Tectonophysics最新文献

{"title":"Lithospheric flexure and effective elastic thickness under the Ulleung Basin in the East Sea using gravitational coherence","authors":"Masume Akbari ,&nbsp;Hojjat Kabirzadeh ,&nbsp;Chang Hwan Kim ,&nbsp;Chan Hong Park ,&nbsp;Youn Soo Lee ,&nbsp;Jeong Woo Kim","doi":"10.1016/j.tecto.2024.230609","DOIUrl":"10.1016/j.tecto.2024.230609","url":null,"abstract":"<div><div>To estimate a non-uniform effective elastic thickness (<span><math><msub><mi>T</mi><mi>e</mi></msub></math></span>) of lithosphere across Korean Peninsula and the Surrounding Seas (KPSS), we employ gravitational coherence analysis between gravity anomalies and topography/bathymetry data in the Fourier domain. Exploring crustal flexure and effective elastic thickness variations can offer insights into flexural strength, and evolutionary mechanics of the lithosphere under Ulleung Basin (UB). Our approach involves two scenarios: a large study area spanning the KPSS, and a more targeted investigation focused on UB. Dividing the study area into overlapping windows enables us to recover non-uniform <span><math><msub><mi>T</mi><mi>e</mi></msub></math></span> values over the targeted regions. The UB study area is divide to 200 km by 200 km windows, and KPSS is divided to 400 km, 600 km, and 800 km windows to recover both short wavelengths and long wavelengths of <span><math><msub><mi>T</mi><mi>e</mi></msub></math></span>. Our results reveal a <span><math><msub><mi>T</mi><mi>e</mi></msub></math></span> range of 843 km for KPSS and recovered <span><math><msub><mi>T</mi><mi>e</mi></msub></math></span> range from 1 to 10 km for UB. The estimated elastic thickness values in southern part of this basin are smaller compared to central and northern parts. These findings are consistent with prior estimations and comparative studies within the region, improving the understanding of UB's lithospheric properties. The recovered <span><math><msub><mi>T</mi><mi>e</mi></msub></math></span> values for UB (<span><math><msub><mi>T</mi><mi>e</mi></msub><mo>&lt;</mo><mn>6</mn><mspace></mspace><mi>km</mi></math></span>) suggests a young and weak oceanic lithosphere under this region. The alignment between recovered <span><math><msub><mi>T</mi><mi>e</mi></msub></math></span> configuration and tectonic features in KPSS displays a large-scale lithospheric structure.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"896 ","pages":"Article 230609"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142889087","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":"1-D velocity model from local earthquake localization and receiver functions for the southern Neuquén basin: Insights into lithosphere structure and dynamics","authors":"Sebastian Correa-Otto ,&nbsp;Silvana Spagnotto ,&nbsp;Guido M. Gianni ,&nbsp;Mario Giménez","doi":"10.1016/j.tecto.2024.230602","DOIUrl":"10.1016/j.tecto.2024.230602","url":null,"abstract":"<div><div>Knowledge of the lithospheric structure is key to understanding the seismotectonic characteristics of convergent margins. In this study, we provide a robust one-dimensional velocity model for the Añelo region, located within the Neuquén extensional basin in Argentina, with the aim of illuminating the lithospheric characteristics of the back-arc region of the southern central Andes. Data from a temporary network of broadband stations operational from October 2014 to March 2020 was utilized. We employed two distinct seismological techniques for obtaining models with varying resolutions at multiple scales and depths. On the one hand, upper thin layers were obtained by the inversion of a model based on hypocenters from local earthquakes, and on the other, we calculated receiver functions to estimate thicker and deeper layers. By combining both methods we were able to obtain a joint and accurate velocity model, a crucial tool for conducting seismicity studies in the region and achieving precise determinations of earthquake locations. Moreover, the analysis of velocity variations offers valuable insights into the complex lithospheric structure beneath the study area, shedding light on the poorly understood seismotectonic activity in the Andean retroarc. We suggest that the presence of a weakened or hot lithospheric mantle beneath the southern Neuquén Basin may be linked to the Payenia mantle anomaly. This anomaly likely softens the upper plate, concentrating deformation and intraplate seismicity, as documented in the vicinity of the study area.