琼东南盆地第四纪块体搬运体系的地震特征

SEISMIC CHARACTERISTICS OF QUATERNARY MASS TRANSPORT DEPOSITS IN QIONGDONGNAN BASIN

第四纪以来,琼东南盆地的陆坡区域广泛发育深水块体搬运体系。深水块体搬运体系是广泛发生在外陆架/上陆坡的一种沉积物搬运机制,包括滑动、滑塌和碎屑流等重力流作用过程。利用深水3D地震资料,提取振幅和相干数据,通过地震剖面、构造图和时间切片分析,揭示块体搬运体系具有丘状外形、波状反射结构、弱振幅和连续性差的地震特征,内部整体比较杂乱,主体发育褶皱,趾部发育逆冲断层,具有塑性流体特征。结合南海构造背景分析,认为研究区第四纪沉积速率高并位于地震多发带,构成了块体搬运体系的形成条件和触发机制。

Mass transport deposits （MTDs）are widely distributed in Quaternary sedimentary sequences of the continental slope in the Qiongdongnan basin, South China Sea. MTDs are a sediment transport mechanism often occurring in the outer shelf/upper-slope area. MTDs include slide, slump and debris flow. Based on the high resolution deepwater three-dimension seismic data, seismic amplitude and coherence data are obtained. Through the seismic profile, structural map and time slice of target strata, profile characteristics and internal structure of MTDs are revealed. MTDs are characteristic of seismic reflection of mound, hummocky, chaotic, low amplitude and poor continuity. Folds and thrust faults which are attributed to plastic deformation structures occur in MTDs, and folds occur in the main part, thrust faults in the toe part. The high sedimentation rate of Quaternary sequence and the location in the earthquake belt are the trigger mechanism of MTDs in the study area.