Physics of the Earth and Planetary Interiors最新文献

Thermal and magnetic evolution of an Earth-like planet with a basal magma ocean 具有基底岩浆海洋的类地行星的热演化和磁演化

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-10-09 DOI: 10.1016/j.pepi.2024.107267

Earth's geodynamo has operated for over 3.5 billion years. The magnetic field is currently powered by thermocompositional convection in the outer core, which involves the release of light elements and latent heat as the inner core solidifies. However, since the inner core nucleated no more than 1.5 billion years ago, the early dynamo could not rely on these buoyancy sources. Given recent estimates of the thermal conductivity of the outer core, an alternative mechanism may be required to sustain the geodynamo prior to nucleation of the inner core. One possibility is a silicate dynamo operating in a long-lived basal magma ocean. Here, we investigate the structural, thermal, buoyancy, and magnetic evolution of an Earth-like terrestrial planet. Using modern equations of state and melting curves, we include a time-dependent parameterization of the compositional evolution of an iron-rich basal magma ocean. We combine an internal structure integration of the planet with energy budgets in a coupled core, basal magma ocean, and mantle system. We determine the thermocompositional convective stability of the core and the basal magma ocean, and assess their respective dynamo activity using entropy budgets and magnetic Reynolds numbers. Our conservative nominal model predicts a transient basal magma ocean dynamo followed by a core dynamo after 1 billion years. The model is sensitive to several parameters, including the initial temperature of the core-mantle boundary, the parameterization of mantle convection, the composition of the basal magma ocean, the radiogenic content of the planet, as well as convective velocity and magnetic scaling laws. We use the nominal model to constrain the range of basal magma ocean electrical conductivity and core thermal conductivity that sustain a dynamo. This highlights the importance of constraining the parameters and transport properties that influence planetary evolution using experiments and simulations conducted at pressure, temperature, and composition conditions found in planetary interior, in order to reduce model degeneracies.

地球的地球动力已经运行了 35 亿多年。磁场目前由外核的热合成对流提供动力，这涉及内核凝固时轻元素和潜热的释放。然而，由于内核成核的时间不超过 15 亿年，早期的发电机不可能依靠这些浮力源。鉴于最近对外核热导率的估计，可能需要一种替代机制来维持内核成核前的地球动力。一种可能是在长寿命基底岩浆海洋中运行的硅酸盐动力。在这里，我们研究了类地行星的结构、热、浮力和磁力演化。利用现代状态方程和熔融曲线，我们对富含铁的基底岩浆洋的成分演变进行了随时间变化的参数化。我们将行星的内部结构整合与耦合内核、基底岩浆海洋和地幔系统的能量预算结合起来。我们确定了地核和基底岩浆洋的热合成对流稳定性，并利用熵预算和磁雷诺数评估了它们各自的动力活动。我们保守的名义模型预测，在 10 亿年后，地核动力将产生瞬时的基底岩浆洋动力。该模型对几个参数很敏感，包括地核-地幔边界的初始温度、地幔对流的参数化、基底岩浆洋的成分、行星的放射性含量以及对流速度和磁力缩放定律。我们利用名义模型来约束维持动力机的基底岩浆洋导电率和核心热传导率的范围。这凸显了利用在行星内部发现的压力、温度和成分条件下进行的实验和模拟来约束影响行星演化的参数和传输特性以减少模型退化的重要性。

{"title":"Thermal and magnetic evolution of an Earth-like planet with a basal magma ocean","authors":"","doi":"10.1016/j.pepi.2024.107267","DOIUrl":"10.1016/j.pepi.2024.107267","url":null,"abstract":"<div><div>Earth's geodynamo has operated for over 3.5 billion years. The magnetic field is currently powered by thermocompositional convection in the outer core, which involves the release of light elements and latent heat as the inner core solidifies. However, since the inner core nucleated no more than 1.5 billion years ago, the early dynamo could not rely on these buoyancy sources. Given recent estimates of the thermal conductivity of the outer core, an alternative mechanism may be required to sustain the geodynamo prior to nucleation of the inner core. One possibility is a silicate dynamo operating in a long-lived basal magma ocean. Here, we investigate the structural, thermal, buoyancy, and magnetic evolution of an Earth-like terrestrial planet. Using modern equations of state and melting curves, we include a time-dependent parameterization of the compositional evolution of an iron-rich basal magma ocean. We combine an internal structure integration of the planet with energy budgets in a coupled core, basal magma ocean, and mantle system. We determine the thermocompositional convective stability of the core and the basal magma ocean, and assess their respective dynamo activity using entropy budgets and magnetic Reynolds numbers. Our conservative nominal model predicts a transient basal magma ocean dynamo followed by a core dynamo after 1 billion years. The model is sensitive to several parameters, including the initial temperature of the core-mantle boundary, the parameterization of mantle convection, the composition of the basal magma ocean, the radiogenic content of the planet, as well as convective velocity and magnetic scaling laws. We use the nominal model to constrain the range of basal magma ocean electrical conductivity and core thermal conductivity that sustain a dynamo. This highlights the importance of constraining the parameters and transport properties that influence planetary evolution using experiments and simulations conducted at pressure, temperature, and composition conditions found in planetary interior, in order to reduce model degeneracies.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

3-D P-wave velocity structure of the upper mantle beneath eastern Indonesia from body wave tomography 通过体波层析成像研究印度尼西亚东部地下上地幔的三维 P 波速度结构

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-10-02 DOI: 10.1016/j.pepi.2024.107266

