the different energy types. Additionally, the behavior of radiated seismic energy (ER), energy-to-moment ratio (ER/M0), and apparent stress (τα) for different rupture types at a global scale is examined by considering depth variations in mechanical properties, such as seismic velocities, rock densities, and rigidities. For this purpose, we used a 1-D global velocity model. The ER/M0 ratio is, based on statistical t tests, largest for strike-slip earthquakes, followed by normal-faulting events, with the lowest values for reverse earthquakes for hypocentral depths < 90 km. Not enough data are available for statistical tests at deeper intervals except for the 90 to 120 km range, where we can satisfactorily conclude that ER/M0 for R-SS and SS-R types is larger than for N-type faulting, which also conforms to the previous assumption. In agreement with previous studies, our results exhibit a robust variation in τα with the focal mechanism. Regarding the behavior of τα with depth, our results agree with the existence of a bimodal distribution with two depth intervals where the apparent stress is maximum for normal-faulting earthquakes. At depths in the range of 180–240 km, τα for reverse earthquakes is higher than for normal-faulting events. We find the trend EU > Emrt > EO for all mechanism types based on statistical t tests. Finite-fault energy estimations also support focal mechanism dependence of apparent stress but only for shallow earthquakes (Z < 30 km). The slip distribution population used was too small to conclude that finite-fault energy estimations support the dependence of average apparent stress on rupture type at different depth intervals.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"30 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769853","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}
Pub Date : 2024-02-12DOI: 10.5194/egusphere-2024-299
Manuele Faccenda, Brandon Paul VanderBeek, Albert de Montserrat, Jianfeng Yang, Neil Ribe
Abstract. Mechanical anisotropy related to rock fabrics is a proxy for constraining the Earth’s deformation patterns. However, the forward and inverse modelling of mechanical anisotropy in 3D large-scale domains has been traditionally hampered by the intensive computational cost and the lack of a dedicated, open-source computational framework. Here we introduce ECOMAN, a software package for modelling strain-/stress-induced rock fabrics and testing the effects of the resulting elastic and viscous anisotropy on seismic imaging and mantle convection patterns. Differently from existing analogous software, the modelling of strain-induced fabrics has been extended to all mantle levels and it has been optimised to run across multiple CPUs, yielding strong scaling efficiency. In addition, shape preferred orientation (SPO)-related structures can be modelled and superimposed over lattice/crystallographic preferred orientation (LPO/CPO) fabrics, which allows the consideration of the mechanical effects of fluid-filled cracks, foliated/lineated grain-scale fabrics and rock-scale layering. One of the most important innovations is the Platform for Seismic Imaging (PSI), a set of programs for performing forward and inverse seismic modelling in isotropic/anisotropic media using real or synthetic seismic datasets. The anisotropic inversion strategy is capable of recovering parameters describing a tilted transversely isotropic (TTI) medium, which is required to reconstruct 3D structures and mantle strain patterns and to validate geodynamic models.
