Physics of the Earth and Planetary Interiors最新文献

{"title":"Core-surface kinematic control of polarity reversals in advanced geodynamo simulations","authors":"Julien Aubert,&nbsp;Maylis Landeau,&nbsp;Alexandre Fournier,&nbsp;Thomas Gastine","doi":"10.1016/j.pepi.2025.107365","DOIUrl":"10.1016/j.pepi.2025.107365","url":null,"abstract":"<div><div>The geomagnetic field has undergone hundreds of polarity reversals over Earth's history, at a variable pace. In numerical models of Earth's core dynamics, reversals occur with increasing frequency when the convective forcing is increased past a critical level. This transition has previously been related to the influence of inertia in the force balance. Because this force is subdominant in Earth's core, concerns have been raised regarding the geophysical applicability of this paradigm. Reproducing the reversal rate of the past million years also requires forcing conditions that do not guarantee that the rest of the geomagnetic variation spectrum is reproduced. These issues motivate the search for alternative reversal mechanisms. Using a suite of numerical models where buoyancy is provided at the bottom of the core by inner-core freezing, we show that the magnetic dipole amplitude is controlled by the relative strength of subsurface upwellings and horizontal circulation at the core surface. A relative weakening of upwellings brings the system from a stable to a reversing dipole state. This mechanism is purely kinematic because it operates irrespectively of the interior force balance. It is therefore expected to apply at the physical conditions of Earth's core. Subsurface upwellings may be impeded by stable stratification in the outermost core. We show that with weak stratification levels corresponding to a nearly adiabatic core surface heat flow, a single model reproduces the observed geomagnetic variations ranging from decades to millions of years. In contrast with the existing paradigm, reversals caused by this stable top core mechanism become more frequent when the level of stratification increases i.e. when the core heat flow decreases. This suggests that the link between mantle dynamics and magnetic reversal frequency needs to be reexamined.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"364 ","pages":"Article 107365"},"PeriodicalIF":2.4,"publicationDate":"2025-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143942898","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}

{"title":"Crustal shear-wave velocity structure of the Namche Barwa massif, eastern Himalayan Syntaxis, Tibet from ambient noise tomography","authors":"Jiawei Tan ,&nbsp;Xuzhang Shen ,&nbsp;Siyuan Cheng ,&nbsp;Rui Gao ,&nbsp;Wentian Wang","doi":"10.1016/j.pepi.2025.107363","DOIUrl":"10.1016/j.pepi.2025.107363","url":null,"abstract":"<div><div>The eastern termination of the Himalayan orogeny, known as Namche Barwa, serves as a crucial natural laboratory for geodynamic studies of the Tibetan Plateau due to its distinctive geological and geomorphological characteristics. To enhance the understanding of regional tectonics, we deployed a dense array of 374 short-period geophones from June to July 2020 to record continuous waveforms. Using vertical-component data, we computed cross-correlation functions and extracted 13,466 Rayleigh wave phase-velocity dispersion curves for periods ranging from 0.8 to 8 s. We applied the direct surface wave tomography method to invert the three-dimensional shear-wave velocity structure at depths of 0–6 km in the region. Our results reveal that the shallow crustal velocity structure in this region exhibits significant lateral heterogeneity, reflecting the complexity of the geological units. Low-velocity anomalies are primarily observed near faults, including the Indus-Yarlung Suture Zone and the Jiali Fault, while a high-velocity anomaly is detected beneath the Namche Barwa massif. In combination with previous geophysical studies, including magnetotelluric (MT) and seismic imaging results, this high-velocity anomaly is speculated to reflect the intrusion of deep crustal material into the shallow crust. The spatial correlation between the velocity model and seismicity distribution suggests that earthquakes are closely associated with local stress conditions, velocity structure, and the presence of aqueous fluids and geothermal anomalies.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"363 ","pages":"Article 107363"},"PeriodicalIF":2.4,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143858721","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}