Eastern Indonesia's tectonic setting is well known for its complexity and intense seismic activity. Controlled by several major and minor plates, including the Eurasian, Australian, and Pacific plates, this region is famous for its U-shaped subduction system beneath the Banda Arc. To better understand the architecture of the underlying structure in this region, we performed body-wave travel time tomography using ten years of catalog data provided by the Indonesian Agency for Meteorology, Climatology, and Geophysics. We utilize 9729 events in total, from which 46,446 P-wave arrival times were extracted. We used a double difference method to relocate the initial event catalog, which produced a pattern of seismicity consistent with a curved subduction system. Our tomographic model reveals a high velocity band between 90 and 240 km depth in the upper mantle, which is interpreted to be a concave dipping lithospheric slab that is parallel to the present-day Banda arc. Our results also show that lithosphere subducting from the north and south starts to collide at a depth of 300–350 km and becomes shallower further east. Apparent discontinuities in the high velocity band and a corresponding lack of seismicity supports the presence of a slab tear to the west of Seram. A dipping high velocity structure that is present from south to north beneath the island of Timor represents a subducting slab that dips more steeply beyond a depth of 150–200 km, which appears consistent with slab roll-back. Our tomographic model also shows evidence of back arc thrusting to the north of Sumbawa and Flores Islands in the form of a south-dipping higher velocity band at shallow depth. Furthermore, our tomographic models also reveal the possible presence of underthrust continental forearc in the form of a thin higher velocity anomaly that connects the backarc thrust and northward dipping lithosphere slab in the Timor area. Finally, a zone of low velocity above the higher velocity slab is clearly seen beneath Seram Island at a depth of ∼100 km and may represent a partial melting zone.

印度尼西亚东部的构造环境以其复杂性和强烈的地震活动而闻名。该地区受欧亚板块、澳大利亚板块和太平洋板块等几大板块和次板块的控制，以班达弧下的 U 型俯冲系统而闻名。为了更好地了解该地区的底层结构，我们利用印度尼西亚气象、气候和地球物理局提供的十年目录数据进行了体波走时层析成像。我们总共利用了 9729 个事件，从中提取了 46446 个 P 波到达时间。我们使用双差分法重新定位初始事件目录，从而得出与弯曲俯冲系统相一致的地震模式。我们的层析成像模型揭示了上地幔 90 至 240 千米深处的高速带，该高速带被解释为与现今班达弧平行的凹倾岩石圈板块。我们的研究结果还表明，从北面和南面俯冲而来的岩石圈在 300-350 千米深处开始碰撞，越往东越浅。高速带的明显不连续性和相应的地震活动的缺失，支持了塞拉姆以西板块撕裂的存在。帝汶岛下方自南向北存在一个倾斜的高速结构，它代表了俯冲板块，在深度超过 150-200 千米后，倾斜度更大，这似乎与板块回滚一致。我们的层析成像模型还显示，在松巴哇岛和弗洛勒斯岛以北，有背弧推力的迹象，其形式是在浅层有一个向南倾斜的较高速度带。此外，我们的层析成像模型还揭示了可能存在的大陆前弧下推，其形式为一条较细的高速异常带，连接着帝汶地区的后弧推力和北倾岩石圈板块。最后，在塞拉姆岛下方 100 千米深处，可以清楚地看到高速板块上方的低速区，可能代表部分熔化区。

{"title":"3-D P-wave velocity structure of the upper mantle beneath eastern Indonesia from body wave tomography","authors":"","doi":"10.1016/j.pepi.2024.107266","DOIUrl":"10.1016/j.pepi.2024.107266","url":null,"abstract":"<div><div>Eastern Indonesia's tectonic setting is well known for its complexity and intense seismic activity. Controlled by several major and minor plates, including the Eurasian, Australian, and Pacific plates, this region is famous for its U-shaped subduction system beneath the Banda Arc. To better understand the architecture of the underlying structure in this region, we performed body-wave travel time tomography using ten years of catalog data provided by the Indonesian Agency for Meteorology, Climatology, and Geophysics. We utilize 9729 events in total, from which 46,446 P-wave arrival times were extracted. We used a double difference method to relocate the initial event catalog, which produced a pattern of seismicity consistent with a curved subduction system. Our tomographic model reveals a high velocity band between 90 and 240 km depth in the upper mantle, which is interpreted to be a concave dipping lithospheric slab that is parallel to the present-day Banda arc. Our results also show that lithosphere subducting from the north and south starts to collide at a depth of 300–350 km and becomes shallower further east. Apparent discontinuities in the high velocity band and a corresponding lack of seismicity supports the presence of a slab tear to the west of Seram. A dipping high velocity structure that is present from south to north beneath the island of Timor represents a subducting slab that dips more steeply beyond a depth of 150–200 km, which appears consistent with slab roll-back. Our tomographic model also shows evidence of back arc thrusting to the north of Sumbawa and Flores Islands in the form of a south-dipping higher velocity band at shallow depth. Furthermore, our tomographic models also reveal the possible presence of underthrust continental forearc in the form of a thin higher velocity anomaly that connects the backarc thrust and northward dipping lithosphere slab in the Timor area. Finally, a zone of low velocity above the higher velocity slab is clearly seen beneath Seram Island at a depth of ∼100 km and may represent a partial melting zone.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Reinvestigating the Dufek Intrusion, through joint gravity and magnetic models 通过重力和磁力联合模型重新研究杜菲克侵入区

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-10-02 DOI: 10.1016/j.pepi.2024.107268

The Dufek layered mafic intrusion represents the only exposed, deep-seated, part of the Ferrar Large Igneous Province, which extends >3500 km across Antarctica and into parts of Tasmania and New Zealand. The Dufek Intrusion is in a key position at the boundary between the Jurassic Weddell Sea Rift System and the East Antarctic Craton. It may have been a conduit for some of the Ferrar magmas, or a deep-seated equivalent to the shallower sills seen in other sectors of Antarctica. Although a significant intrusion, equivalent at least to the Stillwater complex in the USA, its true scale and geometry, along with the relative timing of emplacement is disputed. We present new 3D models of gravity and magnetic data which constrain the geometry of the intrusion, show how separate lobes of the intrusion are linked and identify a possible extension of the intrusion to the east. We also discuss the implications for how the intrusion may have been emplaced.