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"896 ","pages":"Article 230602"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100109","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":"Factors affecting the Pacific plate subduction towards and under the Changbaishan volcanic province since the Cenozoic: Insights from geodynamic modeling based on data assimilation","authors":"Tao Zhu ,&nbsp;Diandian Peng ,&nbsp;Lijun Liu","doi":"10.1016/j.tecto.2024.230607","DOIUrl":"10.1016/j.tecto.2024.230607","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The origin of the Changbaishan volcanic province (CVP) has been considered to correlate with the subduction of the Pacific plate, so it is necessary to dynamically reconstruct the subduction history of the Pacific plate towards and beneath the CVP since the Cenozoic for probing the mechanism of the CVP. Many parameters affect slab subduction dynamics, so how to choose these parameters reasonably is the urgent issue to be solved during the reconstruction. A lot of analogue and numerical models have been used to study the effects of these parameters, but almost all of them have not considered a slab subduction history. In addition, seismic tomographic models have manifested that there is a high-speed anomaly zone extending over 1300 km within the mantle transition zone (MTZ) beneath the CVP. The zone is belived to consist of the Pacific slab in its eastern part and a segment of delaminated continental lithosphere (DCL) in its western part, bounded by approximately 120°E. A reasonable geodynamic model should reproduce both the Pacific slab and the DCL. Accordingly, in order to provide a reference for selecting geodynamic model parameters, we initially develop a series of three-dimensional (3D) thermochemical geodynamic models with data assimilation, in which several parameters are varied independently. These parameters encompass the Clapeyron slopes (&lt;em&gt;γ&lt;/em&gt;&lt;sub&gt;410&lt;/sub&gt; and &lt;em&gt;γ&lt;/em&gt;&lt;sub&gt;660&lt;/sub&gt;) and thicknesses (δ&lt;em&gt;h&lt;/em&gt;&lt;sub&gt;410&lt;/sub&gt; and δ&lt;em&gt;h&lt;/em&gt;&lt;sub&gt;660&lt;/sub&gt;) of the 410-km and 660-km discontinuities, the viscosities in the lower mantle (&lt;em&gt;η&lt;/em&gt;&lt;sub&gt;&lt;em&gt;lw&lt;/em&gt;&lt;/sub&gt;), the mantle transition zone (&lt;em&gt;η&lt;/em&gt;&lt;sub&gt;&lt;em&gt;mtz&lt;/em&gt;&lt;/sub&gt;) and the middle part of the lower mantle (&lt;em&gt;η&lt;/em&gt;&lt;sub&gt;&lt;em&gt;mlw&lt;/em&gt;&lt;/sub&gt;), seafloor age (&lt;em&gt;t&lt;/em&gt;&lt;sub&gt;&lt;em&gt;o&lt;/em&gt;&lt;/sub&gt;), the densities of the oceanic crust (representing it with the buoyancy ratio &lt;em&gt;B&lt;/em&gt;&lt;sub&gt;6&lt;/sub&gt;) and asthenosphere (Δ&lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;&lt;em&gt;asth&lt;/em&gt;&lt;/sub&gt;), as well as the density jump across the 660-km discontinuity (Δ&lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;660&lt;/sub&gt;). Subsequently, we primarily investigate how these parameters influence the westward movement distance, sinking depth, and structure of the Pacific slab, as well as whether geodynamic models incorporating these parameters can predict the high-speed anomaly zone. Finally, for reasonably reproducing the Pacific slab and the DCL beneath the CVP, we propose a suggested range of these parameters: &lt;em&gt;γ&lt;/em&gt;&lt;sub&gt;660&lt;/sub&gt; may lie within the range of −2.0 to −3 MPa/K; &lt;em&gt;η&lt;/em&gt;&lt;sub&gt;&lt;em&gt;lw&lt;/em&gt;&lt;/sub&gt; and &lt;em&gt;η&lt;/em&gt;&lt;sub&gt;&lt;em&gt;mlw&lt;/em&gt;&lt;/sub&gt; may range from 30 to 50 and should not exceed 75; &lt;em&gt;B&lt;/em&gt;&lt;sub&gt;6&lt;/sub&gt; may be set to −0.48, which corresponds to a mean density of 3.0 g/cm&lt;sup&gt;3&lt;/sup&gt; for the Earth's oceanic crust; the lower limit of the &lt;em&gt;t&lt;/em&gt;&lt;sub&gt;&lt;em&gt;o&lt;/em&gt;&lt;/sub&gt; may be adopted; &lt;em&gt;η&lt;/em&gt;&lt;sub&gt;&lt;em&gt;mtz&lt;/em&gt;&lt;/sub&gt; may be 1.0 to 