Physics of the Earth and Planetary Interiors最新文献

{"title":"Strain localization by diffusion creep of Bridgmanite-Ferropericlase mixture: Application of self-consistent method","authors":"H.E. Cho ,&nbsp;Shun-ichiro Karato","doi":"10.1016/j.pepi.2024.107224","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107224","url":null,"abstract":"<div><p>In this study, we investigate the finite deformation of a polycrystalline mixture of bridgmanite (Br) and ferropericlase (Fp) by diffusion creep at the lower mantle-like temperature and pressure by using the self-consistent approach. We explore the influence of volume fraction of Fp, viscosity contrast, and strain dependence (effect of shape change) under both axial (coaxial deformation) and simple shear (non-coaxial deformation). Our present study shows: i) the strength (viscosity) contrast between Fp and Br increases with strain since the viscosity of Fp significantly decreases as Fp grain elongates, and (ii) deformation starts from nearly homogeneous strain to finally nearly homogeneous stress under simple shear whereas deformation behavior remains nearly homogeneous strain under axial deformation. A more substantial creep rate partitioning occurs in simple shear than in axial deformation. These results imply that strain localization <em>via</em> diffusion creep might occur in the lower mantle, particularly in regions where the simple shear is dominated (<em>i.e.</em>, in the boundary layers (<em>e.g.</em>, the D″ layer)).</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107224"},"PeriodicalIF":2.4,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141483834","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":"Enigmatic mixture of magnetite magnetofossils and diagenetic greigite as the magnetic carriers of the Early Miocene lacustrine sediments from the Most Basin in Central Europe","authors":"Hakan Ucar ,&nbsp;Gunther Kletetschka ,&nbsp;Ramon Egli ,&nbsp;Karel Mach ,&nbsp;Michael S. Petronis ,&nbsp;Hana Grison ,&nbsp;Stephanie Scheidt ,&nbsp;Petr Schnabl ,&nbsp;Simon Kdyr","doi":"10.1016/j.pepi.2024.107216","DOIUrl":"10.1016/j.pepi.2024.107216","url":null,"abstract":"<div><p>The Early Miocene lacustrine sediments of the Most Basin in the Czech Republic preserve a European continental paleoenvironmental archive. A number of paleoenvironmental and magnetostratigraphic studies have been carried out on sediment cores from boreholes due to ongoing coal mining in the basin. However, the magnetic carriers of the studied sediments have not been identified clearly. Here, we present a detailed paleo-rock magnetic study from the Burdigalian sediments near the Bilina mining area, Most Basin. The studied clay sediments cover the period of local lakes and a basin-wide lake above the main coal seam. Our results suggest that the magnetic carriers of the studied section in the Most Basin are mixtures of authigenic greigite and magnetite magnetofossils with overlapping magnetic signatures. Greigite is formed by migration of pore water through the sediment column, where iron from siderite grains reacts with these fluids with limited H₂S, which then favors greigite precipitation. The co-existence of greigite and magnetite indicates a partial dissolution of magnetofossils due to H₂S deficiency. Diagenetic greigite has been problematic in paleomagnetic studies due to an unknown time lag between the depositional remanence and the chemical remanent magnetization (CRM). A ghost polarity interval reveals that greigite acquired at least ∼45 kyr delayed CRM. The revealed timing of remanence acquisition brings a new perspective to the chronostratigraphic structure of the Most Basin.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107216"},"PeriodicalIF":2.4,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141393963","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":"Quantifying the features of earthquake clusters in north-Central Iran, based on nearest-neighbor distances and network analysis","authors":"Mohammad Talebi ,&nbsp;Mehdi Zare ,&nbsp;Antonella Peresan","doi":"10.1016/j.pepi.2024.107215","DOIUrl":"10.1016/j.pepi.2024.107215","url":null,"abstract":"<div><p>The statistical features of earthquake clusters in North-Central Iran (Tehran Region) are investigated, with the aim of quantitatively characterizing the properties of earthquake triggering and allow exploring their possible relations with the tectonic setting of the study area.