Pub Date : 2025-11-01DOI: 10.1016/j.pepi.2025.107460
Ján Šimkanin
Changes in the geomagnetic field corresponding to the Earth’s inner core growth are numerically investigated. The Geodynamo is driven by thermochemical convection in the Earth’s outer core, with the codensity gradient serving as the primary driving force. Simulations begin with a small inner core (‘Past’), which progressively enlarges until reaching a stage where the inner core becomes dominant (‘Future’). During the ’Past’ stage, the Geodynamo model generates a multipolar geomagnetic field, which gradually transitions into a predominantly dipolar field as the inner core grows. These transitions are also accompanied by shifts between weak-field and strong-field dynamos and vice versa. The ratio of magnetic to kinetic energy emerges as a more reliable parameter for controlling the transition from multipolar to dipolar dynamos. The dipole component for a small inner core proves unstable, with frequent polarity reversals. As the inner core grows, the frequency of these reversals decreases until the ‘Present’ case, where polarity reversals cease entirely. It is important to note that during the ‘Past’, fluctuations in dipole polarity are observed even in a dipole-dominated magnetic field. In the ‘Future’ stage, representing a potential scenario for the Earth’s geomagnetic field, the hydromagnetic dynamo produces a dipole-dominated magnetic field without polarity reversals. However, if the Earth’s liquid outer core becomes exceedingly small, convection diminishes, causing the Geodynamo to fail. This leads to a slow decay of the magnetic field due to magnetic diffusion. During the ’Future’ stage, the emergence of subcritical dynamos is observed. It is important to note that the results of the present analysis are more strongly influenced by the supercriticality of the flow than by the inner core size, as the latter is determined by the selected solution parameters.
{"title":"Geomagnetic field and the growth of the Earth’s inner core: Past, present and future","authors":"Ján Šimkanin","doi":"10.1016/j.pepi.2025.107460","DOIUrl":"10.1016/j.pepi.2025.107460","url":null,"abstract":"<div><div>Changes in the geomagnetic field corresponding to the Earth’s inner core growth are numerically investigated. The Geodynamo is driven by thermochemical convection in the Earth’s outer core, with the codensity gradient serving as the primary driving force. Simulations begin with a small inner core (‘Past’), which progressively enlarges until reaching a stage where the inner core becomes dominant (‘Future’). During the ’Past’ stage, the Geodynamo model generates a multipolar geomagnetic field, which gradually transitions into a predominantly dipolar field as the inner core grows. These transitions are also accompanied by shifts between weak-field and strong-field dynamos and vice versa. The ratio of magnetic to kinetic energy emerges as a more reliable parameter for controlling the transition from multipolar to dipolar dynamos. The dipole component for a small inner core proves unstable, with frequent polarity reversals. As the inner core grows, the frequency of these reversals decreases until the ‘Present’ case, where polarity reversals cease entirely. It is important to note that during the ‘Past’, fluctuations in dipole polarity are observed even in a dipole-dominated magnetic field. In the ‘Future’ stage, representing a potential scenario for the Earth’s geomagnetic field, the hydromagnetic dynamo produces a dipole-dominated magnetic field without polarity reversals. However, if the Earth’s liquid outer core becomes exceedingly small, convection diminishes, causing the Geodynamo to fail. This leads to a slow decay of the magnetic field due to magnetic diffusion. During the ’Future’ stage, the emergence of subcritical dynamos is observed. It is important to note that the results of the present analysis are more strongly influenced by the supercriticality of the flow than by the inner core size, as the latter is determined by the selected solution parameters.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107460"},"PeriodicalIF":1.9,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416692","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}
Pub Date : 2025-11-01DOI: 10.1016/j.pepi.2025.107459
Clemens Kloss
Studies of Earth’s magnetic field and its sources rely on accurate geomagnetic field models derived from ground and satellite-based magnetic data. During the field model estimation, data errors are usually assumed to be uncorrelated in time and independent of position. However, limitations in the field model parameterization, especially regarding ionospheric and magnetospheric fields, lead to data errors that are not only larger than the expected measurement noise but are also correlated in time and vary with position. As a result, the obtained model uncertainties are often underestimated, making it more challenging to evaluate the reliability of recovered signals in the field models.
