Three dimensional velocity model and its tectonic implications at China Seismic Experimental Site,eastern margin of the Tibetan Plateau

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外文摘要：The China Seismic Experimental Site(CSES)is located at the intersection of the Tibetan Plateau,South China Block,and Indian Plate and has complex geological settings and intense crustal deformation,making it one of the most seismically active areas in Chinese mainland.A high-resolution,three-dimensional(3D)crust-mantle velocity structure is crucial for understanding seismotectonic environments,lithospheric deformation mechanisms,and deep dynamic processes.We first constructed a high-vertical-resolution 3D initial velocity model using the joint inversion of receiver functions and surface waves and then obtained a 3D P-and S-wave velocity model(CSES-VM1.0)with the highest lateral resolution of 0.25° for the CSES using double-difference tomography.Owing to the limitations of the Sn observation data,the resolution of the S-wave velocity model in the lower crust and upper mantle was reduced,making it closer to the initial model provided by joint inversion.A comparison with explosive-source seismic data showed that the synthetic P-wave first-arrival travel times of the new model were closer to the observations than those of the previous velocity models.The velocity cross-sections across the source areas of the 2022 Lushan Ms6.1 and Ludian Ms6.8 earthquakes reveal that the former earthquake occurred near a weak contact zone between the Tibetan Plateau and Sichuan Basin,and the rupture of the latter earthquake occurred in a granitic area,with the northern end blocked by rigid high-velocity bodies.A clear high-velocity anomaly zone is distributed along the western margin of the Yangtze Block,revealing the spatial distribution of Neoproterozoic intermediate-basic intrusions.This high-velocity zone significantly controls the morphology of fault zones and influences the rupture processes of major earthquakes.Two northeast-southwest and north-south trending high-velocity anomalies were found near Panzhihua,potentially related to Neoproterozoic and Middle-Late Permian intermediate-basic intrusions.The imaging results revealed the spatial distribution of the Lincang granitoid batholith,the uplifted zone of the central axis fault in the Simao Basin,and the Ailaoshan complex belt in the southwestern CSES,demonstrating a higher spatial resolution compared to previous results.Our velocity model provides an essential foundation for deep structural studies,high-precision earthquake locations,and strong ground motion simulations in the CSES.

外文关键词：

Eastern Tibetan PlateauChina Seismic Experimental SiteYangtze BlockVelocity modelDouble-difference tomography

作者：

Jianping WU、Yan CAI、Wei WANG、Weilai WANG、Changzai WANG、Lihua FANG、Yaning LIU、Jing LIU

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作者单位：

Institute of Geophysics,China Earthquake Administration,Beijing 100081,China

Beijing Baijiatuan Earth Science National Observation and Research Station,Beijing 100095,China

Institute of Geophysics, China Earthquake Administration, Beijing 100081, China

Beijing Earthquake Agency,Beijing 100080,China

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基金：

International Earthquake Science Data Center at the Institute of Geophysics,China Earthquake AdministrationChina Earthquake Network Center for providing the seismic dataNational Natural Science Foundation of ChinaSpecial Funds for Basic Scientific Research Business Fees of Institute of Geophysics,China Earthquake Administration

项目编号：

2022YFF0800601U2039204DQJB21Z03

出版年：

2024

DOI：

10.1007/s11430-023-1293-4

中国科学:地球科学(英文版)

中国科学院

中国科学:地球科学(英文版)

影响因子：1.002

ISSN：1674-7313

年,卷(期)：2024.67(7)