摘要与岩石结构相关的力学各向异性是制约地球变形模式的一种替代方法。然而，三维大尺度域中机械各向异性的正演和反演建模历来受制于高昂的计算成本和缺乏专用的开源计算框架。在此，我们介绍 ECOMAN 软件包，该软件包用于模拟应变/应力引起的岩石结构，并测试由此产生的弹性和粘性各向异性对地震成像和地幔对流模式的影响。与现有的类似软件不同的是，应变诱导构造的建模已扩展到所有地幔层，并对其进行了优化，以便在多个 CPU 上运行，从而产生很高的扩展效率。此外，与形状优选取向（SPO）相关的结构也可以建模，并叠加在晶格/晶体学优选取向（LPO/CPO）结构之上，从而可以考虑充满流体的裂缝、叶状/线状晶粒尺度结构和岩石尺度分层的力学效应。最重要的创新之一是地震成像平台（PSI），这是一套利用真实或合成地震数据集在各向同性/各向异性介质中执行正演和反演地震建模的程序。各向异性反演策略能够恢复描述倾斜横向各向同性（TTI）介质的参数，这是重建三维结构和地幔应变模式以及验证地球动力学模型所必需的。
{"title":"ECOMAN: an open-source package for geodynamic and seismological modeling of mechanical anisotropy","authors":"Manuele Faccenda, Brandon Paul VanderBeek, Albert de Montserrat, Jianfeng Yang, Neil Ribe","doi":"10.5194/egusphere-2024-299","DOIUrl":"https://doi.org/10.5194/egusphere-2024-299","url":null,"abstract":"<strong>Abstract.</strong> Mechanical anisotropy related to rock fabrics is a proxy for constraining the Earth’s deformation patterns. However, the forward and inverse modelling of mechanical anisotropy in 3D large-scale domains has been traditionally hampered by the intensive computational cost and the lack of a dedicated, open-source computational framework. Here we introduce ECOMAN, a software package for modelling strain-/stress-induced rock fabrics and testing the effects of the resulting elastic and viscous anisotropy on seismic imaging and mantle convection patterns. Differently from existing analogous software, the modelling of strain-induced fabrics has been extended to all mantle levels and it has been optimised to run across multiple CPUs, yielding strong scaling efficiency. In addition, shape preferred orientation (SPO)-related structures can be modelled and superimposed over lattice/crystallographic preferred orientation (LPO/CPO) fabrics, which allows the consideration of the mechanical effects of fluid-filled cracks, foliated/lineated grain-scale fabrics and rock-scale layering. One of the most important innovations is the Platform for Seismic Imaging (PSI), a set of programs for performing forward and inverse seismic modelling in isotropic/anisotropic media using real or synthetic seismic datasets. The anisotropic inversion strategy is capable of recovering parameters describing a tilted transversely isotropic (TTI) medium, which is required to reconstruct 3D structures and mantle strain patterns and to validate geodynamic models.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"32 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769860","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}
Mengdan Chen, Changxin Yin, Danling Chen, Long Tian, Liang Liu, Lei Kang
Abstract. Water dissolved in nominally anhydrous minerals (NAMs) can be transported to deep regions of the Earth through subducting slabs, thereby significantly influencing the physicochemical properties of deep-Earth materials and impacting dynamic processes in the deep Earth. Stishovite, a prominent mineral present in subducting slabs, remains stable at mantle pressures of 9–50 GPa and can incorporate various amounts of water (H+, OH−, and H2O) in its crystal structure. Consequently, stishovite can play a crucial role in transporting water into the deep Earth through subducting slabs. This paper provides a comprehensive review of the research process concerning water (hydrogen) solubility in stishovite. The key factors that govern water solubility in stishovite are summarized as temperature, pressure, water fugacity, and aluminum content. Combined with published results on the dependence of water solubility on the aforementioned parameters, this paper proposes a new equation to describe the solubility of water in Al-bearing stishovite. Calculation results based on this equation suggest that stishovite may effectively accommodate water released from processes such as hydrous mineral breakdown, which could ultimately contribute to the presence of a water-rich transition zone.