This study investigates the effect of including correlated data errors in field modeling. The approach involves building a stochastic data error model to treat correlated errors due to unmodeled magnetospheric fields within the CHAOS geomagnetic field modeling framework. The error model parameters are estimated using empirical covariances computed from vector residuals between the satellite magnetic observations made by the Swarm satellites and the CHAOS geomagnetic field model. Field modeling experiments are performed with and without including the data error covariances described in the stochastic error model.
The inclusion of data error covariances due to unmodeled magnetospheric fields leads to only small changes in the estimated internal field, but also a noticeable increase in model uncertainty for the sectoral coefficients. This highlights the significant impact of unmodeled magnetospheric fields and the importance of accurately defining data errors, including the covariances between observations, for interpreting the retrieved magnetic signals in geomagnetic field modeling.
{"title":"Accounting for correlated data errors in geomagnetic field modeling using Swarm magnetic observations","authors":"Clemens Kloss","doi":"10.1016/j.pepi.2025.107459","DOIUrl":"10.1016/j.pepi.2025.107459","url":null,"abstract":"<div><div>Studies of Earth’s magnetic field and its sources rely on accurate geomagnetic field models derived from ground and satellite-based magnetic data. During the field model estimation, data errors are usually assumed to be uncorrelated in time and independent of position. However, limitations in the field model parameterization, especially regarding ionospheric and magnetospheric fields, lead to data errors that are not only larger than the expected measurement noise but are also correlated in time and vary with position. As a result, the obtained model uncertainties are often underestimated, making it more challenging to evaluate the reliability of recovered signals in the field models.</div><div>This study investigates the effect of including correlated data errors in field modeling. The approach involves building a stochastic data error model to treat correlated errors due to unmodeled magnetospheric fields within the CHAOS geomagnetic field modeling framework. The error model parameters are estimated using empirical covariances computed from vector residuals between the satellite magnetic observations made by the <em>Swarm</em> satellites and the CHAOS geomagnetic field model. Field modeling experiments are performed with and without including the data error covariances described in the stochastic error model.</div><div>The inclusion of data error covariances due to unmodeled magnetospheric fields leads to only small changes in the estimated internal field, but also a noticeable increase in model uncertainty for the sectoral coefficients. This highlights the significant impact of unmodeled magnetospheric fields and the importance of accurately defining data errors, including the covariances between observations, for interpreting the retrieved magnetic signals in geomagnetic field modeling.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107459"},"PeriodicalIF":1.9,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145416691","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}
Pub Date : 2025-10-30DOI: 10.1016/j.pepi.2025.107463
Charles-Édouard Boukaré , Laura K. Schaefer , Hanika Rizo
To celebrate over 55 years of Physics of the Earth and Planetary Interiors providing a venue for communicating advancements in the chemical and dynamical processes that lead to planetary differentiation, we revisit Earth’s magma ocean in light of the seminal works of Ohtani (1983); Abe and Matsui (1986). Models of Earth’s formation suggest a hot initial state in which much of the planet’s interior was substantially, if not entirely, molten. The global-scale molten silicate mantle is referred to as a magma ocean. Because elements of the periodic table show different affinities for liquid, solid, and gaseous phases, the transition from a molten to a solid mantle provides a key window for early chemical differentiation, with profound implications for Earth’s long-term evolution. The magma ocean hypothesis has been extensively studied in the context of the Moon’s evolution. Major advances in our understanding of the lunar magma ocean have been enabled by experimental access to relevant petrological conditions. Pioneering studies by Ohtani (1983); Abe and Matsui (1986); Solomatov and Stevenson (1993c); Abe (1997) explored magma ocean processes in the context of the Earth, and although high-pressure data for Earth’s mantle were limited at the time, these studies correctly anticipated much of the physics now central to early Earth models. Recent developments, including analyses of short-lived isotopic systems, high pressure experiments using diamond anvil cells, and ab-initio calculations are now providing new constraints on models of Earth’s magma ocean. This review summarizes these recent advances and how they change our understanding of the Earth’s magma ocean evolution. We also discuss the current challenges in developing an interdisciplinary yet coherent picture of the Earth’s earliest evolutionary stages.
