南海北部滨海断裂带珠江口段精细几何结构研究

The Littoral Fault Zone is not only an important seismic control and seismic structure in the northern continental margin of the South China Sea, but also the boundary fault between the standard continental crust of the South China and the thinned continental crust of the continental margin. It is significant for the geological hazards evaluation, and the formation and evolution research of the South China Sea. This proposal aims to study the geological structure of the Littoral Fault Zone in the Pearl River Estuary, based on 17 newly acquired multi-channel seismic profiles. We mark the characteristic horizons and get the detailed structure of each profile according to seismic reflection characteristics constrained by previous drilling data and seismic profiles. Then, the location of Littoral Fault Zone on each profile is determined according to the characteristics of horizon faults and reflection from fault plane. Combined with the characteristics on gravity anomaly maps, the location and distribution of Littoral Fault Zone are obtained. The morphological characteristics and fault displacement of corresponding strata on both sides of the Littoral Fault Zone are analyzed to reveal its long-term activity. Based on the geometric structure of the Littoral Fault Zone, the kinematics characteristics are discussed and the tectonic evolution process is determined. This study provides basic data and scientific basis for the earthquake resistance and prevention in the Guangdong-Hong Kong-Marco Greater Bay Area, and formation and evolution of the South China Sea.

滨海断裂带是南海北部陆缘重要的发震控震构造，也是华南陆区正常型陆壳和南海陆缘减薄型陆壳的边界断裂，对于地质灾害评估以及南海形成演化研究有着重要意义。本申请拟以新采集的17条多道地震剖面为切入点，以滨海断裂带珠江口段为研究对象，以已有钻井资料和地震剖面为约束，根据地震反射特征标定特征层位，从而得到各剖面的精细地层结构；按照研究剖面上层位断错和断面波反射特征，结合滨海断裂带的重力响应特征确定滨海断裂带的准确位置及平面展布。在此基础上，分析滨海断裂带两侧对应地层的形态特征及断距，揭示其长期活动规律和活动性；根据滨海断裂带的几何结构分析运动学特征，进而确定其构造演化过程，为粤港澳大湾区的防震抗震及南海的形成演化研究提供基础数据和科学依据。

滨海断裂带是南海北部地震活动强度大、频度高的地震带，也是华南陆区正常型陆壳和南海陆缘减薄型陆壳的边界断裂，对于地质灾害评估以及南海形成演化研究有着重要意义。本次研究对采集到的17条多道地震剖面进行层位标定，根据其地震反射特征对其进行追踪，划出地震剖面上断裂，得到各条地震剖面的精细地层结构；随后以高精度的地震剖面为主，在相邻测线之间参考原始重力异常、重力垂向一阶导、水平一阶导以及水平梯度模等多种重力数据，将各条剖面上滨海断裂带的位置连起来，从而获得研究区内滨海断裂带的精确位置及范围；最后根据地震剖面上面标注出来的地层及断裂信息，并结合南海北部的构造演化史，分析了滨海断裂带以及南海北部断裂的多期演化特征，认为晚中生代起，断裂活动性质发生过多期次的转换，且深、浅部断裂具有继承和再次活化的特征。