</p><p>The nearest-neighbor approach is used for the identification of the earthquake clusters in the space-time-energy domain. This approach permits for a data-driven identification of clusters so that, within multi-event clusters, the features of secondary and higher orders dependent events can be explored. The study is based on a revised dataset that is extracted from the catalog compiled by the Iranian Seismological Center (IRSC) for the period of 1996–2022. In order to exclude the effect of non-tectonic events, which turn out quite numerous within the study region, explosions within quarry-rich areas are removed; the identification of non-tectonic events is performed by considering the normalized ratios of daytime to nighttime events in an iterative removal procedure. According to preliminary analysis of the resulting catalog, an area is selected, within which a satisfactory completeness level is assessed for events with magnitude &gt;2.0. Robust values of the scaling parameters, namely the b-value and the fractal dimension of epicenters, are also computed and are used to calculate the nearest-neighbor distances and to identify the earthquake clusters.</p><p>The nearest-neighbor method also permits to investigate the internal structure of earthquake sequences, and to differentiate the spatial properties of seismicity according to the different topological features of the clusters structure. The obtained results allow us identifying two macro-areas, approximately separated by the 52°E meridian, which are characterized by different clustering features, namely: high complexity indexes, indicating simple (burst-like) structure of clusters, to the East; low complexity index, corresponding to complex multi-level (swarm-like) structure of clusters, to the West. The complexity measures, borrowed from network theory (i.e. the Closeness and Outdegree Centralization indexes), consistently capture the complexity of the identified clusters, and confirm that the cluster structures have distinct preferred geographic locations. The territorial heterogeneity of the examined clustering properties can be related with the spatial variability of tectonic, structural and geophysical features of the Alborz region, in good agreement with findings from the Alps-Dinarides junction (Northeastern Italy), a region also characterized by a contractional structural setting, mainly including reverse and strike-slip faulting systems, and by moderate to high seismic activity.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107215"},"PeriodicalIF":2.3,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141282201","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":"Evolution and disappearance of the paleo-West Pacific Anomaly: Implications to the future of South Atlantic Anomaly","authors":"Yaochen Yue ,&nbsp;Jiawei Gao ,&nbsp;Fei He ,&nbsp;Yong Wei ,&nbsp;Shuhui Cai ,&nbsp;Huapei Wang ,&nbsp;Yuqi Wang ,&nbsp;Zhaojin Rong ,&nbsp;Zhonghua Yao ,&nbsp;Wei Lin ,&nbsp;Yongxin Pan","doi":"10.1016/j.pepi.2024.107214","DOIUrl":"10.1016/j.pepi.2024.107214","url":null,"abstract":"<div><p>Palaeomagnetic and modern geomagnetic measurements indicate that the South Atlantic Anomaly (SAA) has undergone rapid changes over the past few hundred years. Its minimum intensity decreased at an average rate of 26 not yr⁻¹, accompanied by a continuous westward drift and spatial expansion. Recently, a secondary minimum of SAA emerged near southern Africa, leading to speculation that expansion of the SAA could indicate an impending geomagnetic reversal. Here, we focus on the evolution and disappearance of the paleo-West Pacific Anomaly (WPA), as another SAA-like structure, which may have implications for the future of SAA evolution. We regard the WPA as SAA-like due to its feature and its association with a reversal flux patch on the core-mantle boundary. Consequently, we suggest that the observed evolutionary pattern in the WPA can serve as a reference for other negative anomalies, such as the SAA. By analysing models that combine datasets of archaeomagnetic and historical records, such as gufm1 and HistKalmag, it is found that the WPA occurred between 1600 and 1820 CE. Over its duration, the WPA experienced phases of rapid expansion, drift, and division. Eventually, its primary component faded away, giving rise to a new segment that continued to expand. The initial two evolutionary phases of the WPA are similar to the evolution of the SAA over the past century. According to the WPA's evolution, it suggests that the current state of the SAA may correspond to an early stage of splitting. Forecasts based on the evolution of the WPA indicate a rapid expansion of the anomalous region in the short term, followed by a gradual reduction in its primary component and continued expansion of a new local minimum. This study provides valuable insight into the evolution of the SAA and highlights the potential utility of the WPA as an evolutionary reference for such geomagnetic phenomena.