Geometry and 3D seismic characterisation of post-rift normal faults in the Pearl River Mouth Basin,northern South China Sea  

作　　者：Yuanhang Liu Jinwei Gao Wanli Chen Jiliang Wang Umair Khan 

机构地区：[1]Laboratory of Marine Geophysics and Georesources,Institute of Deep-sea Science and Engineering,Chinese Academy of Sciences,Sanya 572000,China [2]University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Acta Oceanologica Sinica》2024年第4期25-39,共15页海洋学报（英文版）

基　　金：The National Natural Science Foundation of China under contract No.42276066;the Key Research and Development Program(International Science and Technology Cooperation Development Program)of Hainan Province under contract No.GHYF2022009;the Youth Innovation Promotion Association of CAS under contract No.2018401.

摘　　要：Based on high-resolution 3D seismic data acquired in the Pearl(Zhujiang)River Mouth Basin of the northern South China Sea,this study investigated the geometry,spatial extension,and throw distribution of the post-rift normal fault through detailed seismic interpretation and fault modeling.A total of 289 post-rift normal faults were identified in the study area and can be classified into four types:(1)isolated normal faults above the carbonate platform;(2)isolated normal faults cutting through the carbonate platform;(3)conjugate normal faults,and(4)connecting normal faults.Throw distribution analysis on the fault planes show that the vertical throw profiles of most normal fault exhibit flat-topped profiles.Isolated normal faults above the carbonate platform exhibit roughly concentric ellipses with maximum throw zones in the central section whereas the normal faults cutting through the carbonate platform miss the lowermost section due to the chaotic seismic reflections in the interior of the carbonate platform.The vertical throws of conjugate normal faults anomalously decrease toward their intersection region on the fault plane whereas the connecting normal faults present two maximum throw zones in the central section of the fault plane.According to the symmetric elliptical distribution model of fault throw,an estimation was made indicating that normal faults cutting through the carbonate platform extended downward between-1308 s and-1780 s(two-way travel time)in depth and may not penetrate the entire Liuhua carbonate platform.Moreover,it is observed that the distribution of karst caves on the top of the carbonate platform disaccord with those of hydrocarbon reservoirs and the post-rift normal faults cutting through the carbonate platform in the study area.We propose that these karst caves formed most probably by corrosive fluids derived from magmatic activities during the Dongsha event,rather than pore waters or hydrocarbons.

关 键 词：Post-rift normal faults fault throw Karst caves Corrosive fluids Pearl River Mouth Basin South China Sea 

分 类 号：P618.13[天文地球—矿床学] P631.46[天文地球—地质学]