为了庆祝超过55年的地球和行星内部物理学，提供了一个交流导致行星分化的化学和动力学过程进展的场所，我们根据大谷（1983）的开创性作品重新审视了地球的岩浆海洋；安倍和松井（1986）。地球形成的模型表明，在一个炎热的初始状态下，地球内部的大部分（如果不是全部的话）基本上是熔融的。全球范围的熔融硅酸盐地幔被称为岩浆海洋。由于元素周期表上的元素在液态、固态和气态阶段表现出不同的亲和力，从熔融地幔到固态地幔的转变为早期化学分化提供了一个关键窗口，对地球的长期演化具有深远的影响。岩浆海洋假说在月球演化的背景下得到了广泛的研究。我们对月球岩浆海洋的认识取得了重大进展，这是通过对相关岩石学条件的实验获得的。Ohtani（1983）的开创性研究；安倍和松井（1986）；Solomatov and Stevenson (1993c)；Abe（1997）在地球的背景下探索了岩浆海洋过程，尽管当时地幔的高压数据有限，但这些研究正确地预测了许多现在对早期地球模型至关重要的物理学。最近的发展，包括对短寿命同位素系统的分析，利用金刚石砧细胞进行的高压实验，以及从头算，现在为地球岩浆海洋的模型提供了新的限制。本文综述了这些最新进展，以及它们如何改变我们对地球岩浆海洋演化的认识。我们还讨论了目前在发展地球最早进化阶段的跨学科但连贯的图片所面临的挑战。
{"title":"The Earth’s magma ocean: Processes and current interpretations from an interdisciplinary perspective","authors":"Charles-Édouard Boukaré , Laura K. Schaefer , Hanika Rizo","doi":"10.1016/j.pepi.2025.107463","DOIUrl":"10.1016/j.pepi.2025.107463","url":null,"abstract":"<div><div>To celebrate over 55 years of Physics of the Earth and Planetary Interiors providing a venue for communicating advancements in the chemical and dynamical processes that lead to planetary differentiation, we revisit Earth’s magma ocean in light of the seminal works of Ohtani (1983); Abe and Matsui (1986). Models of Earth’s formation suggest a hot initial state in which much of the planet’s interior was substantially, if not entirely, molten. The global-scale molten silicate mantle is referred to as a magma ocean. Because elements of the periodic table show different affinities for liquid, solid, and gaseous phases, the transition from a molten to a solid mantle provides a key window for early chemical differentiation, with profound implications for Earth’s long-term evolution. The magma ocean hypothesis has been extensively studied in the context of the Moon’s evolution. Major advances in our understanding of the lunar magma ocean have been enabled by experimental access to relevant petrological conditions. Pioneering studies by Ohtani (1983); Abe and Matsui (1986); Solomatov and Stevenson (1993c); Abe (1997) explored magma ocean processes in the context of the Earth, and although high-pressure data for Earth’s mantle were limited at the time, these studies correctly anticipated much of the physics now central to early Earth models. Recent developments, including analyses of short-lived isotopic systems, high pressure experiments using diamond anvil cells, and ab-initio calculations are now providing new constraints on models of Earth’s magma ocean. This review summarizes these recent advances and how they change our understanding of the Earth’s magma ocean evolution. We also discuss the current challenges in developing an interdisciplinary yet coherent picture of the Earth’s earliest evolutionary stages.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"369 ","pages":"Article 107463"},"PeriodicalIF":1.9,"publicationDate":"2025-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145468950","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}
MgO is the end-member of the primary constituents of the lower mantle, and identifying its crystal preferred orientation (CPO) developments or slip systems is key to understanding seismic observations and the dynamics of the lower mantle. To investigate the temperature dependence on CPO developments in MgO under high-pressure conditions corresponding to the lower mantle, we conducted large-strain deformation experiments using the rotational diamond anvil cell (rDAC) combined with synchrotron X-rays, achieving pressures up to 80 GPa and temperatures up to 973 K. Our results revealed that the CPO developments in MgO under large-strain deformation are temperature-dependent even at relatively low temperatures. The crystal plane parallel to the shear plane changed from the {110} plane to the {100} plane with increasing temperature and pressure. Based on our experimental results, we constructed a temperature-pressure map that shows the CPO variation of MgO. The temperature-pressure map obtained in this study provides essential foundational information for advancing our understanding of rheology in the lower mantle.