杜菲克层状岩浆侵入体是费拉尔大火成岩带唯一暴露的深层部分，该熔岩带横跨南极洲，延伸至塔斯马尼亚和新西兰部分地区，全长3500千米。杜菲克侵入体位于侏罗纪威德尔海裂谷系统和南极东部克拉通之间边界的关键位置。它可能是一些费拉尔岩浆的导管，也可能是南极洲其他地区较浅火山岩的深层侵入体。虽然这是一个重要的侵入体，至少相当于美国的 Stillwater 复合体，但其真实规模和几何形状以及相对的形成时间还存在争议。我们介绍了新的重力和磁力数据三维模型，这些数据限制了侵入体的几何形状，显示了侵入体的独立裂片是如何联系在一起的，并确定了侵入体向东延伸的可能性。我们还讨论了侵入体如何形成的影响。

引用次数: 0

The sensitivity of lowermost mantle anisotropy to past mantle convection 最下地幔各向异性对过去地幔对流的敏感性

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-09-24 DOI: 10.1016/j.pepi.2024.107264

It is widely believed that seismic anisotropy in the lowermost mantle is caused by the flow-induced alignment of anisotropic crystals such as post-perovskite. What is unclear, however, is whether the anisotropy observations in the lowermost mantle hold information about past mantle flow, or if they only inform us about the present-day flow field. To investigate this, we compare the general and seismic anisotropy calculated using Earth-like mantle convection models where one has a time-varying flow, and another where the present-day flow is constant throughout time. To do this, we track a post-perovskite polycrystal through the flow fields and calculate texture development using the sampled strain rate and the visco-plastic self-consistent approach. We assume dominant slip on (001) and test the effect of the relative importance of this glide plane over others by using three different plasticity models with different efficiencies at developing texture. We compare the radial anisotropy parameters and the anisotropic components of the elastic tensors produced by the flow field test cases at the same location. We find, under all ease-of-texturing cases, the radial anisotropy is very similar (difference

< 2 %

) in the majority of locations and in some regions, the difference can be very large (

> 10 %

). The same is true when comparing the elastic tensors directly. Varying the ease-of-texture development in the crystal aggregate suggests that easier-to-texture material may hold a stronger signal from past flow than harder-to-texture material. Our results imply that broad-scale observations of seismic anisotropy such as those from seismic tomography, 1-D estimates and normal mode observations, will be mainly sensitive to present-day flow. Shear-wave splitting measurements, however, could hold information about past mantle flow. In general, mantle memory expressed in anisotropy may be dependent on path length in the post-perovskite stability field. Our work implies that, as knowledge of the exact causative mechanism of lowermost mantle anisotropy develops, we may be able to constrain both present-day and past mantle convection.

人们普遍认为，最下地幔的地震各向异性是由流动引起的各向异性晶体（如后辉石）排列造成的。然而，目前尚不清楚的是，在最下地幔中观测到的各向异性是否包含了有关过去地幔流动的信息，或者说，它们是否只为我们提供了有关现今流动场的信息。为了研究这个问题，我们比较了使用类地幔对流模型计算出的一般各向异性和地震各向异性，其中一个模型的流动是随时间变化的，而另一个模型的现今流动在整个时间内是恒定的。为此，我们在流场中跟踪了后透辉石多晶体，并使用采样应变率和粘弹性自洽方法计算了纹理的发展。我们假定 (001) 上存在主要滑移，并使用三种不同的塑性模型来测试该滑移面相对于其他滑移面的相对重要性，这些模型在纹理发展方面具有不同的效率。我们比较了径向各向异性参数和同一位置流场测试案例产生的弹性张量的各向异性分量。我们发现，在所有易于形成纹理的情况下，大多数位置的径向各向异性非常相似（差异为 2%），而在某些区域，差异可能非常大（10%）。直接比较弹性张量也是如此。晶体集合体中纹理发展的难易程度不同，表明纹理较易发展的物质可能比纹理较难发展的物质从过去的流动中获得更强的信号。我们的结果表明，对地震各向异性的大尺度观测，如地震层析成像、一维估算和法模观测，将主要对现今的流动敏感。然而，剪切波分裂测量可能包含有关过去地幔流动的信息。一般来说，以各向异性表示的地幔记忆可能取决于后围岩稳定场的路径长度。我们的工作意味着，随着对最下层地幔各向异性确切成因机制的了解，我们可能能够对现今和过去的地幔对流进行约束。

