洪洞临汾大震震源断层的相互作用和地震趋势分析

Analysis on the interaction between the focal fault of Hongtong and Linfen earthquake and its earthquake tendency

山西临汾地区1303年和1695年发生了洪洞(M8)和临汾(M7 3/4)两次相距最近特大地震。地震所在区域至今仍有持续不断的小震活动。我们根据1670次中、小地震精确震源定位结果和149个小地震的震源机制。通过震源三维空间分布和震源机制解的分析,认为洪洞地震和临汾地震的强相互作用是解锁,因此导致临汾地震提前发生;此外,2者之间还存在弱相互作用,并且和随机发生的地震达到一种平衡。2次大地震对区域所积累的应变基本释放完毕,难以再形成与应力场一致的大破裂,使得临汾地区连续的地震活动以中小地震的形式体现,连续300多年都没有5级以上地震发生。估计今后临汾地区的这种低水平活动将继续下去,发展趋势是安全的。

In 1303 and 1695, two near strong earthquakes occurred at Hongtong （M8） and Linfen （M73/4 ） in Linfen area of Shanxi Province, where zmall earthquakes have been continually occurring till now. Through analysis on the distribution of 1670 medium and small earthquakes and 149 focal mechanisms, we concluded that the strong interaction between Hongtong and Linfen earthquakes is deblocking, which caused Linfen earthquake occurred early. Moreover, there was a kind of weak interaction between the two earthquakes, which got a bal- ance with the occurrence of random earthquakes. As the regional stress accumulated had been released completely after the two large earthquakes, it is unlikely to form a new large fracture that matches the stress field. Therefore, the earthquakes in the area have been mainly medium and small ones, and there have been no over 5 earthquake for 300 years. This phenomenon will continue, and the area is safe at present.