Characteristics of crustal variation and extensional break-up in the Western Pacific back-arc region based on a wide-angle seismic profile  

作　　者：Jianghao Qi Xunhua Zhang Zhiqiang Wu XiangjunMeng Luning Shang Yang Li Xingwei Guo Fanghui Hou Enyuan He QiangWang 

机构地区：[1]Qingdao Institute of Marine Geology,Qingdao,China [2]Laboratory for Marine Mineral Resources,Pilot National Laboratory for Marine Science and Technology,Qingdao,China [3]Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou,China [4]School of Resource Engineering,Longyan University,Longyan,China

出　　处：《Geoscience Frontiers》2021年第3期296-313,共18页地学前缘（英文版）

基　　金：supported by the National Key Basic Research Program of China(Grant No.2013CB429701);the National Natural Science Foundation of China(Grant Nos.41606083,91958210,41606050 and 41210005);AoShan Technological Innovation Projects of National Laboratory for Marine Science and Technology(Qingdao)(2015ASKJ03);National Marine Geological Special Project(DD20190236,DD20190365,DD20190377)。

摘　　要：The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 545-kmlong active-source ocean bottom seismometer(OBS)wide-angle reflection/refraction profile in the East China Sea.The P wave velocity model shows that the Moho depth rises significantly,from approximately 30 km in the East China Sea shelf to approximately 16 km in the axis of the Okinawa Trough.The lower crustal high-velocity zone(HVZ)in the southern Okinawa Trough,with V_(p) of 6.8-7.3 km/s,is a remarkable manifestation of the mantle material upwelling and accretion to the lower crust.This confirms that the lower crustal high-velocity mantle accretion is developed in the southern Okinawa Trough.During the process of back-arc extension,the crustal structure of the southern Okinawa Trough is completely invaded and penetrated by the upper mantle material in the axis region.In some areas of the southern central graben,the crust may has broken up and entered the initial stage of seafloor spreading.The discontinuous HVZs in the lower crust in the back-arc region also indicate the migration of spreading centers in the back-arc region since the Cenozoic.The asthenosphere material upwelling in the continent-ocean transition zone is constantly driving the lithosphere eastward for episodic extension,and is causing evident tectonic migration in the Western Pacific back-arc region.

关 键 词：Western Pacific back-arc region Back-arc extension Wide-angle reflection/refraction seismic profile High-velocity zone Plate subduction retreat Tectonic migration 

分 类 号：P542[天文地球—构造地质学]