摘要
OBS2019-2测线位于南沙地块礼乐西海槽附近,向北依次穿过礼乐滩、礼乐西海槽和南海海盆,测线全长300 km.该区域处于西南次海盆与东部次海盆过渡的关键区域.通过对OBS2019-2测线的数据进行分析处理和计算模拟,得到最终的速度结构模型,模型显示洋壳区地壳厚度4~7 km,陆壳区地壳厚度9~19 km,洋陆转换带(Continent-Ocean Transition,COT)在模型120~170 km范围内,约50 km宽,地壳厚度6~9 km.同时模型揭示了一个低速带可能为中南—礼乐断裂,属于岩石圈级大断裂,推测其向南经过了礼乐西海槽.相较于东沙地块,OBS2019-2测线速度模型与穿过中沙地块的海底地震仪(Ocean Bottom Seismometer,OBS)测线速度模型具有相似的速度结构特征,因此推测礼乐地块与中沙地块相邻,共轭的可能性更大,两者在南海扩张前同属于华南大陆.
OBS2019-2 with a total length of 300 km,passing through Liyue Bank,Liyuexi Trough and South China Sea(SCS)Basin in the north,is located near Liyuexi Trough in the Nansha Block,which is a critical region in the transition between the Southwest Subbasin(SWSB)and the East Subbasin(ESB).The final velocity structure model,obtained by analyzing and modeling the OBS2019-2 data,suggests a crust thickness of 4~7 km in the oceanic crust and 9~19 km in the continental crust.With a crustal thickness of 6~9 km,the Continent-Ocean Transition(COT)zone is about 50 km wide within the model range of 120~170 km.And the model reveals a low-velocity zone that could be the Zhongnan-Liyue Fault,which belongs to the lithospheric fault and is assumed to pass southward through the Liyuexi Trough.Compared to the velocity structure of Dongsha Block,the velocity model of OBS2019-2 shows similar velocity structure features to the Ocean Bottom Seismometer(OBS)velocity model traversing the Zhongsha Block.We infer that the Liyue Block and Zhongsha Block are adjacent to each other and conjugation is more likely.Both were part of the South China Continent before the opening of the South China Sea.
作者
郭建
丘学林
黄海波
GUO Jian;QIU XueLin;HUANG HaiBo(South China Sea Institute of Oceanology,Chinese Academy of Sciences,Key Laboratory of Ocean and Marginal Sea Geology,Guangzhou 510301,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2024年第9期3386-3401,共16页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(42174110,42176081,41849908)资助.
关键词
礼乐西海槽
地壳结构
海底地震仪
洋陆转换带
中南-礼乐断裂
Liyuexi Trough
Crustal structure
Ocean Bottom Seismometer(OBS)
Continent-Ocean Transition(COT)
Zhongnan-Liyue Fault