{"title":"Hydrogen solubility of stishovite provides insights into water transportation to the deep Earth","authors":"Mengdan Chen, Changxin Yin, Danling Chen, Long Tian, Liang Liu, Lei Kang","doi":"10.5194/se-15-215-2024","DOIUrl":"https://doi.org/10.5194/se-15-215-2024","url":null,"abstract":"Abstract. Water dissolved in nominally anhydrous minerals (NAMs) can be transported to deep regions of the Earth through subducting slabs, thereby significantly influencing the physicochemical properties of deep-Earth materials and impacting dynamic processes in the deep Earth. Stishovite, a prominent mineral present in subducting slabs, remains stable at mantle pressures of 9–50 GPa and can incorporate various amounts of water (H+, OH−, and H2O) in its crystal structure. Consequently, stishovite can play a crucial role in transporting water into the deep Earth through subducting slabs. This paper provides a comprehensive review of the research process concerning water (hydrogen) solubility in stishovite. The key factors that govern water solubility in stishovite are summarized as temperature, pressure, water fugacity, and aluminum content. Combined with published results on the dependence of water solubility on the aforementioned parameters, this paper proposes a new equation to describe the solubility of water in Al-bearing stishovite. Calculation results based on this equation suggest that stishovite may effectively accommodate water released from processes such as hydrous mineral breakdown, which could ultimately contribute to the presence of a water-rich transition zone.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"36 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769856","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}
Wei Li, Megha Chakraborty, Jonas Köhler, Claudia Quinteros-Cartaya, Georg Rümpker, Nishtha Srivastava
Abstract. Seismic phase picking and magnitude estimation are fundamental aspects of earthquake monitoring and seismic event analysis. Accurate phase picking allows for precise characterization of seismic wave arrivals, contributing to a better understanding of earthquake events. Likewise, accurate magnitude estimation provides crucial information about an earthquake's size and potential impact. Together, these components enhance our ability to monitor seismic activity effectively. In this study, we explore the application of deep-learning techniques for earthquake detection and magnitude estimation using continuous seismic recordings. Our approach introduces DynaPicker, which leverages dynamic convolutional neural networks to detect seismic body-wave phases in continuous seismic data. We demonstrate the effectiveness of DynaPicker using various open-source seismic datasets, including both window-format and continuous recordings. We evaluate its performance in seismic phase identification and arrival-time picking, as well as its robustness in classifying seismic phases using low-magnitude seismic data in the presence of noise. Furthermore, we integrate the phase arrival-time information into a previously published deep-learning model for magnitude estimation. We apply this workflow to continuous recordings of aftershock sequences following the Turkey earthquake. The results of this case study showcase the reliability of our approach in earthquake detection, phase picking, and magnitude estimation, contributing valuable insights to seismic event analysis.
{"title":"Earthquake monitoring using deep learning with a case study of the Kahramanmaras Turkey earthquake aftershock sequence","authors":"Wei Li, Megha Chakraborty, Jonas Köhler, Claudia Quinteros-Cartaya, Georg Rümpker, Nishtha Srivastava","doi":"10.5194/se-15-197-2024","DOIUrl":"https://doi.org/10.5194/se-15-197-2024","url":null,"abstract":"Abstract. Seismic phase picking and magnitude estimation are fundamental aspects of earthquake monitoring and seismic event analysis. Accurate phase picking allows for precise characterization of seismic wave arrivals, contributing to a better understanding of earthquake events. Likewise, accurate magnitude estimation provides crucial information about an earthquake's size and potential impact. Together, these components enhance our ability to monitor seismic activity effectively. In this study, we explore the application of deep-learning techniques for earthquake detection and magnitude estimation using continuous seismic recordings. Our approach introduces DynaPicker, which leverages dynamic convolutional neural networks to detect seismic body-wave phases in continuous seismic data. We demonstrate the effectiveness of DynaPicker using various open-source seismic datasets, including both window-format and continuous recordings. We evaluate its performance in seismic phase identification and arrival-time picking, as well as its robustness in classifying seismic phases using low-magnitude seismic data in the presence of noise. Furthermore, we integrate the phase arrival-time information into a previously published deep-learning model for magnitude estimation. We apply this workflow to continuous recordings of aftershock sequences following the Turkey earthquake. The results of this case study showcase the reliability of our approach in earthquake detection, phase picking, and magnitude estimation, contributing valuable insights to seismic event analysis.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"23 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769850","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}
Abstract. Petit-spot volcanoes, occurring due to plate flexure, have been reported globally. As the petit-spot melts ascend from the asthenosphere, they provide crucial information of the lithosphere–asthenosphere boundary. Herein, we examined the lava outcrops of six monogenetic volcanoes formed by petit-spot volcanism in the western Pacific. We then analyzed the 40Ar/39Ar ages, major and trace element compositions, and Sr, Nd, and Pb isotopic ratios of the petit-spot basalts. The 40Ar/39Ar ages of two monogenetic volcanoes were ca. 2.6 Ma (million years ago) and ca. 0 Ma. The isotopic compositions of the western Pacific petit-spot basalts suggest geochemically similar melting sources. They were likely derived from a mixture of high-μ (HIMU) mantle-like and enriched mantle (EM)-1-like components related to carbonatitic/carbonated materials and recycled crustal components. The characteristic trace element composition (i.e., Zr, Hf, and Ti depletions) of the western Pacific petit-spot magmas could be explained by the partial melting of ∼ 5 % crust bearing garnet lherzolite, with 10 % carbonatite flux to a given mass of the source, as implied by a mass-balance-based melting model. This result confirms the involvement of carbonatite melt and recycled crust in the source of petit-spot melts. It provides insights into the genesis of tectonic-induced volcanoes, including the Hawaiian North Arch and Samoan petit-spot-like rejuvenated volcanoes that have a similar trace element composition to petit-spot basalts.