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107214"},"PeriodicalIF":2.3,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141276684","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":"A 3D computational model for ground motion simulation in Peninsular India","authors":"K.P. Sreejaya,&nbsp;S.T.G. Raghukanth","doi":"10.1016/j.pepi.2024.107208","DOIUrl":"https://doi.org/10.1016/j.pepi.2024.107208","url":null,"abstract":"<div><p>Due to the gradual and constant accumulation of seismic energy, Peninsular India (PI) is typically considered seismically stable with low to moderate seismicity. The seismic studies in Peninsular India always resorted to synthetic ground motion simulations, because of the limited instrumentation and hence lack of recorded data. In the absence of a well-defined medium model for PI, the usual practice is to use simple site proxies or one-dimensional velocity structures for ground motion simulations. However, the region consists of multi-scale geometric complexities, significant topography, and sedimentary basins and is surrounded by deep oceans. Thus, the radiated seismic wave field in the region is influenced by the medium properties and in the absence of a well-defined tomography model the reliable estimation of seismic hazard is a challenging problem in PI. Therefore, the seismic wave propagation in PI can be investigated using numerical simulation with reliable 3D computational model for PI, incorporating the knowledge of the underlying Earth structure. Hence, the present study attempts to develop a sophisticated three-dimensional (3D) medium model of Peninsular India for physics-based ground motion simulations for regional earthquakes. This is aided by the availability of one-dimensional (1D) velocity models and the crustal structure from the receiver function analysis which provides valuable insight into the variation of material properties in the region. In the present study, &gt;100 s of 1D velocity profiles are collected from various literature, which is then grouped under 23 different geological regions identified in PI (as per GSI (2000)). The averaged material properties are assigned per each geological region and the information on sediment depths, basin geometry, topography, and bathymetry are incorporated. We use the spectral element method (SEM) to calibrate our 3D computational model by simulating synthetic seismograms and comparing them to recorded ground motions for two past earthquakes: the 2001 Mw 7.6 Bhuj earthquake and the 1997 Mw 5.8 Jabalpur earthquake. Further, the seismic waveforms at the near field of 2001 Mw 7.6 Bhuj event are simulated using a refined regional model. The spatial variability of associated seismic intensities and peak ground velocity (PGV) amplification are investigated. In addition, a study of the impact of model depth truncation and sphericity on ground motion is also conducted. The implemented medium model is the first of its kind for Peninsular India and can reliably be used in seismic wave propagation studies in the region. The simulated outcomes from the model are of engineering importance as these results can be used for seismic hazard assessment of the region.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107208"},"PeriodicalIF":2.3,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141312777","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":"Lateral electrical conductivity variations along the Main Himalayan thrust in the northwestern Himalayas: Insights from 3D Magnetotelluric forward modeling","authors":"S. Dhamodharan ,&nbsp;Khasi Raju ,&nbsp;Prasanta K. Patro","doi":"10.1016/j.pepi.2024.107213","DOIUrl":"10.1016/j.pepi.2024.107213","url":null,"abstract":"<div><p>Understanding the arc parallel variation on the geometry of the Main Himalayan Thrust (MHT) is as important as understanding the arc perpendicular variation in the Himalayas. The geometric variability of the MHT holds significant implications for the occurrence of major and great earthquakes. Three-dimensional magnetotelluric (MT) forward modeling enables the investigation of potential crustal models along the MHT in northwest Himalayas. MT impedance tensors were computed utilizing the 3D forward modeling code MTD3FWD. Previously established MT resistivity and seismic velocity models from various sectors of the northwestern Himalayas were employed as inputs for generating the resistivity mesh necessary for 3D forward modeling. The computed impedance tensors by 3D forward computation were cross-referenced with the original published MT data to validate their accuracy. A lateral resistivity cross section is also derived from the 3D forward model along the sub-Himalaya and lesser-Himalaya region to study the lateral heterogeneity. The lateral resistivity cross-section reveals significant heterogeneity within the crust, marked by both high and low-resistive structures and a possible lateral ramp along the MHT. The geometry of the lateral MHT showcases a gradual incline within the Himachal sector and a steep ramp within the Garhwal and Kumaun sectors in the northwestern Himalayas. The crustal architecture exhibits distinct nearly-vertical resistive and conductive features beneath the study area. Consequently, the crust within this region is characterized by considerable heterogeneity, influenced by a network of subsurface faults and ridges. The Delhi Haridwar Ridge, which exhibits high resistivity, plays a significant role in dictating the lateral dip of the MHT and exerting control over seismic activity patterns in the region.