{"title":"The sensitivity of lowermost mantle anisotropy to past mantle convection","authors":"","doi":"10.1016/j.pepi.2024.107264","DOIUrl":"10.1016/j.pepi.2024.107264","url":null,"abstract":"<div><div>It is widely believed that seismic anisotropy in the lowermost mantle is caused by the flow-induced alignment of anisotropic crystals such as post-perovskite. What is unclear, however, is whether the anisotropy observations in the lowermost mantle hold information about past mantle flow, or if they only inform us about the present-day flow field. To investigate this, we compare the general and seismic anisotropy calculated using Earth-like mantle convection models where one has a time-varying flow, and another where the present-day flow is constant throughout time. To do this, we track a post-perovskite polycrystal through the flow fields and calculate texture development using the sampled strain rate and the visco-plastic self-consistent approach. We assume dominant slip on (001) and test the effect of the relative importance of this glide plane over others by using three different plasticity models with different efficiencies at developing texture. We compare the radial anisotropy parameters and the anisotropic components of the elastic tensors produced by the flow field test cases at the same location. We find, under all ease-of-texturing cases, the radial anisotropy is very similar (difference <span><math><mo><</mo><mn>2</mn><mo>%</mo></math></span>) in the majority of locations and in some regions, the difference can be very large (<span><math><mo>></mo><mn>10</mn><mo>%</mo></math></span>). The same is true when comparing the elastic tensors directly. Varying the ease-of-texture development in the crystal aggregate suggests that easier-to-texture material may hold a stronger signal from past flow than harder-to-texture material. Our results imply that broad-scale observations of seismic anisotropy such as those from seismic tomography, 1-D estimates and normal mode observations, will be mainly sensitive to present-day flow. Shear-wave splitting measurements, however, could hold information about past mantle flow. In general, mantle memory expressed in anisotropy may be dependent on path length in the post-perovskite stability field. Our work implies that, as knowledge of the exact causative mechanism of lowermost mantle anisotropy develops, we may be able to constrain both present-day and past mantle convection.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142328310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Shock-induced phase transitions in siderite up to 90 GPa and implications for deep carbon cycle 高达 90 GPa 的菱铁矿中冲击诱导的相变及其对深层碳循环的影响

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-09-21 DOI: 10.1016/j.pepi.2024.107265

The phase stability of carbonates under mantle conditions is important for understanding the global carbon cycle. In this study, the Hugoniot data of a natural siderite (FeCO₃) were measured up to 90 GPa using the plane-plate impact method. Two successive phase transitions were observed at 38–40 GPa and 65–69 GPa, respectively. In comparison with the static compression results, the first phase transition was identified as a spin transition, and the second is attributed to the self-redox reaction. The volume change during the self-redox transition is consistent with the reaction products of tetrairon orthocarbonate Fe₄C₃O₁₂ and diamond. Using the measured Hugoniot data, we estimated the density of Fe₄C₃O₁₂ along the lower mantle conditions and found it to be higher than the seismic values. Our results suggest siderite plays an important role in the deep carbon cycle.

地幔条件下碳酸盐的相稳定性对于了解全球碳循环非常重要。在这项研究中，使用平面冲击法测量了天然菱铁矿（FeCO3）最高达 90 GPa 的休格尼奥特数据。在 38-40 GPa 和 65-69 GPa 处分别观察到两个连续的相变。与静态压缩结果相比，第一个相变被确定为自旋转变，第二个相变则归因于自氧化还原反应。自氧化还原转变过程中的体积变化与正碳酸四铁 Fe4C3O12 和金刚石的反应产物一致。利用测得的胡戈尼奥特数据，我们估算了沿下地幔条件的 Fe4C3O12 密度，发现它高于地震值。我们的研究结果表明，菱铁矿在深部碳循环中发挥着重要作用。

引用次数: 0

A potential deep geothermal reservoir in eastern Ladakh as inferred from the upper crustal geoelectric structure of the region 从拉达克地区上地壳地电结构推断出该地区东部潜在的深层地热储层

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-09-20 DOI: 10.1016/j.pepi.2024.107263

The Ladakh Himalaya is a repository of the evolutionary history of the India-Eurasia convergent plate margin. We present the results of a magnetotelluric (MT) study carried out in Eastern Ladakh along a 40-km-long profile traversing across various tectonic domains of this plate margin. We modeled the MT dataset by two-dimensional (2-D) and three-dimensional (3-D) inversion algorithms. The upper crustal geoelectric model obtained by 2-D inversion of distortion corrected and decomposed data of 18 sites shows an excellent match with the surface geology. In this model, the Indus Suture Zone (ISZ) appears as a steeply dipping contact and the Ladakh batholith is about 10 to 12 km thick. The model yields a prominent electrical conductor of ∼6 km diameter at 4 km depth beneath the Tso Morari Crystallines with an offshoot of a small conductor that rises upward along the ISZ. The geoelectrical model obtained by 3-D inversion is broadly consistent with the 2-D model but also reveals off-profile features and a connectivity of the shallow conductors with a widespread conductive zone at deeper level of the upper crust. In view of the presence of Puga and Chumathang hot springs towards west and Demchok hot springs towards east of our study region, we infer these conductors to be representing a potential major geothermal reservoir system connected to the widespread deeper conductive zone of partial melts, which extends from the southern Tibet to the eastern Ladakh region.

拉达克喜马拉雅山是印度-欧亚交汇板块边缘演化历史的宝库。我们介绍了在拉达克东部沿 40 公里长的剖面横穿该板块边缘不同构造域进行的磁法（MT）研究的结果。我们采用二维（2-D）和三维（3-D）反演算法对 MT 数据集进行建模。通过对 18 个站点的畸变校正和分解数据进行二维反演得到的上地壳地电模型与地表地质非常吻合。在该模型中，印度河断裂带（ISZ）呈现为陡峭的倾斜接触，拉达克岩床厚约 10 至 12 千米。根据该模型，在措莫拉里（Tso Morari）结晶下 4 千米深处有一个直径为 6 千米的突出导体，其分支是沿印度河断裂带向上延伸的一个小导体。通过三维反演获得的地质电学模型与二维模型基本一致，但也揭示了一些非剖面特征，以及浅层导体与上地壳深层广泛导电带之间的联系。鉴于研究区域西面有普嘎温泉和楚玛塘温泉，东面有德木措温泉，我们推断这些导体代表了一个潜在的主要地热储层系统，与从西藏南部延伸到拉达克地区东部的广泛深层部分熔体导电带相连。