{"title":"Variations in mantle flow beneath the Eastern Himalaya inferred from shear wave splitting","authors":"Arti Devi ,&nbsp;Sunil K. Roy ,&nbsp;Jyotima Kanaujia ,&nbsp;Venkatesh Vempati ,&nbsp;M. Ravi Kumar","doi":"10.1016/j.pepi.2025.107364","DOIUrl":"10.1016/j.pepi.2025.107364","url":null,"abstract":"<div><div>This study attempts to understand the upper mantle deformation patterns beneath the Eastern Himalaya by performing shear wave splitting analysis of core-refracted phases. Out of the 83 broadband seismic stations used, data from 70 stations are analysed for the first time. This includes 21 stations which were newly deployed along two profiles in Arunachal Himalaya, to fill the gaps in the stations used for previous studies. In total, 172 well constrained new splitting and 215 null measurements are obtained in this study. Average delay time values of 0.64 and 0.76 s in the Bhutan and Arunachal Himalaya respectively, suggest weak anisotropy, probably due to a steep subduction of the Indian mantle lithosphere. There is a systematic variation in the orientation of fast polarization azimuths in the western (Bhutan Himalaya and western part of Arunachal Himalaya) and eastern segments (central to the eastern part of Arunachal Himalaya). In both these segments, the orientation of fast polarization azimuths varies dominantly from N<em>E</em>-SW or/and ENE-WSW, to E-W, from west to east. In the western and central parts of Bhutan Himalaya, the influence of absolute plate motion related strain in the asthenospheric mantle cannot be ruled out, while in its eastern part and Arunachal Himalaya, the azimuthal anisotropy can be explained by arc parallel mantle flow due to slab rollback. In addition, a few observations in the central part of Arunachal Himalaya indicate a slightly larger delay time, along NNE-SSW, which could be associated with mantle wedge flow. The eastern part of Arunachal Himalaya might be associated with a repulsive arc parallel flow from the Arunachal and Burmese arcs, resulting in null measurements. The optimal depth of anisotropy in Bhutan and Arunachal Himalaya is around <span><math><mn>220</mn><mo>−</mo><mn>270</mn></math></span> and <span><math><mn>200</mn><mo>−</mo><mn>240</mn></math></span> km respectively, suggesting that the source of anisotropy lies in the upper part of the asthenosphere.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"363 ","pages":"Article 107364"},"PeriodicalIF":2.4,"publicationDate":"2025-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143858749","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}

{"title":"Spatial variation of crustal anisotropy in Simeulue Island, Indonesia, from shear wave splitting analysis","authors":"Syuhada Syuhada ,&nbsp;Faiz Muttaqy ,&nbsp;Titi Anggono ,&nbsp;Bayu Pranata ,&nbsp;Nanang T. Puspito ,&nbsp;Mohamad Ramdhan ,&nbsp;Febty Febriani ,&nbsp;Muhammad Ma'ruf Mukti ,&nbsp;Cinantya Nirmala Dewi ,&nbsp;Mohammad Hasib ,&nbsp;Aditya Dwi Prasetio ,&nbsp;Atin Nur Aulia ,&nbsp;Ade Surya Putra","doi":"10.1016/j.pepi.2025.107362","DOIUrl":"10.1016/j.pepi.2025.107362","url":null,"abstract":"<div><div>Simeulue Island sits near the northern subduction margin of the Sumatran Megathrust, which is characterized by high tectonic activities and earthquakes. The oblique subduction along this margin has developed a complicated crustal deformation on the island, including faulting, uplifting and crustal segmentation. In the subduction zone, crustal anisotropy is often caused by stress-induced anisotropy in which the anisotropy direction is parallel to the stress direction. However, the complex crustal structure around the study area may produce a complicated anisotropy pattern. Here, we measure crustal seismic anisotropy from shear wave splitting analysis using the seismic data recorded at eight temporary stations spread across Simeulue Island. We apply the 2-D tomographic inversion and spatial averaging technique to map the splitting anisotropy patterns around the region. This research allows us to gain new insight into the crustal deformation pattern and its relationship with the complicated crustal structure beneath the island. The splitting result shows variations of anisotropy pattern around the study area. The spatially averaged fast directions at the northern region are trench-parallel, consistent with the strike of the geological features resulting from the strain partitioning deformation of the oblique convergence. Higher strength anisotropy is also observed in this area, indicating that the local fault system may strongly contribute to the crustal anisotropy. In the southern part of the island, the spatial averaging of fast direction gives a consistent pattern with the maximum regional stress direction, suggesting that anisotropy is mainly associated with stress-aligned microcracks. The central part of the island exhibits different splitting directions, marking the boundary of the geological structures between the areas in the north and south of the island. This pattern is also accompanied by high-strength anisotropy, suggesting that the source may be associated with the subducting geological structures beneath the area playing a significant role in the rupture barrier of the great events, as suggested by several previous studies.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"363 ","pages":"Article 107362"},"PeriodicalIF":2.4,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850608","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}