2.5; Δ&lt;em&gt;ρ&lt;/em&gt;&lt;sub&gt;&lt;em&gt;asth&lt;/em&gt;&lt;/sub&gt; should adopt a reasonable and more negative value; and Δ&lt;em&gt;ρ&lt;/","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"896 ","pages":"Article 230607"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143179318","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":"Rupture directivity and seismogenic structures of strong aftershocks in the northeastern rupture zone of the 2008 Wenchuan earthquake","authors":"Ting Liu ,&nbsp;Xiaohui He ,&nbsp;Yipeng Zhang ,&nbsp;Zhiliang Liu ,&nbsp;Wenjun Zheng ,&nbsp;Peizhen Zhang ,&nbsp;Yi Wang","doi":"10.1016/j.tecto.2024.230605","DOIUrl":"10.1016/j.tecto.2024.230605","url":null,"abstract":"<div><div>Three strong aftershocks (M_S6+) occurred in the northeastern rupture zone of the 2008 M_W7.9 Wenchuan earthquake within three months. No surface ruptures were observed, and the seismogenic faults remain unclear. Resolving the source parameters and seismogenic structures of these strong aftershocks is essential for clarifying the rupture termination mechanism of the mainshock and for future seismic hazard assessment. In this study, we determined the point source parameters of eight moderate to strong aftershocks and the rupture directivity of three strong aftershocks through regional and teleseismic waveform modeling. The focal mechanisms of these aftershocks are diverse, including both strike-slip and thrust-slip types, with centroid depths ranging from the middle crust (12–19 km) to the shallow part (3–5 km), highlighting the complexity in the rupture termination zone. The rupture directivity analysis shows that the strike-slip May 25 event (Mw6.0) ruptured from SW to NE along the right-lateral plane (60°/81°/173°) for ∼7 km, the strike-slip July 24 event (Mw5.5) on ruptured from NNE to SSW along the right-lateral plane (16°/67°/147°) for ∼6 km, and the thrust-slip August 5 event (Mw5.9) ruptured upwards along the northeast dipping plane (339°/56°/83°) for 6–8 km. The strike of ruptured faults changes from NE to NNE, differing from the Qingchuan fault. The estimated stress drop of the event in the middle crust (∼19 km, 9.3 MPa) is larger than that of the shallower event (∼4 km, 1.9 MPa), possibly due to the low strength of the shallow crust. Moreover, the rupture direction of the July 24 event is opposite to that of the mainshock, potentially due to the Bikou block's differing bi-material contrast, which may have hindered the northeastward extension of the mainshock's rupture.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"896 ","pages":"Article 230605"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867446","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":"Mesoscale fractures control the scale dependences of seismic velocity and fluid flow in subduction zones","authors":"Yuya Akamatsu ,&nbsp;Hanaya Okuda ,&nbsp;Manami Kitamura ,&nbsp;Michiyo Sawai","doi":"10.1016/j.tecto.2024.230606","DOIUrl":"10.1016/j.tecto.2024.230606","url":null,"abstract":"<div><div>Natural geological systems contain porosity structures of various scales that play different roles in geophysical properties, fluid flow, and geodynamics. To understand seismic activity associated with high pore-fluid pressure and fluid migration in subduction zones, it is necessary to explore the scale dependence of geophysical properties such as seismic velocity and permeability. Here, we compare laboratory-measured ultrasonic velocity measured on core samples from the Susaki area in the Shimanto accretionary complex, SW Japan, with sonic velocity measured by borehole logging experiments. Results show that P-wave velocity decreases from the laboratory (∼6 km/s) to the borehole scales (∼5 km/s). This scale-variant effect can be explained by a differential effective medium model whereby mesoscale porosity that is undetectable at the ultrasonic wavelength is introduced into the matrix phase with microscale porosity. Assuming typical apertures for micro- and mesoscale fractures, we estimate that the effective permeability can increase to 10⁻¹²–10⁻¹¹ m² with increasing in the mesoscale porosity and decreasing P-wave velocity down to 4–5 km/s. These results indicate that seismic velocity anomalies and related seismic activity are associated with the presence of mesoscale fractures in subduction zones.