{"title":"Contribution of carbonatite and recycled oceanic crust to petit-spot lavas on the western Pacific Plate","authors":"Kazuto Mikuni, Naoto Hirano, Shiki Machida, Hirochika Sumino, Norikatsu Akizawa, Akihiro Tamura, Tomoaki Morishita, Yasuhiro Kato","doi":"10.5194/se-15-167-2024","DOIUrl":"https://doi.org/10.5194/se-15-167-2024","url":null,"abstract":"Abstract. Petit-spot volcanoes, occurring due to plate flexure, have been reported globally. As the petit-spot melts ascend from the asthenosphere, they provide crucial information of the lithosphere–asthenosphere boundary. Herein, we examined the lava outcrops of six monogenetic volcanoes formed by petit-spot volcanism in the western Pacific. We then analyzed the 40Ar/39Ar ages, major and trace element compositions, and Sr, Nd, and Pb isotopic ratios of the petit-spot basalts. The 40Ar/39Ar ages of two monogenetic volcanoes were ca. 2.6 Ma (million years ago) and ca. 0 Ma. The isotopic compositions of the western Pacific petit-spot basalts suggest geochemically similar melting sources. They were likely derived from a mixture of high-μ (HIMU) mantle-like and enriched mantle (EM)-1-like components related to carbonatitic/carbonated materials and recycled crustal components. The characteristic trace element composition (i.e., Zr, Hf, and Ti depletions) of the western Pacific petit-spot magmas could be explained by the partial melting of ∼ 5 % crust bearing garnet lherzolite, with 10 % carbonatite flux to a given mass of the source, as implied by a mass-balance-based melting model. This result confirms the involvement of carbonatite melt and recycled crust in the source of petit-spot melts. It provides insights into the genesis of tectonic-induced volcanoes, including the Hawaiian North Arch and Samoan petit-spot-like rejuvenated volcanoes that have a similar trace element composition to petit-spot basalts.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"16 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769982","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}
Pub Date : 2024-02-08DOI: 10.5194/egusphere-2024-308
Eszter Békési, Jan-Diederik van Wees, Kristóf Porkoláb, Mátyás Hencz, Márta Berkesi
Abstract. The reconstruction of thermal evolution in sedimentary basins is a key input for constraining geodynamic processes and geo-energy resource potential. We present a methodology to reproduce the most important transient thermal footprints accompanying basin formation: lithosphere extension and sedimentation. The forward model is extended with data assimilation to constrain models with temperature measurements. We apply the methodology to the NW part of Hungary. Realistic past- and present-day temperature predictions for the entire lithosphere are achieved, suggesting the relatively uniform, but strong attenuation of the mantle lithosphere through extension, and relatively small variations in the present-day thermal lithosphere thickness. The new temperature model allows an improved estimation of lithosphere rheology and the interpretation of mantle xenolith origins.
