Abstract: Two earthquakes of magnitude 5.6 and 5.1 occurred at the juncture of Haicheng county and Xiuyan county, Liaoning Province, on November 29,1999 and January 12, 2000, respectively. The epicenter intensity of both earthquakes is Ⅶ degree. The long axes of isoseismic line of them are in NWW direction. The problems concerning the regional geological background and the seismic area and the seismogenic fault are analyzed based on the characteristics of tectonics, neotectonics, deep structure, focal mechanism and preferred orientation of isosismic lines. It is suggested that the two earthquakes are caused by a repeat movement of the seismogenic fault of the M_S 7.3 Haicheng earthquake of February 4.1975.

Key words: Haicheng-Xiuyan, Seismogenic fault, Geological structure

摘要： 1999年11月29日和2000年1月12日在辽宁海城-岫岩交界地区分别发生了5.6级和5.1级地震,两次地震的震中烈度均达到Ⅶ度,等震线长轴方向为NWW向。根据地质构造、新构造、深部构造、震源机制和等震线延伸方位等资料,分析了区域和震区的地质构造背景以及发震构造,认为这两次地震是由1975年海城7.3级地震的发震构造再次活动而引起的,仍与北西向活动断裂有关。

关键词: 海城-岫岩, 发震构造, 地质构造