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"896 ","pages":"Article 230606"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867474","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":"Unraveling the dynamics of seismicity in the Baihetan Reservoir Area with AI-based catalog","authors":"Longfei Duan ,&nbsp;Cuiping Zhao ,&nbsp;Lianqing Zhou ,&nbsp;Ce Zhao ,&nbsp;Wei Guo ,&nbsp;Mengqiao Duan ,&nbsp;Kezhen Zuo ,&nbsp;Lisheng Xu","doi":"10.1016/j.tecto.2024.230601","DOIUrl":"10.1016/j.tecto.2024.230601","url":null,"abstract":"<div><div>In this study, we used LOC-FLOW to process continuous waveforms recorded by 55 stations near the Baihetan Reservoir in China, which is the second-largest reservoir in the world with installed capacity, from January 2021 to July 2022. We identified 53,838 seismic events with relative location errors within tens of meters, representing a fourfold increase compared to the manual catalog, and recalling approximately 99.0 % of the events listed therein. Our location results indicate that the seismicity after the impoundment of the Baihetan Reservoir is mainly controlled by the regional geological structure, mostly distributed on the sub-structures or fractures near the main fault. Moreover, there are significant differences in seismicity on both sides of the Jinsha River, which is attributed to the different lithology. In some areas, the seismicity gradually migrates away from the reservoir inundation zone. Some clusters exhibit significantly different migration speeds, which may be related to the mechanisms or underground structure. In addition, some events migrate along the depth which is attributed to the earthquake causing rock fractures to allow groundwater infiltration. Below the area submerged by the reservoir water, there are not only notable differences in the <em>b</em>-values, but also distinct correlations between water depths and earthquake rates at those different depths. This may be due to the influence of both water load and pore pressure on rocks in shallow areas, facilitating rapid stress release through microearthquakes. Conversely, in the deeper, stress accumulation results in larger-magnitude earthquakes with weak pore pressure increasing. Our results show that high-resolution earthquake catalogs can reveal the dynamic response of earthquakes to reservoirs and help understand the factors that control their distribution and magnitude. This is of great significance for future earthquake tracking in reservoir areas and for the study of other reservoirs around the world.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"896 ","pages":"Article 230601"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143179319","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":"Geophysically-BASED structural framework and tectonic evolution of the Brazilian equatorial margin","authors":"Francisco Gabriel Ferreira de Lima ,&nbsp;Walter Eugênio de Medeiros ,&nbsp;Emanuel Ferraz Jardim de Sá","doi":"10.1016/j.tecto.2024.230604","DOIUrl":"10.1016/j.tecto.2024.230604","url":null,"abstract":"<div><div>The Brazilian Equatorial Margin (BEM) encompasses a WNW to NW-trending segment along which a complex set of sedimentary basins were developed from the Neobarremian to the Albian. Recent discoveries of hydrocarbon reserves in the continental margins of Ghana, in Africa, and Guyanas/Suriname, in South America, have heightened interest in studying the Equatorial Atlantic margins. In this context, it is crucial to understand better the mechanisms that led to the formation of these basins, whose exploratory potential is still open. Most studies on the BEM either focus on small areas without comparing results to their African counterparts or involve regional reconstructions that overlook hyperextended crustal sections, thus hindering a more accurate fit. This work aims to define the deep crustal architecture of the BEM and delineate the transition from continental to strictly oceanic crust based on the merging of gravimetric, magnetic, and multichannel 2D seismic data from various sources, types, and resolutions. Our findings have allowed us to categorize the BEM into four domains, according to classification schemes and models