1997年玛尼79级地震的构造环境和地表破裂带特征

1997年11月8日西藏玛尼79级地震发生在羌塘盆地北缘.本文利用LANDSAT影像，研究地震的地质构造背景，研究表明玛尼79级地震发生在NEE向玛尔盖茶卡—若拉错断裂带上，这是一条全新世明显活动的地壳深断裂.利用CBERS_1影像，研究地震地表破裂带的几何特征，100000分之一CBERS_1影像上由地震裂缝、地震陡坎和断塞塘组合显示的线性影像清楚地反映出地震地表主破裂带的形迹，可有效地进行破裂带的分段和长度量测.结果表明玛尼79级地震形成的地震地表主破裂带西起羌塘盆地北缘，绥加山南麓的白雪湖湖积平原上，向东延伸到双端湖西岸，长110km，走向N70 80°E.可分为白雪湖—玛尔盖茶卡、玛尔盖茶卡—朝阳湖、朝阳湖—双端湖３段.多时相MSS、TM影像分析表明，1997年玛尼79级地震是先存地震地表破裂带再次破裂的结果.

The tectonic condition and the feature of surface rupture zone of the Mani earthquake (Ms 7.9) in 1997

On November 8, 1997, an Ms=79 earthquake occurred in Mani of Xizang autonomous region at the northern edge of Qiangtang Basin. Qiangtang is an uninhabited region in northern Tibet where the climate is cold, the air is thin, and the field investigation condition is very arduous. LANDSAT images are used to study the geological and tectonic background of the earthquake. The result shows that the earthquake occurred in the NEE striking Margai Caka Rola Co rupture zone, which is an active deep fault since the Holocene. CBERS 1 images of 1/100000 scale are used to study the geometric characteristics of surface rupture. The Mani surface rupture zone is showed as a linear feature composed of cracks, uplifts, and dammed pools, which can be used to measure the length and mark off sections of the rupture. The result shows that the major surface rupture zone of the earthquake appears at the northern edge of Qiangtang Basin, in the Baixue Lake plain at the southern foot of Suijia Mountain, and extends eastward to the western bank of Shuangduan Lake. It is 110km long and trending N70 80°E. The surface rupture zone can be divided into 3 sections: Baixue Lake Margai Caka section, Margai Caka Chaoyang Lake section, and Chaoyang Lake Shuangduan Lake section. The analysis of multi phase MSS and TM shows that the surface rupture is re fracturing along an old fault.