{"title":"Temperature and pressure dependence on slip systems in MgO: Insights from large-strain deformation experiments using the rotational diamond anvil cell","authors":"Keiya Ishimori , Shintaro Azuma , Kentaro Uesugi , Masahiro Yasutake , Keishi Okazaki , Bunrin Natsui , Eranga Gyanath Jayawickrama , Kenji Ohta","doi":"10.1016/j.pepi.2025.107461","DOIUrl":"10.1016/j.pepi.2025.107461","url":null,"abstract":"<div><div>MgO is the end-member of the primary constituents of the lower mantle, and identifying its crystal preferred orientation (CPO) developments or slip systems is key to understanding seismic observations and the dynamics of the lower mantle. To investigate the temperature dependence on CPO developments in MgO under high-pressure conditions corresponding to the lower mantle, we conducted large-strain deformation experiments using the rotational diamond anvil cell (rDAC) combined with synchrotron X-rays, achieving pressures up to 80 GPa and temperatures up to 973 K. Our results revealed that the CPO developments in MgO under large-strain deformation are temperature-dependent even at relatively low temperatures. The crystal plane parallel to the shear plane changed from the {110} plane to the {100} plane with increasing temperature and pressure. Based on our experimental results, we constructed a temperature-pressure map that shows the CPO variation of MgO. The temperature-pressure map obtained in this study provides essential foundational information for advancing our understanding of rheology in the lower mantle.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"369 ","pages":"Article 107461"},"PeriodicalIF":1.9,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145435476","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}
We present a simple linear equation to calculate the degree of melting of the mantle using the major element composition of basalts. We constructed a model based on compiled results from high-pressure mantle melting experiments. We used a model selection approach to objectively select the optimal equation from many potential models, based on statistical criteria. We found that the degree of mantle melting () can be predicted with a simple equation that uses only the concentrations of three major elements, which are , FeO (total iron as FeO), and MgO (wt.%), as follows:
The model allows us to calculate the degree of melting of the uppermost upper mantle (spinel lherzolite and harzburgite), under both anhydrous and hydrous conditions. The equation yields the equilibrium degree of melting in the case of batch melting, and the weighted-mean degree of melting of accumulated melt in the case of fractional melting. We also describe the petrological and thermodynamic implications of the equation. The degrees of melting of natural basalts are calculated as examples of the application of the equation.
{"title":"A simple linear regression model for calculating the degree of melting of the upper mantle using the major element composition of basalts","authors":"Kenta Ueki , Satoru Haraguchi , Atsushi Nakao , Hikaru Iwamori","doi":"10.1016/j.pepi.2025.107464","DOIUrl":"10.1016/j.pepi.2025.107464","url":null,"abstract":"<div><div>We present a simple linear equation to calculate the degree of melting of the mantle using the major element composition of basalts. We constructed a model based on compiled results from high-pressure mantle melting experiments. We used a model selection approach to objectively select the optimal equation from many potential models, based on statistical criteria. We found that the degree of mantle melting (<span><math><mi>F</mi></math></span>) can be predicted with a simple equation that uses only the concentrations of three major elements, which are <span><math><msub><mrow><mi>SiO</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, FeO<span><math><msup><mrow></mrow><mrow><mo>∗</mo></mrow></msup></math></span> (total iron as FeO), and MgO (wt.%), as follows:</div><div><span><math><mrow><mi>F</mi><mrow><mo>(</mo><mi>wt</mi><mo>.</mo><mtext>%</mtext><mo>)</mo></mrow><mo>=</mo><mn>4</mn><mo>.</mo><mn>020</mn><mo>×</mo><msub><mrow><mi>SiO</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>+</mo><mn>5</mn><mo>.</mo><mn>109</mn><mo>×</mo><msup><mrow><mi>FeO</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>+</mo><mn>1</mn><mo>.</mo><mn>436</mn><mo>×</mo><mi>MgO</mi><mo>−</mo><mn>244</mn><mo>.</mo><mn>924</mn><mo>.</mo></mrow></math></span></div><div>The model allows us to calculate the degree of melting of the uppermost upper mantle (spinel lherzolite and harzburgite), under both anhydrous and hydrous conditions. The equation yields the equilibrium degree of melting in the case of batch melting, and the weighted-mean degree of melting of accumulated melt in the case of fractional melting. We also describe the petrological and thermodynamic implications of the equation. The degrees of melting of natural basalts are calculated as examples of the application of the equation.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107464"},"PeriodicalIF":1.9,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362498","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}
Pub Date : 2025-10-18DOI: 10.1016/j.pepi.2025.107462
Zhiwei Zhang , Feng Long , Chaoliang Wang , Weiming Wang , Di Wang , Qian Lu , Chuntao Liang
The 17 June 2019 Changning MS 6.0 earthquake occurred half a year after the 2018 Xingwen MS 5.7 earthquake in the Sichuan Basin, China. Even though the two earthquakes are only 15 km apart, their focal mechanism solutions are different. The stress regime is critical to revealing the mechanisms of moderate earthquakes in the industrial mining region. In this study, we used the CAP full waveform method to calculate the focal mechanism solution, relocated the aftershocks using a hybrid multi-stage method, and further discussed the stress trigger relationship of the two events. The results show that the seismogenic structure of the Changning earthquake is related to the Shuanghe anticline and Baixiangyan-Shizitan anticline and their associated faults, while the Xingwen earthquake may occur on the hidden fault between the Changning anticline and the Jianwu syncline. The azimuth of the maximum principal compressive stress (S1) is NEE in the Changning area and NWW in the Xingwen area, The S1 direction in the Changning area is inconsistent with the stress field (NW) in southeast Sichuan, the perturbation of the local stress field reveals that the influence of long-term salt injection in the Changning area is more obvious than that of short-term hydraulic fracturing in the Xingwen area. Moreover, the Xingwen MS 5.7 earthquake may play a triggering role in the Changning MS 6.0 earthquake via static stress transfer.