proposed by Manatschal (2004), Osmundsen and Péron-Pinvidic (2018), Péron-Pinvidic et al. (2013, 2015): proximal (PD), necking zone (NZ), distal domain (DD), and oceanic domain (OD). These domains feature a predominance of Aptian to Albian NW-SE normal and oblique-slip faults, as well as N<em>E</em>-SW folds and thrusts, all of which are associated with E-W strike-slip or oblique-slip faults. The nature of the distal domain zone can vary from gradual to abrupt, depending on its location and the dominant structural style in each margin segment. The oceanward limit of the DD is marked by a continent-ocean boundary (COB) that runs orthogonal to the present-day oceanic fracture zones, unlike what has been reported in other studies. Our defined boundaries ensured a good fit between the continental crusts of the BEM and the African Equatorial Margin (AEM) during the Cenomanian period.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"896 ","pages":"Article 230604"},"PeriodicalIF":2.7,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143104708","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":"Timing of the switchover from thrusting to normal faulting in the Cretan nappe pile, Greece","authors":"Uwe Ring ,&nbsp;Charalampos Fassoulas ,&nbsp;I. Tonguç Uysal ,&nbsp;Johannes Glodny ,&nbsp;Kui Tong ,&nbsp;Andrew Todd","doi":"10.1016/j.tecto.2025.230652","DOIUrl":"10.1016/j.tecto.2025.230652","url":null,"abstract":"<div><div>Contractional faults and shear zones are often reactivated by normal faulting and the timing of this kinematic switchover is critical for better understanding orogeny, especially the formation and exhumation of high-pressure rocks. We report two fault gouge ages of ∼30 and ∼25 Ma from the contact zone between the high-pressure Phyllite-Quartzite Unit and the overlying, weakly metamorphosed Tripolitza Nappe in central Crete, southern Aegean Sea, Greece. This contact, the Damasta shear zone, is commonly regarded as a segment of the Cretan Detachment, the age of which is not well known. The dated gouge dominantly shows early top-to-the-S kinematic indicators, with some indication of a top-to-the-N reactivation. Illite/muscovite grain-size fractions of 0.5–0.2 μm and 0.2–0.1 μm yielded, within error, similar K<img>Ar ages of ∼30 Ma. These internally consistent ages can be interpreted as the timing of a first faulting event, which we interpret to be associated with the dominant set of top-to-the-S kinematic indicators. Three K<img>Ar ages of ∼25 Ma were obtained from two separate &lt;0.1 μm and a single &lt;0.2 μm grain-size fraction. This robust age of the finest grain-size fractions reflects the final faulting increment, considered to date top-to-the N normal shearing. Because the ∼25 Ma age overlaps with high-pressure metamorphism and subsequent rapid exhumation of the Phyllite-Quartzite Unit, we regard the age to be related to the Cretan Detachment in central Crete. Published data show that the upper parts of the Phyllite-Quartzite Unit started to be underthrust to the north between 36 and 29 Ma. Therefore, we relate the fault gouge ages of ∼30 Ma to this underthrusting event. We conclude that the switchover from contractional to normal faulting on the Cretan Detachment occurred at about 25 Ma.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"899 ","pages":"Article 230652"},"PeriodicalIF":2.7,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143204527","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 geoelectric structure of the Indian plate at the western extremity of the Bundelkhand craton and Sharda Depression in the Ganga Basin","authors":"A. Manglik,&nbsp;M. Suresh,&nbsp;N.N. Chakravarthi,&nbsp;G. Pavankumar","doi":"10.1016/j.tecto.2025.230653","DOIUrl":"10.1016/j.tecto.2025.230653","url":null,"abstract":"<div><div>The latest episode in the geodynamic evolution of the Ganga Basin invokes continent-continent collision, Himalayan mountain building, and flexure of the Indian plate, which resulted in deposition of thick alluvial sediments in the basin masking the geological heterogeneities of the Indian plate. In recent years, a series of magnetotelluric (MT) studies in the central Ganga Basin have brought out information about its basement and crustal structure. In the