{"title":"Seismotectonics of the Gulf of Gökova, Southwest Anatolia, using double-difference seismic tomography, earthquake relocation, and moment tensor solutions: The 20 July 2017 Mw6.5 Bodrum-Kos earthquake","authors":"Tuğba Özdemirli-Esat ,&nbsp;Melike Doğanay-Özkan ,&nbsp;Korhan Esat","doi":"10.1016/j.pepi.2025.107361","DOIUrl":"10.1016/j.pepi.2025.107361","url":null,"abstract":"<div><div>The 20 July 2017 Mw6.5 Bodrum-Kos main shock that occurred in the Gulf of Gökova is one of the largest earthquakes in the north-south extensional Aegean region. In this study, we generated the first three-dimensional local earthquake tomography model for the Gökova region using the double-difference tomography algorithm to provide a contribution to discussions on the source fault of the main shock. The 2500 earthquake records of magnitude ≥2.3 between 01 January 2017 and 31 December 2017 were chosen from the 19 strong-motion accelerometer and 11 weak-motion seismometer stations. The P- and S-wave velocity models and Vp/Vs ratio model of the study area were created, and 1488 earthquakes were relocated. With the help of seismic tomographic imaging, we concluded that the main shock occurred on the south-dipping Gökova Fault Zone, not on the north-dipping fault plane suggested in some studies. We also determined that some earthquakes that occurred in 2017 were associated with a north-dipping normal fault observed down to 10 km depth immediately north of the Gökova Fault Zone. Additionally, the Datça-Kale Main Breakaway Fault, which separates the sedimentary cover and the basement rocks, was also determined in the tomographic profiles. The kinematic analysis of moment tensor solutions of 64 earthquakes, mostly with magnitudes greater than 4, is consistent with the north-south extensional tectonic regime in the Aegean region.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"364 ","pages":"Article 107361"},"PeriodicalIF":2.4,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143907705","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}

{"title":"Corrigendum to “Lithospheric structure beneath the Upper Indus Basin and its adjacent regions from inversion of surface wave dispersion” [Physics of the Earth and Planetary Interiors Volume 362, May 2025, 107345]","authors":"Deepak Kumar ,&nbsp;G. Suresh ,&nbsp;M.L. Sharma ,&nbsp;Siddharth Dey ,&nbsp;S.C. Gupta","doi":"10.1016/j.pepi.2025.107353","DOIUrl":"10.1016/j.pepi.2025.107353","url":null,"abstract":"","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"365 ","pages":"Article 107353"},"PeriodicalIF":2.4,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144241633","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}

{"title":"The history of geomagnetic secular variation hemispherical dichotomies","authors":"Mathis Colas,&nbsp;Filipe Terra-Nova,&nbsp;Hagay Amit","doi":"10.1016/j.pepi.2025.107352","DOIUrl":"10.1016/j.pepi.2025.107352","url":null,"abstract":"<div><div>Monitoring the geomagnetic field and its secular variation (SV) is essential for understanding the Earth's internal dynamics. In particular, the SV provides an image of the geodynamo at the top of the core. However, the SV is not available for paleomagnetic field models. Here, we propose a new index for assessing the paleomagnetic SV. This new index is based on the well-established inverse linear relationship between the SV timescales and the degree of spherical harmonics. We demonstrate using the historical field where the SV is available that this index adequately captures the large-scale features of the true SV, in particular the SV Atlantic/Pacific and North/South dichotomies. The recovery of these SV hemispherical dichotomies by our proposed index does not deteriorate from truncated fields at spherical harmonics degree 14 to 5. Applied to a paleomagnetic field model for the past 100 kyr, we find a persistent SV dichotomy between the quiet Pacific and active Atlantic hemispheres, consistent with heterogeneous inner core freezing. In addition, according to our index, a persistent stronger SV prevails at the northern hemisphere, which is the case at the present day due to a fast westward jet at high latitudes of the northern hemisphere.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"363 ","pages":"Article 107352"},"PeriodicalIF":2.4,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143844796","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}