{"title":"Probing the seismogenic mechanisms of the Changning MS 6.0 and Xingwen MS 5.7 earthquakes in the Sichuan Basin, China","authors":"Zhiwei Zhang , Feng Long , Chaoliang Wang , Weiming Wang , Di Wang , Qian Lu , Chuntao Liang","doi":"10.1016/j.pepi.2025.107462","DOIUrl":"10.1016/j.pepi.2025.107462","url":null,"abstract":"<div><div>The 17 June 2019 Changning <em>M</em><sub>S</sub> 6.0 earthquake occurred half a year after the 2018 Xingwen <em>M</em><sub>S</sub> 5.7 earthquake in the Sichuan Basin, China. Even though the two earthquakes are only 15 km apart, their focal mechanism solutions are different. The stress regime is critical to revealing the mechanisms of moderate earthquakes in the industrial mining region. In this study, we used the CAP full waveform method to calculate the focal mechanism solution, relocated the aftershocks using a hybrid multi-stage method, and further discussed the stress trigger relationship of the two events. The results show that the seismogenic structure of the Changning earthquake is related to the Shuanghe anticline and Baixiangyan-Shizitan anticline and their associated faults, while the Xingwen earthquake may occur on the hidden fault between the Changning anticline and the Jianwu syncline. The azimuth of the maximum principal compressive stress (S<sub>1</sub>) is NEE in the Changning area and NWW in the Xingwen area, The S<sub>1</sub> direction in the Changning area is inconsistent with the stress field (NW) in southeast Sichuan, the perturbation of the local stress field reveals that the influence of long-term salt injection in the Changning area is more obvious than that of short-term hydraulic fracturing in the Xingwen area. Moreover, the Xingwen <em>M</em><sub>S</sub> 5.7 earthquake may play a triggering role in the Changning <em>M</em><sub>S</sub> 6.0 earthquake via static stress transfer.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107462"},"PeriodicalIF":1.9,"publicationDate":"2025-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362496","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}
Pub Date : 2025-10-08DOI: 10.1016/j.pepi.2025.107458
Jinfeng Li , Yufeng Lin , Keke Zhang
The dynamics of Earth’s liquid outer core are essential for understanding geomagnetic field variations. Conventional kinematic inversion methods are typically limited to recovering flow structures near the core–mantle boundary. In contrast, dynamic inversion approaches such as geomagnetic data assimilation have the potential to retrieve flow structures at greater depths. However, the practical application of dynamic inversion remains challenging due to observational limitations and computational constraints. In this study, we propose an inversion method that lies between the kinematic and dynamic approaches. It is based on the full vector form of the magnetic induction equation under the frozen flux assumption combined with an inertial mode representation of the flow. This method leverages the expected rotation-dominated core flows together with observational constraints, enabling the recovery of both core-surface flows and some deeper flow structures. The inversion process is realized through physics-informed neural networks. Synthetic dynamo simulations demonstrate that our inversion framework is able to capture large-scale 3-D core flow patterns. Moreover, by utilizing high-precision magnetic data from the Swarm constellation and the Macau Science Satellite-1, we reconstruct a 3-D core flow model within Earth’s outer core over the past decade. Our 3-D core flow model reveals a dominant planetary gyre in the Atlantic hemisphere and pronounced shear-induced helical flow structures in the Pacific hemisphere, characterized by significant downwelling beneath Latin America and upwelling beneath the Indian Ocean.