{"title":"Modelling transient thermal processes in the lithosphere: application to the NW Pannonian basin","authors":"Eszter Békési, Jan-Diederik van Wees, Kristóf Porkoláb, Mátyás Hencz, Márta Berkesi","doi":"10.5194/egusphere-2024-308","DOIUrl":"https://doi.org/10.5194/egusphere-2024-308","url":null,"abstract":"<strong>Abstract.</strong> The reconstruction of thermal evolution in sedimentary basins is a key input for constraining geodynamic processes and geo-energy resource potential. We present a methodology to reproduce the most important transient thermal footprints accompanying basin formation: lithosphere extension and sedimentation. The forward model is extended with data assimilation to constrain models with temperature measurements. We apply the methodology to the NW part of Hungary. Realistic past- and present-day temperature predictions for the entire lithosphere are achieved, suggesting the relatively uniform, but strong attenuation of the mantle lithosphere through extension, and relatively small variations in the present-day thermal lithosphere thickness. The new temperature model allows an improved estimation of lithosphere rheology and the interpretation of mantle xenolith origins.","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"8 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769985","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}
Yukinojo Koyama, Simon R. Wallis, Takayoshi Nagaya
Abstract. Maximum shear stress along an active deformation zone marking the subduction plate interface is important for understanding earthquake phenomena and is an important input parameter in subduction zone thermomechanical modeling. However, such maximum shear stress is difficult to measure directly at depths more than a few kilometers and is generally estimated by simulation using a range of input parameters with large associated uncertainties. In addition, estimated values generally represent maximum shear stress conditions over short observation timescales, which may not be directly applicable to long-timescale subduction zone modeling. Rocks originally located deep in subduction zones can record information about deformation processes, including maximum shear stress conditions, occurring in regions that cannot be directly accessed. The estimated maximum shear stress is likely to be representative of maximum shear stress experienced over geological timescales and be suitable to use in subduction zone modeling over timescales of millions to tens of millions of years. In this study, we estimated maximum shear stress along a subduction plate interface by using samples from the Sanbagawa metamorphic belt of southwestern (SW) Japan, in which slivers of mantle-wedge-derived serpentinite are widely distributed and in direct contact with metasedimentary rocks derived from the subducted oceanic plate. These areas can be related to the zone of active deformation along the subduction plate interface. To obtain estimates of maximum shear stress at the subduction interface, we focused on the microstructure of quartz-rich metamorphic rocks – quartz is the main component of the rocks we collected and its deformation stress is assumed to be roughly representative of the stress experienced by the surrounding rock and plate interface deformation zone. Maximum shear stress was calculated by applying deformation temperatures estimated by the crystallographic orientation of quartz (the quartz c-axis fabric opening-angle thermometer) and the apparent grain size of dynamically recrystallized quartz in a thin section to an appropriate piezometer. Combined with information on sample deformation depth, estimated from the P–T (pressure–temperature) path and deformation temperatures, it is suggested that there was nearly constant maximum shear stress of 15–41 MPa in the depth range of about 15–30 km, assuming plane stress conditions even when uncertainties related to the measurement direction of thin section and piezometer differences are included. The Sanbagawa belt formed in a warm subduction zone. Deep slow earthquakes are commonly observed in modern-day warm subduction zones such as SW Japan, which has a similar thermal structure to the Sanbagawa belt. In addition, deep slow earthquakes are commonly observed to be concentrated in a domain under the shallow part of the mantle wedge. Samples showed the depth conditions near the mantle wedge, suggesting that these s