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"353 ","pages":"Article 107213"},"PeriodicalIF":2.3,"publicationDate":"2024-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141139033","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":"Seismic evidence for possible entrainment of rising plumes by subducting slab induced flow in three subduction zones surrounding the Caribbean Plate","authors":"Morvarid Saki ,&nbsp;Sara Aniko Wirp ,&nbsp;Magali Billen ,&nbsp;Christine Thomas","doi":"10.1016/j.pepi.2024.107212","DOIUrl":"10.1016/j.pepi.2024.107212","url":null,"abstract":"<div><p>The dynamic processes associated with subducting tectonic plates and rising plumes of hot material are typically treated separately in dynamical models and seismological studies. However, various types of observations and related models indicate these processes overlap spatially. Here we use precursors to PP and SS reflecting off mantle transition zone discontinuities to map deflections of these discontinuities near three subduction zones surrounding the Caribbean Plate: 1) Lesser Antilles, 2) Middle America and 3) northern South American subduction zones. In all three regions slow seismic anomalies are present behind the sinking slab within the transition zone in tomographic images. Using array methods, we identify precursors and verify their in-plane propagation for M_W ≥ 5.8 events occurring between the years 2000 and 2020 by generating a large number of source receiver combinations with reflection points in the area, including crossing ray paths. The measured time lag between PP/SS arrivals and their corresponding precursors on robust stacks are used to measure the depth of the mantle transition zone discontinuities. In all three areas we find evidence for upward deflection of the 660 discontinuity behind the sinking slab, consistent with the presence of hot plume material (average temperature anomalies of 180 to 620 K), while there is not a corresponding downward deflection of the 410 km discontinuity. One interpretation of these disparate observations is suggested based on comparison to existing models of mantle convection and subduction: plume material rising across 660 km discontinuity could be entrained by lateral flow in the transition zone induced by the nearby sinking slab, and thus delaying the rise of hot material across the 410 km discontinuity.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"352 ","pages":"Article 107212"},"PeriodicalIF":2.3,"publicationDate":"2024-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0031920124000700/pdfft?md5=f75837acafbb78dc85c551a3a064f091&pid=1-s2.0-S0031920124000700-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141055267","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}

{"title":"Spatial variation of body wave attenuation in Garhwal-Kumaun Himalaya region, India","authors":"Rahul Biswas,&nbsp;Prantik Mandal,&nbsp;Satish Saha,&nbsp;Raju Prathigadapa,&nbsp;M. Shekar,&nbsp;R. Vijaya Raghavan","doi":"10.1016/j.pepi.2024.107211","DOIUrl":"10.1016/j.pepi.2024.107211","url":null,"abstract":"<div><p>We have investigated the spatial variation of body wave attenuation in Garhwal-Kumaun Himalaya region from the datasets of 465 well located earthquakes, recorded at 52 broadband stations between 2017 and 2020. The body wave attenuation parameters <span><math><msub><mi>Q</mi><mi>P</mi></msub></math></span> and <span><math><msub><mi>Q</mi><mi>S</mi></msub></math></span> were estimated at each station by applying the extended coda normalization method for five different central frequencies ranging from 1.5 to 18 Hz. Strong frequency-dependent body wave attenuation was observed at each station over the whole region. Also, we found a significant variation of <span><math><msub><mi>Q</mi><mi>P</mi></msub></math></span> and <span><math><msub><mi>Q</mi><mi>S</mi></msub></math></span> from north to south which is consistent with geotectonic diversity beneath the study region. We have also made separate estimations of frequency-dependent relations for Garhwal and Kumaun Himalaya region in order to investigate the lateral variation in attenuation characteristics, and obtained the frequency-dependent relations as follows: <span><math><msub><mi>Q</mi><mi>P</mi></msub><mo>=</mo><mfenced><mrow><mn>30</mn><mo>±</mo><mn>3</mn></mrow></mfenced><msup><mi>f</mi><mfenced><mrow><mn>1.05</mn><mo>±</mo><mn>0.05</mn></mrow></mfenced></msup></math></span>, <span><math><msub><mi>Q</mi><mi>S</mi></msub><mo>=</mo><mfenced><mrow><mn>143</mn><mo>±</mo><mn>20</mn></mrow></mfenced><msup><mi>f</mi><mfenced><mrow><mn>0.88</mn><mo>±</mo><mn>0.07</mn></mrow></mfenced></msup></math></span> for the Garhwal Himalaya region and <span><math><msub><mi>Q</mi><mi>P</mi></msub><mo>=</mo><mfenced><mrow><mn>31</mn><mo>±</mo><mn>1</mn></mrow></mfenced><msup><mi>f</mi><mfenced><mrow><mn>1.09</mn><mo>±</mo><mn>0.02</mn></mrow></mfenced></msup></math></span>, <span><math><msub><mi>Q</mi><mi>S</mi></msub><mo>=</mo><mfenced><mrow><mn>121</mn><mo>±</mo><mn>11</mn></mrow></mfenced><msup><mi>f</mi><mfenced><mrow><mn>1.00</mn><mo>±</mo><mn>0.04</mn></mrow></mfenced></msup></math></span> for the Kuamun Himalaya region. Obtained <span><math><mi>Q</mi></math></span> values indicate strong body wave attenuation for both the region with no significant lateral variation. It may suggest the presence of crustal level folding, faulting, aqueous fluids, and metamorphic fluids below both the regions. Also, the ratios of <span><math><msub><mi>Q</mi><mi>S</mi></msub></math></span>/<span><math><msub><mi>Q</mi><mi>P</mi></msub></math></span> are high (<span><math><mo>&gt;</mo><mn>1</mn></math></span>) for the entire analyzed frequency range, suggesting a significant level of heterogeneity and tectonic complexities in the crust of the study region.