present study, we have covered the region between Gwalior and Tanakpur falling at the western extremity of the Bundelkhand craton (BKC) in south and the super-deep Sharda Depression in north (at the Himalayan foothills) by a 330 km long profile to delineate the crustal structure of the region. The geoelectric model of the crustal structure derived from 2-D inversion of broadband MT data reveals the presence of the BKC underneath the alluvial sediments as a resistive northward dipping block in this region also, implying that the BKC extends northward of its presently known boundary shown in the geological map of the region. This cratonic block is buried beneath about 5 km thick moderately resistive rocks of the Vindhyan Supergroup. The results also reveal the presence of an upper-thick Proterozoic rift basin with its deepest part more than 30 km thick within the Sharda Depression, and two lithospheric mantle conductors in the central sector of the profile indicating the possibility of the presence of a significant conductive anomaly at deep lithospheric level. The top conducting layer in the model consisting of the Shiwaliks and Recent alluvium deposited in the flexural environment gradually thickens northward and attains a thickness of about 5 km at the foothills. The results reveal that the crustal structure of this part of the Ganga Basin is highly heterogeneous across the basin.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"899 ","pages":"Article 230653"},"PeriodicalIF":2.7,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349238","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":"Moho depth variations of Zealandia from gravity data inversion and implications for continental breakup","authors":"Xuliang Feng ,&nbsp;Xiangyu Zong ,&nbsp;Xiaodong Wang ,&nbsp;Liu Yang ,&nbsp;Jiayue Ma","doi":"10.1016/j.tecto.2025.230643","DOIUrl":"10.1016/j.tecto.2025.230643","url":null,"abstract":"<div><div>The thickness of the Earth's crust, along with the relief and characteristics of the Moho discontinuity, serves as a critical constraint for numerous geoscientific investigations. By removing the gravitational effects of topography, seawater, sediment, and thermo-gravitational effects from the lithosphere in Zealandia and its adjacent regions, we isolate the gravity anomaly associated with the Moho discontinuity to compute its depth. We determined the intercept of the linear relationship between Moho depth derived from the global crust model CRUST1.0 and corresponding Moho gravity anomalies as an estimate for mean Moho depth. A laterally variable crust-mantle density contrast was initially obtained using Bouguer plate formula based on both CRUST1.0-derived Moho depths and observed gravity anomalies; this was subsequently rescaled utilizing the slope of linear regression between actual Moho gravity anomalies and fitted gravity anomalies computed from CRUST1.0-derived Moho depths alongside our initial density contrast estimates. The results calculated via Parker-Oldenburg formula indicate that Zealandia's Moho depth primarily ranges from 8 to 28 km, while crustal thickness varies between 4 and 26 km. These values are significantly greater than those typical of oceanic crust but remain less than those characteristic of continental crust. Within our study area, identified ocean basins show a decreasing trend in crustal thickness relative to both oceanic crust age and increasing water depth. When considering only areas where crustal thickness is less than 16 km on scatter plots, Middleton Basin and Lord Howe Basin display substantially greater thicknesses compared to New Caledonia Basin and Fairway Basin. This observation suggests that if these four basins possess oceanic crusts beneath them, then it is likely that the oceanic crust underlying Middleton and Lord Howe Basins predates that found beneath New Caledonia and Fairway Basins, implying that post-Zealandia separation from Gondwana involved rifting predominantly linked to subduction rollback of the Pacific Plate.</div></div>","PeriodicalId":22257,"journal":{"name":"Tectonophysics","volume":"898 ","pages":"Article 230643"},"PeriodicalIF":2.7,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143072476","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}