摘要沿俯冲板块界面活动变形带的最大剪应力对于理解地震现象非常重要，也是俯冲带热力学建模的重要输入参数。然而，这种最大剪应力在深度超过几千米的地方很难直接测量，通常是通过使用一系列相关不确定性很大的输入参数进行模拟估算。此外，估算值通常代表短观测时间尺度内的最大剪应力状况，可能无法直接用于长时间尺度的俯冲带建模。原本位于俯冲带深处的岩石可以记录发生在无法直接进入区域的变形过程信息，包括最大剪应力条件。估算出的最大剪应力可能代表地质时间尺度上经历的最大剪应力，适合用于时间尺度为数百万年至数千万年的俯冲带建模。在这项研究中，我们利用日本西南部Sanbagawa变质岩带的样本估算了俯冲板块界面的最大剪应力，该变质岩带广泛分布着源自地幔楔的蛇纹岩，并与源自俯冲大洋板块的变质岩直接接触。这些地区与俯冲板块界面的活动变形区有关。为了估算俯冲界面的最大剪应力，我们重点研究了富含石英的变质岩的微观结构--石英是我们所采集岩石的主要成分，其变形应力被假定为大致代表了周围岩石和板块界面变形区所经历的应力。最大剪切应力的计算方法是将根据石英晶体学取向估算的变形温度（石英 c 轴织物开角温度计）和薄片中动态再结晶石英的表观晶粒尺寸应用到适当的压强计中。结合根据 P-T（压力-温度）路径和变形温度估算出的样品变形深度信息，即使考虑到与薄片测量方向和压强计差异有关的不确定性，假定在平面应力条件下，在约 15-30 千米的深度范围内也存在 15-41 兆帕的几乎恒定的最大剪应力。山巴格瓦带形成于温暖的俯冲带。在现代的暖俯冲带（如日本西南部）经常观测到深慢速地震，其热结构与桑巴川带类似。此外，深缓震通常集中在地幔楔浅层下的一个区域。样本显示了地幔楔附近的深度条件，表明这些样本是在具有类似于深缓震域特征的区域形成的。估算的最大剪应力不仅可用于长尺度俯冲带建模，还代表了同一区域慢地震成核的初始条件。
{"title":"Subduction plate interface shear stress associated with rapid subduction at deep slow earthquake depths: example from the Sanbagawa belt, southwestern Japan","authors":"Yukinojo Koyama, Simon R. Wallis, Takayoshi Nagaya","doi":"10.5194/se-15-143-2024","DOIUrl":"https://doi.org/10.5194/se-15-143-2024","url":null,"abstract":"Abstract. Maximum shear stress along an active deformation zone marking the subduction plate interface is important for understanding earthquake phenomena and is an important input parameter in subduction zone thermomechanical modeling. However, such maximum shear stress is difficult to measure directly at depths more than a few kilometers and is generally estimated by simulation using a range of input parameters with large associated uncertainties. In addition, estimated values generally represent maximum shear stress conditions over short observation timescales, which may not be directly applicable to long-timescale subduction zone modeling. Rocks originally located deep in subduction zones can record information about deformation processes, including maximum shear stress conditions, occurring in regions that cannot be directly accessed. The estimated maximum shear stress is likely to be representative of maximum shear stress experienced over geological timescales and be suitable to use in subduction zone modeling over timescales of millions to tens of millions of years. In this study, we estimated maximum shear stress along a subduction plate interface by using samples from the Sanbagawa metamorphic belt of southwestern (SW) Japan, in which slivers of mantle-wedge-derived serpentinite are widely distributed and in direct contact with metasedimentary rocks derived from the subducted oceanic plate. These areas can be related to the zone of active deformation along the subduction plate interface. To obtain estimates of maximum shear stress at the subduction interface, we focused on the microstructure of quartz-rich metamorphic rocks – quartz is the main component of the rocks we collected and its deformation stress is assumed to be roughly representative of the stress experienced by the surrounding rock and plate interface deformation zone. Maximum shear stress was calculated by applying deformation temperatures estimated by the crystallographic orientation of quartz (the quartz c-axis fabric opening-angle thermometer) and the apparent grain size of dynamically recrystallized quartz in a thin section to an appropriate piezometer. Combined with information on sample deformation depth, estimated from the P–T (pressure–temperature) path and deformation temperatures, it is suggested that there was nearly constant maximum shear stress of 15–41 MPa in the depth range of about 15–30 km, assuming plane stress conditions even when uncertainties related to the measurement direction of thin section and piezometer differences are included. The Sanbagawa belt formed in a warm subduction zone. Deep slow earthquakes are commonly observed in modern-day warm subduction zones such as SW Japan, which has a similar thermal structure to the Sanbagawa belt. In addition, deep slow earthquakes are commonly observed to be concentrated in a domain under the shallow part of the mantle wedge. Samples showed the depth conditions near the mantle wedge, suggesting that these s","PeriodicalId":21912,"journal":{"name":"Solid Earth","volume":"35 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139770363","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}
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