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"352 ","pages":"Article 107211"},"PeriodicalIF":2.3,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141051381","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":"Midcrustal moderate-size earthquake occurrence in paleovolcanic structures off Jeju Island, South Korea","authors":"Junhyung Lee,&nbsp;Tae-Kyung Hong,&nbsp;Seongjun Park,&nbsp;Byeongwoo Kim","doi":"10.1016/j.pepi.2024.107210","DOIUrl":"10.1016/j.pepi.2024.107210","url":null,"abstract":"<div><p>A series of midcrustal moderate-size earthquakes occurred in the Korean Peninsula recently. A midcrustal <span><math><msub><mi>M</mi><mi>L</mi></msub><mn>4.9</mn></math></span> strike-slip earthquake with a fault-plane strike in N-S occurred on December 14, 2021 at the southwestern offshore region of Jeju Island, South Korea. The fault plane orientation and slip sense (faulting mechanism) hardly conform with the regional stress field. The deep focal depth and N-S directional strike-slip motion require transient changes in the medium properties and stress field. Strong ground motions of the midcrustal earthquake induce preferential dynamic stress changes in NE-SW direction, triggering subsequent aftershocks in NE-SW-directional adjacent faults. Both the static and dynamic stress changes caused by the mainshock contribute to the aftershock sequence. The number and focal depths of aftershocks decrease with distance from the mainshock. The different fault-plane orientations between the mainshock and aftershocks suggest earthquake nucleations in independent fault structures. The mainshock occurred in aseismic midcrustal paleovolcanic structure on the outskirt of a high seismicity region. The <span><math><msub><mi>M</mi><mi>L</mi></msub><mn>4.9</mn></math></span> earthquake suggests possible nucleation of earthquake in seismically-inactive paleotectonic structures, successively incurring aftershocks conforming to the ambient stress. The mainshock and aftershocks suggest that paleotectonic structures may behave as source structures to spawn earthquakes.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"352 ","pages":"Article 107210"},"PeriodicalIF":2.3,"publicationDate":"2024-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141055566","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":"A supervised machine learning approach for estimating plate interface locking: Application to Central Chile","authors":"Sebastián Barra ,&nbsp;Marcos Moreno ,&nbsp;Francisco Ortega-Culaciati ,&nbsp;Roberto Benavente ,&nbsp;Rodolfo Araya ,&nbsp;Jonathan Bedford ,&nbsp;Ignacia Calisto","doi":"10.1016/j.pepi.2024.107207","DOIUrl":"10.1016/j.pepi.2024.107207","url":null,"abstract":"<div><p>Estimating locking degree at faults is important for determining the spatial distribution of slip deficit at seismic gaps. Inverse methods of varying complexity are commonly used to estimate fault locking. Here we present an innovative approach to infer the degree of locking from surface GNSS velocities by means of supervised learning (SL) algorithms. We implemented six different SL regression methods and apply them in the Central Chile subduction. These methods were first trained on synthetic distributions of locking and then used to infer the locking from GNSS observations. We tested the performance of each algorithm and compared our results with a least squares inversion method. Our best results were obtained using the Ridge regression, which gives a root mean square error (RMSE) of 1.94 mm/yr compared to GNSS observations. The ML-based locking degree distribution is consistent with results from the EPIC Tikhonov regularized least squares inversion and previously published locking maps. Our study demonstrates the effectiveness of machine learning methods in estimating fault locking and slip, and provides flexible options for incorporating prior information to avoid slip instabilities based on the characteristics of the training set. Exploring uncertainties in the physical model during training could improve the robustness of locking estimates in future research efforts.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"352 ","pages":"Article 107207"},"PeriodicalIF":2.3,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141046448","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}