{"title":"Electrical and thermal conductivities of Fe–Ni–Si alloy under core conditions: A reevaluation","authors":"Kenji Ohta ,&nbsp;Hayato Inoue ,&nbsp;Sho Suehiro ,&nbsp;Kei Hirose ,&nbsp;Saori Kawaguchi-Imada ,&nbsp;Haruhiko Dekura","doi":"10.1016/j.pepi.2025.107351","DOIUrl":"10.1016/j.pepi.2025.107351","url":null,"abstract":"<div><div>We present experimental results on the electrical resistivity (the inverse of electrical conductivity) of solid hexagonal close-packed (hcp) and liquid Fe–10 at.% Ni–22.5 at.% Si (Fe–11.8 wt% Ni–12.7 wt% Si) alloys under high-pressure and high-temperature conditions, corresponding to the Earth's outer core conditions, using a diamond anvil cell. We found minimal temperature dependence of the resistivity of the hcp Fe–Ni–Si alloy, indicating thermochemically-induced resistivity saturation. We also observed that the resistivity saturation reduced the extent of resistivity change during the melting transition. Based on our findings, we estimate an upper limit for the core resistivity of approximately 110 μΩcm (= 1.10 × 10⁻⁶ Ωm) at the top of the outer core, corresponding to a lower limit for the electrical and thermal conductivities of approximately 9.2 × 10⁵ Sm⁻¹ and 90 Wm⁻¹ K⁻¹, respectively. Such high core conductivity is unavoidable and must be accounted for in understanding the Earth's thermal evolution.</div><div><em>“Extrapolation to core conditions of laboratory observations of electrical resistivities of iron and its alloys has been hampered by lack of understanding of interactions between the effects of temperature, pressure and impurities.”—F. D. Stacey and O.</em> L. <em>Anderson (2001).</em></div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"363 ","pages":"Article 107351"},"PeriodicalIF":2.4,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143835261","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}

{"title":"Lithospheric structure beneath the Upper Indus Basin and its adjacent regions from inversion of surface wave dispersion","authors":"Deepak Kumar ,&nbsp;G. Suresh ,&nbsp;M.L. Sharma ,&nbsp;Siddharth Dey ,&nbsp;S.C. Gupta","doi":"10.1016/j.pepi.2025.107345","DOIUrl":"10.1016/j.pepi.2025.107345","url":null,"abstract":"<div><div>We propose an enhanced model of the crust and upper mantle structure beneath the Upper Indus Basin, derived from the combined inversion of Rayleigh and Love wave group velocity dispersion data from 164 seismic events recorded by 58 stations, covering periods from 4 to 100 s. By using the Genetic Algorithm approach within this joint inversion process, we developed a detailed shear wave velocity model for the region. The earthquakes were categorized into three clusters based on their epicentral locations, allowing for a detailed analysis beneath the western, central, and eastern segments of the Upper Indus Basin. The analysis shows a gradual increase in crustal thickness from the west to the east, with an average thickness of ∼61.8 km and a shear wave velocity ∼ 4.6 km/s. The Lithosphere-Asthenosphere Boundary (LAB) is identified at a depth of 160 km, indicated by a velocity decrease of about 1.6 %. Our results also reveal a sedimentary cover of ∼4 km and we postulate a felsic crust similar to southern Pamir, which could have resulted from the loss of mafic lower crust by lithospheric delamination or foundering due to gravitational instability. We state the absence of mid-crustal low velocity layer within the Basin and also discard the possibility of any requirement for radial anisotropy, based on the adequate fit of Rayleigh and Love the dispersion data with minimal uncertainty. The study provides a significant refinement of the crustal and upper mantle structure of the Upper Indus Basin, contributing valuable insights into regional tectonics.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"362 ","pages":"Article 107345"},"PeriodicalIF":2.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143725250","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}

{"title":"Shared periodicities between the length of day and the geomagnetic field at millennial timescales","authors":"M. Puente-Borque ,&nbsp;F.J. Pavón-Carrasco ,&nbsp;S.A. Campuzano ,&nbsp;A. González-López ,&nbsp;M. Folgueira ,&nbsp;M.L. Osete","doi":"10.1016/j.pepi.2025.107350","DOIUrl":"10.1016/j.pepi.2025.107350","url":null,"abstract":"<div><div>The dynamics of Earth's outer core control the geomagnetic field and produce variations in the length of day (LOD). This phenomenon has been extensively studied at decadal and interannual scales but is still little known on the millennial timescale. Reconstructed variations in the length of day from ancient records of eclipses exhibit an oscillating component with a millennial period that cannot be explained by tidal effects, glacial isostatic adjustment or the ocean and atmospheric dynamics. In this work, frequency analysis and correlation techniques have been applied to LOD variations and to the dipole and quadrupole geomagnetic field provided by paleomagnetic reconstructions. We found that the non-tidal fluctuations of the LOD are correlated with the paleosecular variation of the Earth's magnetic field over the last three millennia. In particular, LOD maxima occur when the eccentric dipole shifts towards the Pacific region and the geocentric dipole becomes more axial, and LOD minima correspond to a more centred eccentric dipole and a more tilted geocentric dipole towards Atlantic region. These results provide new information about the coupling between the Earth's rotation and the paleosecular variation of the geomagnetic field on millennial time scales.</div></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"362 ","pages":"Article 107350"},"PeriodicalIF":2.4,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143768158","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}