{"title":"A potential deep geothermal reservoir in eastern Ladakh as inferred from the upper crustal geoelectric structure of the region","authors":"","doi":"10.1016/j.pepi.2024.107263","DOIUrl":"10.1016/j.pepi.2024.107263","url":null,"abstract":"<div><div>The Ladakh Himalaya is a repository of the evolutionary history of the India-Eurasia convergent plate margin. We present the results of a magnetotelluric (MT) study carried out in Eastern Ladakh along a 40-km-long profile traversing across various tectonic domains of this plate margin. We modeled the MT dataset by two-dimensional (2-D) and three-dimensional (3-D) inversion algorithms. The upper crustal geoelectric model obtained by 2-D inversion of distortion corrected and decomposed data of 18 sites shows an excellent match with the surface geology. In this model, the Indus Suture Zone (ISZ) appears as a steeply dipping contact and the Ladakh batholith is about 10 to 12 km thick. The model yields a prominent electrical conductor of ∼6 km diameter at 4 km depth beneath the Tso Morari Crystallines with an offshoot of a small conductor that rises upward along the ISZ. The geoelectrical model obtained by 3-D inversion is broadly consistent with the 2-D model but also reveals off-profile features and a connectivity of the shallow conductors with a widespread conductive zone at deeper level of the upper crust. In view of the presence of Puga and Chumathang hot springs towards west and Demchok hot springs towards east of our study region, we infer these conductors to be representing a potential major geothermal reservoir system connected to the widespread deeper conductive zone of partial melts, which extends from the southern Tibet to the eastern Ladakh region.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

On the relationship between paleomagnetic secular variation and excursions – Records from MIS 11 and 12 – ODP Leg 172, western North Atlantic Ocean 古地磁世时变化与偏移之间的关系--MIS 11 和 12 的记录--ODP 第 172 工段，北大西洋西部

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-09-18 DOI: 10.1016/j.pepi.2024.107249

This study has developed paleomagnetic secular variation (PSV) records from Sites 1060, 1061, 1062, and 1063 (ODP Leg 172) from the western North Atlantic Ocean during MIS 11–12 (374–478 ka). We have identified 46 inclination features and 49 declination features that can be correlated among the records. We have also developed relative paleointensity records and identified 13 paleointensity features that can be correlated among them. These features can also be dated using the oxygen-isotope dated Global relative-paleointensity record PISO-1500 of Channell et al. (2009). There is one excursion located in these four records. We use the name Levantine/Bermuda Excursion developed elsewhere by Ryan (1972) and Channell et al. (2017). The Excursion occurred at 408 ± 4 ka. The excursion is recorded at Sites 1061, 1062, and 1063. The most detailed excursion records occur at Site 1062 where we have both shipboard PSV records and one u-channel PSV record of the excursion. The excursion has two intervals of excursional directions, one short interval (∼I ky) followed by a long interval (∼5 ky). Both intervals have counter-clockwise looping of the excursional directions and the excursion is considered to be a Class I Excursion (Lund et al., 2005). Statistical study of the PSV records after removal of the excursion directions has identified two characteristics of the ‘normal’ PSV. The first feature is a long-term (>10⁴ yrs) deviation in inclination and declination averages from the overall site averages. These deviations suggest some type on long-term memory in the regional dynamo process. The second feature is the variation in PSV angular dispersion (a measure of directional variability). The angular dispersion is quite low (∼12°) for most of the 374–478 ka interval. But, there is a short (∼8 ky) interval with angular dispersion more than double the amplitude (∼25°-30°). This interval has a sharp (<3 ky) onset and termination, This interval contains the Levantine/Bermuda Excursion. Such high-angular dispersion intervals with associated excursions and low paleointensity appear to be regular distinctive features of the Brunhes Chron PSV.

这项研究建立了北大西洋西部 1060、1061、1062 和 1063 号站点（ODP 第 172 工段）在 MIS 11-12 年（374-478 ka）期间的古地磁时变（PSV）记录。我们确定了 46 个倾角特征和 49 个偏角特征，这些特征可以在记录之间相互关联。我们还建立了相对古强度记录，并确定了 13 个可相互关联的古强度特征。这些特征还可以利用 Channell 等人（2009 年）的氧同位素年代全球相对古强度记录 PISO-1500 进行年代测定。这四条记录中有一条偏移。我们使用了 Ryan（1972 年）和 Channell 等人（2017 年）在其他地方提出的 Levantine/Bermuda Excursion 名称。这次偏移发生在 408 ± 4 ka。1061 号、1062 号和 1063 号地点都记录了这次偏移。最详细的偏移记录出现在 1062 号站点，在那里我们有船上 PSV 记录和一条 U-channel PSV 偏移记录。偏移方向有两个间隔，一个短间隔（∼I ky）和一个长间隔（∼5 ky）。这两个区间的偏移方向都是逆时针循环，偏移被认为是 I 级偏移（Lund 等人，2005 年）。去除偏移方向后对 PSV 记录进行的统计研究发现，"正常 "PSV 有两个特征。第一个特征是倾角和偏角的平均值长期（104 年）偏离整个站点的平均值。这些偏差表明区域动力过程中存在某种长期记忆。第二个特征是 PSV 角度离散度的变化（衡量方向可变性的指标）。在 374-478 ka 时段的大部分时间里，角度离散度相当低（∼12°）。但是，有一个很短（∼8 ky）的区间，其角度离散度是振幅的两倍多（∼25°-30°）。这个区间有一个急剧的（<3 ky）起始和终止点，这个区间包含 Levantine/Bermuda Excursion。这种具有相关偏移和低古强度的高角离散区间似乎是布鲁内斯年代PSV的规律性显著特征。