{"title":"Reconstruction of 3-D core flows using magnetic data from Swarm and MSS-1","authors":"Jinfeng Li , Yufeng Lin , Keke Zhang","doi":"10.1016/j.pepi.2025.107458","DOIUrl":"10.1016/j.pepi.2025.107458","url":null,"abstract":"<div><div>The dynamics of Earth’s liquid outer core are essential for understanding geomagnetic field variations. Conventional kinematic inversion methods are typically limited to recovering flow structures near the core–mantle boundary. In contrast, dynamic inversion approaches such as geomagnetic data assimilation have the potential to retrieve flow structures at greater depths. However, the practical application of dynamic inversion remains challenging due to observational limitations and computational constraints. In this study, we propose an inversion method that lies between the kinematic and dynamic approaches. It is based on the full vector form of the magnetic induction equation under the frozen flux assumption combined with an inertial mode representation of the flow. This method leverages the expected rotation-dominated core flows together with observational constraints, enabling the recovery of both core-surface flows and some deeper flow structures. The inversion process is realized through physics-informed neural networks. Synthetic dynamo simulations demonstrate that our inversion framework is able to capture large-scale 3-D core flow patterns. Moreover, by utilizing high-precision magnetic data from the Swarm constellation and the Macau Science Satellite-1, we reconstruct a 3-D core flow model within Earth’s outer core over the past decade. Our 3-D core flow model reveals a dominant planetary gyre in the Atlantic hemisphere and pronounced shear-induced helical flow structures in the Pacific hemisphere, characterized by significant downwelling beneath Latin America and upwelling beneath the Indian Ocean.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107458"},"PeriodicalIF":1.9,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145320409","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}
Pub Date : 2025-10-03DOI: 10.1016/j.pepi.2025.107457
Mohammad Filbandi Kashkouli , Matthew J. Comeau , Abolghasem Kamkar-Rouhani , Alireza Arab-Amiri
Salt diapirs are prominent geological features, formed by the piercing of buoyant salt within overlying strata, with implications for basin evolution, tectonic deformation, and resource accumulation. In this study, we investigate the Shurab salt diapirs in northwestern Central Iran—an area with five known near-surface diapirs—whose subsurface geometries and interconnections at depth remain unclear due to the complex structural settings. To address these challenges, we generated a 3D electrical resistivity model from an array of 183 magnetotelluric (MT) measurements. Phase tensor and resistivity phase tensor analyses confirmed the presence of multidimensional conductivity structures. A range of modeling tests were performed to ensure a robust result, and final models were validated against seismic data and borehole logs, as well as previous 2D electric modeling. The resulting 3D resistivity model provides new insight into the geometry, depth, and interconnectedness of the salt diapirs and superior resolution of diapir flanks compared to seismic data. High resistivity zones at shallow depths correspond to dry salt, while lower resistivity at greater depths indicates brine-saturated regions. Notably, Diapirs No. 4 and 5 were found to be interconnected at depth, sharing a root zone and likely originating from a common evaporite layer. Tectonic analysis suggests that active fault systems—including the Sen-Sen, Ab-Shirin, and Dehnar faults—have played key roles in guiding salt migration and shaping diapir structures. This study highlights the effectiveness of using MT data to image complex salt structures and underscores the importance of integrated geophysical approaches in tectonically active regions.
