中国东南沿海地区地震的精定位研究

应用中国地震台网229个台站在2008至2017年期间记录的9826个地震事件体波走时数据,采用地震双差定位方法反演了中国东南沿海地区的地震位置。结果显示,东南沿海地区构造活动对地震活动有控制作用。在现今活动较强的块体边缘,地震活动集中呈条带状线性分布,优势方向与构造带方向一致;在现今活动性较弱的块体内部,地震分布离散或稀疏,无成带分布现象。在广东南澳岛北部出现两处线性分布的地震,长度分别约200和40 km,走向均为北偏东70°。其位置与前人根据重力资料推测的断裂位置一致,由于无已知断裂构造与其对应,此处可能是尚未发现的隐伏断裂。在南澳岛南部海域巴士断裂与滨海断裂交汇处,地震沿断裂大量聚集,剖面显示滨海断裂倾向为东南且倾角大。新丰江水库地震深度均在12 km内,较构造地震的深度浅。

Study on Precise Location of Earthquakes in Coastal Areas of Southeast China

Based on the body wave travel time data of 9826 seismic events recorded by 229 stations of China seismic network from 2008 to 2017,the seismic location in the coastal areas of Southeast China is inversed by using seismic double difference location method.The results show that tectonic activity in the southeast coastal area has a controlling effect on seismic activity.At the edge of the block with strong activity,the seismic activity is concentrated in a strip linear distribution,and the dominant direction is consistent with the direction of the tectonic belt;within the block with weak activity,the seismic distribution is discrete or sparse,and there is no zonal distribution.There are two places with linear distribution of earthquakes in the north of Nan'ao Island,Guangdong Province.The length is about 200 km and 40 km respectively,and the strike is 70°north by East.The location of the fault is consistent with the position of the fault inferred by predecessors according to the gravity data.Since there is no known fault structure corresponding to it,it may be an undiscovered hidden fault.At the intersection of Bashi fault and Binhai Fault in the southern sea area of Nan'ao Island,a large number of earthquakes gather along the fault.The profile shows that the Binhai Fault tends to the southeast and has a large dip angle.The seismic depth of Xinfengjiang reservoir is within 12 km,which is shallower than that of tectonic earthquake.