吉林省松原地区1119年63/4级地震的发震构造条件

Causative Tectonic Conditions of the Historic Earthquake (M=63/4) in 1119 in Songyuan Area

1119年6级地震是东北地区震级较大的地震,目前对其发震构造背景缺乏深入的研究。本文从深部构造背景、浅层构造条件和深浅部构造关系等方面,对1119年地震的发震构造背景作了剖析。研究认为,本次地震的宏观震中位于扶余-前郭一带,地质构造上,该区处于松辽盆地中央凹陷和东南隆起的交接部位;深部构造背景上,该区是莫霍面起伏的拐点,存在北东向基底断裂和北西向深部断裂,前者规模较大,晚新生代有弱活动,是新构造单元分界线,后者则规模小,且已停止活动;从地球物理场特征看,该区重力场和电场呈北东或北北东走向,背景简单,是东西两密集异常值的转换带。这些特征表明,不同新构造单元相交位置可能容易产生能量的积累而成为孕育地震的有利环境。文章最后对东北地震区几次中强地震的发震部位进行了讨论与分析,认为对于中国东部弱地震区,不同新构造单元的结合地区是中强震孕育的有利部位。

Proceeded from the deep tectonic setting and superstructure,this artical analysed the seismic structure conditions of the earthquake in 1119. It was indicated that the connection between different neotectonic units likely accumulated energy,became the favorable earthquake\|pregnant enviroment. Observing the deep structures and geophysical field circumstances of this region, it could be found that it was in the upper mantle upwelling area,also the abnormality gradient zone and the inflection\|point of Mohorovich discontinuity,the NW\|trend deep fracture and NE\|trend basal fracture intersected in this area.Seismic situation in Northeast China has been further discussed. It has suggested that we should pay more attention to the injection of different neotectonic units in the research of moderately strong earthquakes in East China.