我国近海地震活动特征及其与地球物理场的关系

对我国近海海域有历史记载以来的地震的震级、震中参数进行了整理分析,并分析了各海域地震活动的时、空分布规律,根据历史地震资料,确定海域受历史地震影响的最大影响烈度,然后初步分析了地震活动与现代构造应力场、地球物理场的关系.研究发现:(1)近海海域历史地震资料的精度较低,中强地震存在明显的遗漏.(2)渤海、台湾海峡、南海北部地震活动性较强,黄海次之,东海最弱.(3)近海海域的震害主要来自海域地震和近岸陆地强震的影响,影响强弱依次为:渤海、黄海、东南沿海、东海.(4)现代构造应力场以水平向构造应力场作用下的走滑运动为主,最大主应力方向受印度板决和太平洋板块、菲律宾海板块的俯冲挤压方向影响.(5)海域地球物理场,特别是布格重力异常、地壳厚度分布与强震构造带的空间分布关系的相关性较好.本文的研究结果可为我国海域及滨海重要工程的抗震设防、海域地震危险性区划提供一定的基础.

The seismicity of China offshore seas and its relationship with geophysical fields

The parameters of historical earthquakes occurred in China offshore areas, such as magnitude and epicenter, are collected from different references, and the spatio-temporal characteristics of these intense earthquakes in different seas are analyzed. The maximal influence intensity in different areas is determined on the basis of historical earthquake records. And a preliminary analysis is carried out about the relations of seismic activity and modern tectonic stress field and geophysical fields. The study shows that: (1) The precision of historical earthquake parameters is rather low, and there exists obvious missing of moderate earthquakes.(2) The seismic intensity of the Bohai Sea, Taiwan Strait and north of South China Sea are relatively strong, Yellow Sea is much weaker, and East China Sea is the weakest. (3) The earthquake influences are from the offshore earthquakes and strong earthquakes occurred on the land near the seas, the order of influence intensity is: Bohai Sea, Yellow Sea, Southeast China seas and East China Sea. (4) The tectonic stress field is strike-slip motion, and the direction of maximal stress is controlled by the subduction of the Indian plate, Pacific plate and Philippine Sea plate. (5) There is good correlation of the geophysical fields with strong earthquake distribution, especially the Bouguer gravity anomaly and the thickness of crust. The results can provide some knowledge for the seismic fortification of important engineering in seas and on the near-shores, and the seismic hazard zonation of China seas.