{"title":"Improved characterization of the 3D structure of salt diapirs with electrical resistivity models","authors":"Mohammad Filbandi Kashkouli , Matthew J. Comeau , Abolghasem Kamkar-Rouhani , Alireza Arab-Amiri","doi":"10.1016/j.pepi.2025.107457","DOIUrl":"10.1016/j.pepi.2025.107457","url":null,"abstract":"<div><div>Salt diapirs are prominent geological features, formed by the piercing of buoyant salt within overlying strata, with implications for basin evolution, tectonic deformation, and resource accumulation. In this study, we investigate the Shurab salt diapirs in northwestern Central Iran—an area with five known near-surface diapirs—whose subsurface geometries and interconnections at depth remain unclear due to the complex structural settings. To address these challenges, we generated a 3D electrical resistivity model from an array of 183 magnetotelluric (MT) measurements. Phase tensor and resistivity phase tensor analyses confirmed the presence of multidimensional conductivity structures. A range of modeling tests were performed to ensure a robust result, and final models were validated against seismic data and borehole logs, as well as previous 2D electric modeling. The resulting 3D resistivity model provides new insight into the geometry, depth, and interconnectedness of the salt diapirs and superior resolution of diapir flanks compared to seismic data. High resistivity zones at shallow depths correspond to dry salt, while lower resistivity at greater depths indicates brine-saturated regions. Notably, Diapirs No. 4 and 5 were found to be interconnected at depth, sharing a root zone and likely originating from a common evaporite layer. Tectonic analysis suggests that active fault systems—including the Sen-Sen, Ab-Shirin, and Dehnar faults—have played key roles in guiding salt migration and shaping diapir structures. This study highlights the effectiveness of using MT data to image complex salt structures and underscores the importance of integrated geophysical approaches in tectonically active regions.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107457"},"PeriodicalIF":1.9,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145320564","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}
Pub Date : 2025-09-24DOI: 10.1016/j.pepi.2025.107456
Ming Gong , Michael I. Bergman
Seismic attenuation can be intrinsic or due to scattering. The relative role of each for Earth's inner core is uncertain. Whereas intrinsic attenuation depends primarily on the material, temperature, and pressure, scattering is primarily a function of microstructure, that is, grain size, shape, texture, as well as single-crystal elastic anisotropy. Here we studied experimentally scattering of ultrasonic compressional waves in a hexagonal close-packed (hcp) Zn-rich Sn alloy, for two microstructures that are likely relevant to the inner core: textured, large columnar dendritic crystals typical of directional solidification, and untextured, equiaxed, ‘fine-grained’ crystals that can result from diffusion creep. We also studied the wavelength/grain size dependence of scattering for these two microstructures. We used a Zn-rich Sn alloy not because we expect it to have intrinsic attenuation similar to Fe under inner core conditions, but because its hcp crystal structure is the likely phase of the Fe alloy in the inner core, making it suitable for understanding the role of microstructure on scattering in the inner core. For the purpose of scaling the experiments to the inner core, pressure and temperature affect scattering primarily through their effects on the elastic constants of Fe and inner core growth dynamics, both of which we account for.
We developed an algorithm using the pulse-echo technique to experimentally determine a scattering quality factor QZ. We set criteria to determine, and measured, the energy per cycle in the first echo T1, which is a measure of the transmitted energy, and the energy per cycle that is reflected before the first echo R1, which represents the scattered energy. In order to facilitate comparison with seismic quality factors we defined a scattering quality factor QZ= (R1+ T1)/R1. Scaling QZ from the laboratory experiments to the inner core depends on the magnitude of the single-crystal wave speed anisotropy, which is known for Zn, but uncertain for Fe under inner core conditions, so we scaled the experimental results for single-crystal Fe elastic anisotropy between 5 and 20 %.
As expected, we found a directionally solidified microstructure has a highly anisotropic QZ, showing almost no scattering in the growth direction, whereas in the transverse directions scattering attenuation in the inner core may be comparable to intrinsic attenuation. Taking into account the anisotropy factor for scattering in polycrystalline, anisotropic material, our results predict randomly oriented, equiaxed 10 km-sized grains in the inner core would exhibit more scattering attenuation that the total inferred seismic attenuation, ruling out such a microstr