{"title":"On the relationship between paleomagnetic secular variation and excursions – Records from MIS 11 and 12 – ODP Leg 172, western North Atlantic Ocean","authors":"","doi":"10.1016/j.pepi.2024.107249","DOIUrl":"10.1016/j.pepi.2024.107249","url":null,"abstract":"<div><p>This study has developed paleomagnetic secular variation (PSV) records from Sites 1060, 1061, 1062, and 1063 (ODP Leg 172) from the western North Atlantic Ocean during MIS 11–12 (374–478 ka). We have identified 46 inclination features and 49 declination features that can be correlated among the records. We have also developed relative paleointensity records and identified 13 paleointensity features that can be correlated among them. These features can also be dated using the oxygen-isotope dated Global relative-paleointensity record PISO-1500 of Channell et al. (2009). There is one excursion located in these four records. We use the name Levantine/Bermuda Excursion developed elsewhere by Ryan (1972) and Channell et al. (2017). The Excursion occurred at 408 ± 4 ka. The excursion is recorded at Sites 1061, 1062, and 1063. The most detailed excursion records occur at Site 1062 where we have both shipboard PSV records and one u-channel PSV record of the excursion. The excursion has two intervals of excursional directions, one short interval (∼I ky) followed by a long interval (∼5 ky). Both intervals have counter-clockwise looping of the excursional directions and the excursion is considered to be a Class I Excursion (Lund et al., 2005). Statistical study of the PSV records after removal of the excursion directions has identified two characteristics of the ‘normal’ PSV. The first feature is a long-term (>10<sup>4</sup> yrs) deviation in inclination and declination averages from the overall site averages. These deviations suggest some type on long-term memory in the regional dynamo process. The second feature is the variation in PSV angular dispersion (a measure of directional variability). The angular dispersion is quite low (∼12°) for most of the 374–478 ka interval. But, there is a short (∼8 ky) interval with angular dispersion more than double the amplitude (∼25°-30°). This interval has a sharp (<3 ky) onset and termination, This interval contains the Levantine/Bermuda Excursion. Such high-angular dispersion intervals with associated excursions and low paleointensity appear to be regular distinctive features of the Brunhes Chron PSV.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Wudalianchi volcanism and mantle dynamics in Northeast China: New insight from Pn and Sn tomography 中国东北五大连池火山活动与地幔动力学：Pn和Sn层析成像的新见解

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-09-18 DOI: 10.1016/j.pepi.2024.107260

We determine new tomographic models of Pn anisotropic velocity and Sn isotropic velocity in and around the Wudalianchi volcanic area by inverting high-quality Pn and Sn arrival times manually picked from waveforms recorded at the newly deployed high-dense WAVESArray portable seismic stations. Our high-resolution Pn and Sn velocity models reveal strong lateral heterogeneities in the uppermost mantle under the study region. The average Pn and Sn velocities in the uppermost mantle are 8.2 and 4.5 km/s, respectively. Both Pn and Sn velocity models exhibit obvious low-velocity (low-V) anomalies under the Wudalianchi and Keluo volcanoes, whereas under the Songliao basin distinct high-velocity (high-V) zones are revealed. In particular, our Pn model reveals two separate low-V anomalies under the Nuominhe and Halaha volcanic groups, suggesting that they have different deep origins. A large-scale L-shaped low-V zone exists under the Keluo, Wudalianchi, Erkeshan, and Xunke volcanoes, characterized by Pn-wave fast propagation directions (FPDs) parallel with the low-V zone, suggesting that these volcanoes may have the same deep origin. Furthermore, southeast-opened U-shaped Pn FPDs exist around the Wudalianchi volcano, whereas NE-SW FPDs appear under the Great Xing'an range, which are generally consistent with SKS splitting measurements. This feature may reflect lithosphere-asthenosphere coupling beneath the Wudalianchi volcano associated with horizontal flows in the big mantle wedge and compressional tectonics under the Great Xing'an range. These results shed new lights on the Wudalianchi volcanism and mantle dynamics beneath Northeast China.

我们通过反演从新部署的高密度 WAVESArray 便携式地震台站记录的波形中人工选取的高质量 Pn 和 Sn 到达时间，确定了五大连池火山区及其周边地区 Pn 各向异性速度和 Sn 各向同性速度的新层析模型。我们的高分辨率 Pn 和 Sn 速度模型揭示了研究区域下最上层地幔强烈的横向异质性。最上地幔的平均 Pn 和 Sn 速度分别为每秒 8.2 公里和 4.5 公里。Pn和Sn速度模型在五大连池和开鲁火山下都显示出明显的低速（低V）异常，而在松辽盆地下则显示出明显的高速（高V）带。特别是，我们的Pn模型在诺敏河火山群和哈拉哈火山群下发现了两个独立的低V异常，这表明它们具有不同的深部起源。在凯洛火山群、五大连池火山群、额尔齐斯火山群和寻克火山群下存在一个大尺度的 L 型低 V 值区，其特征是 Pn 波快速传播方向（FPD）与低 V 值区平行，表明这些火山可能具有相同的深部起源。此外，五大连池火山周围存在东南向开口的U形Pn波快速传播方向（FPD），而大兴安岭下则出现东北-西南向的FPD，这与SKS劈裂测量结果基本一致。这一特征可能反映了五大连池火山下岩石圈-岩石圈耦合，与大地幔楔的水平流动和大兴安岭下的压缩构造有关。这些结果为五大连池火山活动和中国东北地下地幔动力学提供了新的线索。

