用爆破地震研究湖南省深部构造与地震的关系

STUDYING THE RELATIONSHIPS BETWEEN THE DEEP STRUCTURE AND EARTHQUAKE IN HUNAN PROVINCE BY EXPLOSION EARTHQUAKE

利用湖南省棋梓桥万罗山定向爆破观测资料,使用迭代法对棋梓桥至酃县剖面进行了二维构造反演,得到4层地壳结构模型:界面1埋深1.8—4km,v<6.0km/s;界面2埋深10.5—15km,6.0km/s<v<6.4km/s;界面3埋深21—22.2km,6.4km/s<v<6.8km/s;界面4埋深33—37km,6.8km/s<v<7.8km/s。其中界面2为C界面,界面4为M界面。二者变化梯度小。界面3在衡阳地块消失。由于M界面平稳,未受深层物质侵蚀以及C界面虽在衡阳地块边缘出现挠曲,但其埋藏较浅,围压低,因此认为该区难以积累足以发动强烈地震所需的应变能。

By using the observation data of directional blasting at Wanluo Mountain of Qiziqiao, Hunan Province, the inversion of two-dimen-sional structure from Qiziqiao to Lingxiao is done by the iteration method and the model of crustal structure in four layers are gained showing in the following: the interface of No. 1 is buried deep in 1.8-4 km, V<6.0 km/s; of No.2 in 10.5-15 km, 6.0 km/s, <V<6.4km, of No. 3 in 21-22.2 km, 6.4 km/s<V<6.8 km/S; and of No, 4 in 33-37 km, 6.8 km/s<V<7.8 km/s. Among them, the interface of No. 2 names C interface, and the interface of No.4 names M interface, the gradient of them are in small change. The interface of No. 3 is dispeared in the block of Hengyang. AS M interface is in stable, so it is not eroded by deep materials, while C interface is crooked at the block edge of Hengyang, but it is not buried in deepth and its confining pressure is in low state. Therefore we think that it is difficult to accumulate enough strain energy that need to start a strong motion earthquake.