{"title":"An experimental ultrasonic method to determine a scattering quality factor, with application to earth's inner core","authors":"Ming Gong , Michael I. Bergman","doi":"10.1016/j.pepi.2025.107456","DOIUrl":"10.1016/j.pepi.2025.107456","url":null,"abstract":"<div><div>Seismic attenuation can be intrinsic or due to scattering. The relative role of each for Earth's inner core is uncertain. Whereas intrinsic attenuation depends primarily on the material, temperature, and pressure, scattering is primarily a function of microstructure, that is, grain size, shape, texture, as well as single-crystal elastic anisotropy. Here we studied experimentally scattering of ultrasonic compressional waves in a hexagonal close-packed (hcp) Zn-rich Sn alloy, for two microstructures that are likely relevant to the inner core: textured, large columnar dendritic crystals typical of directional solidification, and untextured, equiaxed, ‘fine-grained’ crystals that can result from diffusion creep. We also studied the wavelength/grain size dependence of scattering for these two microstructures. We used a Zn-rich Sn alloy not because we expect it to have intrinsic attenuation similar to Fe under inner core conditions, but because its hcp crystal structure is the likely phase of the Fe alloy in the inner core, making it suitable for understanding the role of microstructure on scattering in the inner core. For the purpose of scaling the experiments to the inner core, pressure and temperature affect scattering primarily through their effects on the elastic constants of Fe and inner core growth dynamics, both of which we account for.</div><div>We developed an algorithm using the pulse-echo technique to experimentally determine a scattering quality factor <em>Q</em><sub><em>Z</em></sub>. We set criteria to determine, and measured, the energy per cycle in the first echo <em>T</em><sub><em>1</em></sub>, which is a measure of the transmitted energy, and the energy per cycle that is reflected before the first echo <em>R</em><sub><em>1</em></sub>, which represents the scattered energy. In order to facilitate comparison with seismic quality factors we defined a scattering quality factor <em>Q</em><sub><em>Z</em></sub> <em>= (R</em><sub><em>1</em></sub> <em>+ T</em><sub><em>1</em></sub><em>)/R</em><sub><em>1</em></sub>. Scaling <em>Q</em><sub><em>Z</em></sub> from the laboratory experiments to the inner core depends on the magnitude of the single-crystal wave speed anisotropy, which is known for Zn, but uncertain for Fe under inner core conditions, so we scaled the experimental results for single-crystal Fe elastic anisotropy between 5 and 20 %.</div><div>As expected, we found a directionally solidified microstructure has a highly anisotropic <em>Q</em><sub><em>Z</em></sub>, showing almost no scattering in the growth direction, whereas in the transverse directions scattering attenuation in the inner core may be comparable to intrinsic attenuation. Taking into account the anisotropy factor for scattering in polycrystalline, anisotropic material, our results predict randomly oriented, equiaxed 10 km-sized grains in the inner core would exhibit more scattering attenuation that the total inferred seismic attenuation, ruling out such a microstr","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107456"},"PeriodicalIF":1.9,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221139","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}
Pub Date : 2025-09-22DOI: 10.1016/j.pepi.2025.107453
C. Beghein , J. Li
The largest seismic event ever detected on Mars occurred on May 4, 2022, likely situated just north of the hemispherical dichotomy, east of the landing site, and south of Cerberus Fossae. This event was unique in that it generated both Love and Rayleigh waves, including fundamental and higher modes, providing us with a rare opportunity to determine whether seismic radial anisotropy is present on Mars. We performed non-linear waveform modeling and used a Niching Genetic Algorithm to find acceptable velocity models. Our analysis revealed that seismic anisotropy is necessary in the top 40 km, with the fast direction for seismic wave propagation being horizontal, similar to previous results solely based on fundamental mode surface wave group velocity dispersion. Our new models display layering with varying degrees of anisotropy. We found anisotropic parameter ξ = 1.0-1.2 between 5 and 20 km depth and ξ = 1.2-1.3 at 25–30 km depth. No significant anisotropy was detected below 35 km. While the origin of the anisotropy is still being debated, it is characteristic of a medium with a vertical symmetry axis and could result from both magmatic events and impacts. We propose that the anisotropy layering reflects different stages in the formation history of the Martian crust.
{"title":"Seismic anisotropy layering in the Martian lowlands crust","authors":"C. Beghein , J. Li","doi":"10.1016/j.pepi.2025.107453","DOIUrl":"10.1016/j.pepi.2025.107453","url":null,"abstract":"<div><div>The largest seismic event ever detected on Mars occurred on May 4, 2022, likely situated just north of the hemispherical dichotomy, east of the landing site, and south of Cerberus Fossae. This event was unique in that it generated both Love and Rayleigh waves, including fundamental and higher modes, providing us with a rare opportunity to determine whether seismic radial anisotropy is present on Mars. We performed non-linear waveform modeling and used a Niching Genetic Algorithm to find acceptable velocity models. Our analysis revealed that seismic anisotropy is necessary in the top 40 km, with the fast direction for seismic wave propagation being horizontal, similar to previous results solely based on fundamental mode surface wave group velocity dispersion. Our new models display layering with varying degrees of anisotropy. We found anisotropic parameter <em>ξ</em> = 1.0-1.2 between 5 and 20 km depth and <em>ξ</em> = 1.2-1.3 at 25–30 km depth. No significant anisotropy was detected below 35 km. While the origin of the anisotropy is still being debated, it is characteristic of a medium with a vertical symmetry axis and could result from both magmatic events and impacts. We propose that the anisotropy layering reflects different stages in the formation history of the Martian crust.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"368 ","pages":"Article 107453"},"PeriodicalIF":1.9,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145158427","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}
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