{"title":"Wudalianchi volcanism and mantle dynamics in Northeast China: New insight from Pn and Sn tomography","authors":"","doi":"10.1016/j.pepi.2024.107260","DOIUrl":"10.1016/j.pepi.2024.107260","url":null,"abstract":"<div><div>We determine new tomographic models of Pn anisotropic velocity and Sn isotropic velocity in and around the Wudalianchi volcanic area by inverting high-quality Pn and Sn arrival times manually picked from waveforms recorded at the newly deployed high-dense WAVESArray portable seismic stations. Our high-resolution Pn and Sn velocity models reveal strong lateral heterogeneities in the uppermost mantle under the study region. The average Pn and Sn velocities in the uppermost mantle are 8.2 and 4.5 km/s, respectively. Both Pn and Sn velocity models exhibit obvious low-velocity (low-V) anomalies under the Wudalianchi and Keluo volcanoes, whereas under the Songliao basin distinct high-velocity (high-V) zones are revealed. In particular, our Pn model reveals two separate low-V anomalies under the Nuominhe and Halaha volcanic groups, suggesting that they have different deep origins. A large-scale L-shaped low-V zone exists under the Keluo, Wudalianchi, Erkeshan, and Xunke volcanoes, characterized by Pn-wave fast propagation directions (FPDs) parallel with the low-V zone, suggesting that these volcanoes may have the same deep origin. Furthermore, southeast-opened U-shaped Pn FPDs exist around the Wudalianchi volcano, whereas NE-SW FPDs appear under the Great Xing'an range, which are generally consistent with SKS splitting measurements. This feature may reflect lithosphere-asthenosphere coupling beneath the Wudalianchi volcano associated with horizontal flows in the big mantle wedge and compressional tectonics under the Great Xing'an range. These results shed new lights on the Wudalianchi volcanism and mantle dynamics beneath Northeast China.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142310256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Randomization of the Earth's magnetic field driven by magnetic helicity 磁螺旋驱动的地球磁场随机化

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-09-18 DOI: 10.1016/j.pepi.2024.107250

It is shown, using results of numerical simulations and geomagnetic observations, that the spatial and temporal randomization of the Earth's global and local magnetic fields is driven by magnetic helicity (an ideal magnetohydrodynamic invariant). In the frames of the distributed chaos notion, the magnetic helicity determines the degree of magnetic field randomization and the results of numerical simulations are in quantitative agreement with the geophysical observations despite the considerable differences in the scales and physical parameters.

利用数值模拟和地磁观测结果表明，地球全球和局部磁场的时空随机化是由磁螺旋度（理想的磁流体力学不变量）驱动的。在分布式混沌概念的框架内，磁螺旋决定了磁场随机化的程度，尽管尺度和物理参数存在很大差异，但数值模拟结果与地球物理观测结果在数量上是一致的。

引用次数: 0

Space and time distribution of seismic source energy at Campi Flegrei, Italy through the last unrest phase (1.1.2000–31.12.2023) 意大利坎皮弗莱格雷最后一个动荡阶段（2000 年 1 月 1 日至 2023 年 12 月 31 日）的震源能量时空分布情况

IF 2.4 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Physics of the Earth and Planetary Interiors

Pub Date : 2024-09-17 DOI: 10.1016/j.pepi.2024.107258

<div><p>We describe the space-time pattern of seismicity occurring on Campi Flegrei Caldera (CFC), Italy, where ground deformations and seismicity represent the drivers of its current bradyseismic crisis, well known and extensively studied at an international level. In detail we consider the seismicity in the time interval starting on 1.1.2000 and ending on 31.12.2023. We revise the statistics of the earthquake occurrence, focusing at possible precursory time changes of the b-parameter of the Gutenberg and Richter (G&R <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span>) distribution and at the time distribution of the total seismic moment inside any swarm. To estimate the G&R <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> we use a Monte Carlo method instead of the ordinary Least Squares or Maximum likelihood methods, to easily measure the uncertainty on the <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> taking into account uncertainties on the magnitude estimates. Results show that G&R <span><math><mi>a</mi><mo>−</mo><mi>value</mi></math></span> and <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> calculated for cumulative and discrete distributions of <span><math><msub><mi>M</mi><mi>w</mi></msub></math></span>, the moment-magnitude, and <span><math><msub><mi>M</mi><mi>d</mi></msub></math></span>, the so-called duration-magnitude, are the same inside the uncertainties; <span><math><mi>a</mi><mo>−</mo><mi>value</mi></math></span> and <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> for <span><math><msub><mi>M</mi><mi>d</mi></msub></math></span> are significantly different from the same parameters estimated for <span><math><msub><mi>M</mi><mi>w</mi></msub></math></span>, being <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> for <span><math><msub><mi>M</mi><mi>w</mi></msub></math></span> close to the value of 1.0 and <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> for <span><math><msub><mi>M</mi><mi>d</mi></msub></math></span> close to 0.8. The “bounded” G&R distribution fits the data yielding <span><math><mi>a</mi><mo>−</mo><mi>value</mi></math></span> and <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> close to those for the unbounded distribution. The mean annual rate of exceedance, calculated for the entire catalogue, results to be 0.033<span><math><mo>±</mo><mn>0.015</mn></math></span> (years<sup>−1</sup>) corresponding to a return period of <span><math><mn>30</mn><mo>±</mo><mn>14</mn></math></span> years for <span><math><msub><mi>M</mi><mi>w</mi></msub><mo>=</mo><mn>4.5</mn></math></span>. The time dependence of G&R b-parameter show a <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> time pattern characterized by variations slightly outside 1-<span><math><mi>σ</mi></math></span> uncertainty bar, tending to the value of 1 approaching present. As evidenced by several past studies, earthquakes in CFC occur in space-t

我们描述了发生在意大利坎皮弗莱格雷火山口（Campi Flegrei Caldera，CFC）的地震时空模式，地面变形和地震是该火山口当前缓震危机的驱动因素。我们详细考虑了从 2000 年 1 月 1 日到 2023 年 12 月 31 日这段时间内的地震情况。我们修订了地震发生的统计数据，重点关注古腾堡和里氏（G&R b 值）分布的 b 参数可能发生的前兆时间变化，以及任何震群内部总地震力矩的时间分布。为了估算 G&R b 值，我们使用蒙特卡罗方法而不是普通的最小二乘法或最大似然法，以便在考虑震级估算的不确定性的同时，轻松测量 b 值的不确定性。结果表明，在不确定性范围内，为时刻幅度 Mw 和持续时间幅度 Md 的累积分布和离散分布计算出的 G&R a 值和 b 值是相同的；Md 的 a 值和 b 值与 Mw 的相同参数估计值有显著差异，Mw 的 b 值接近 1.0，Md 的 b 值接近 0.8。有界 "G&R 分布与数据拟合，得出的 a 值和 b 值与无界分布接近。计算整个目录的年平均超标率为 0.033±0.015（年-1），对应于 Mw=4.5 时 30±14 年的回归期。G&R b参数的时间依赖性显示了一个b值时间模式，其特点是变化略微超出1-σ的不确定性条，趋向于接近1的值。过去的一些研究表明，CFC 地震发生在时空群中，平均持续时间为 1 天。我们根据对连续事件偶的到达时间和事件间距离的联合估计，用选择算法选出了地震群。每个群中的事件数与发生时间的对比图清楚地表明，在 CFC 中，从 2010 年开始，群发生的次数和每个群中的事件数都在加速增长。每个震群的总地震力矩的时间模式表明，与事件数相反，震群总地震力矩并没有随着时间的推移而明显增加。这一数据显示，在过去的 15 个月中，断裂岩石体积明显向西扩大，深度在海平面以下 3000 米左右。本研究证实，当前的动荡阶段仍在持续，与 22 个月前相比，岩石断裂带向南、向西扩展。

{"title":"Space and time distribution of seismic source energy at Campi Flegrei, Italy through the last unrest phase (1.1.2000–31.12.2023)","authors":"","doi":"10.1016/j.pepi.2024.107258","DOIUrl":"10.1016/j.pepi.2024.107258","url":null,"abstract":"<div><p>We describe the space-time pattern of seismicity occurring on Campi Flegrei Caldera (CFC), Italy, where ground deformations and seismicity represent the drivers of its current bradyseismic crisis, well known and extensively studied at an international level. In detail we consider the seismicity in the time interval starting on 1.1.2000 and ending on 31.12.2023. We revise the statistics of the earthquake occurrence, focusing at possible precursory time changes of the b-parameter of the Gutenberg and Richter (G&R <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span>) distribution and at the time distribution of the total seismic moment inside any swarm. To estimate the G&R <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> we use a Monte Carlo method instead of the ordinary Least Squares or Maximum likelihood methods, to easily measure the uncertainty on the <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> taking into account uncertainties on the magnitude estimates. Results show that G&R <span><math><mi>a</mi><mo>−</mo><mi>value</mi></math></span> and <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> calculated for cumulative and discrete distributions of <span><math><msub><mi>M</mi><mi>w</mi></msub></math></span>, the moment-magnitude, and <span><math><msub><mi>M</mi><mi>d</mi></msub></math></span>, the so-called duration-magnitude, are the same inside the uncertainties; <span><math><mi>a</mi><mo>−</mo><mi>value</mi></math></span> and <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> for <span><math><msub><mi>M</mi><mi>d</mi></msub></math></span> are significantly different from the same parameters estimated for <span><math><msub><mi>M</mi><mi>w</mi></msub></math></span>, being <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> for <span><math><msub><mi>M</mi><mi>w</mi></msub></math></span> close to the value of 1.0 and <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> for <span><math><msub><mi>M</mi><mi>d</mi></msub></math></span> close to 0.8. The “bounded” G&R distribution fits the data yielding <span><math><mi>a</mi><mo>−</mo><mi>value</mi></math></span> and <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> close to those for the unbounded distribution. The mean annual rate of exceedance, calculated for the entire catalogue, results to be 0.033<span><math><mo>±</mo><mn>0.015</mn></math></span> (years<sup>−1</sup>) corresponding to a return period of <span><math><mn>30</mn><mo>±</mo><mn>14</mn></math></span> years for <span><math><msub><mi>M</mi><mi>w</mi></msub><mo>=</mo><mn>4.5</mn></math></span>. The time dependence of G&R b-parameter show a <span><math><mi>b</mi><mo>−</mo><mi>value</mi></math></span> time pattern characterized by variations slightly outside 1-<span><math><mi>σ</mi></math></span> uncertainty bar, tending to the value of 1 approaching present. As evidenced by several past studies, earthquakes in CFC occur in space-t","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":null,"pages":null},"PeriodicalIF":2.4,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S003192012400116X/pdfft?md5=a859af686a6ea4310c7c90813110214b&pid=1-s2.0-S003192012400116X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142272089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0