阿尔泰山活动断裂

文中介绍了位于亚洲腹地阿尔泰山地区的活动断裂。中国阿尔泰山 (阿尔泰山西南麓 )和蒙古阿尔泰山 (阿尔泰山的东麓 )以NNW向大型走滑断裂为主 ,科布多断裂是阿尔泰山东麓的一条主要NNW向走滑断裂 ,长度近 70 0km。第四纪中晚期右旋走滑速率可达 6 10mm/a ,其上发现有长逾2 0 0km的古地震形变带。富蕴断裂则是阿尔泰山西南麓的一条主要NNW向断裂 ,中晚第四纪的走滑运动速率为 (4± 2 )mm/a ,在中国阿尔泰山的西端还发育规模相对较小的NNW向右旋走滑断裂 ,中晚第四纪走滑速率为 (2± 1)mm/a。中国阿尔泰山 (阿尔泰山的西南麓 )还发育NWW向右旋走滑逆断裂 ,其规模相对较小 ,至中国阿尔泰山西端NWW向的额尔齐斯断裂具有明显的右旋走滑性质。蒙古阿尔泰山的南端则发育近东西向的左旋走滑逆断裂。在与戈壁阿尔泰山交汇部位 ,左旋走滑运动具主导作用。戈壁阿尔泰山发育的戈壁阿尔泰断裂带断续延伸可达 10 0 0km以上 ,目前的研究认为 ,其滑动速率为 12mm/a。其中的博格德断裂上 195 7年发生了戈壁阿尔泰 8.3级地震 ,形变带长约 2 5 0km。阿尔泰山活动断裂的规模、运动强度和强地震活动表明这里不仅受到遥远的印度板块北向推挤作用的影响 ,而且受到较近的地球动力学过程的影响或控制。

THE ACTIVE FAULTS IN ALTAI MOUNTAINS

The major active faults of Altai Mountains in backland of Asian continent are introduced in this paper. The major active faults in Altai Mountains are NNW trending right-lateral strike-slip fault. Hovd fault is the largest NNW trending strike slipping fault in the eastern piedmont of Altai Mountains, with the length of 700 km and right-lateral slipping rate of 6~10 mm/a, along which a Paleoearthquake rupture zone over 200 km long was found. Fuyun fault is the major strike-slipping fault in the southwestern piedmont of Altai Mountains. Its slipping rate in Mid-Late Quaternary is (4±2) mm/a. There are also some small-scale NNW trending right-lateral strike-slipping faults in the western segment of Chinese Altai Mountains. Their total slipping rate is (2±1) mm/a. In addition, there exist some relatively small NWW trending faults in the southwestern piedmont of Altai Mountains; one of them is the Erqisi fault. Its western segment at the western end of Chinese Altai Mountains has clear right lateral strike slipping nature. While, at the south end of Mongolia Altai Mountains the W-E trending faults have left lateral strike-slipping nature. At the junction between the Mongolia Altai and Gobi Altai, the predominant movement of the E-W trending faults is left lateral strike slipping. The Gobi Altai fault zone is over 1 000 km long along the Gobi Altai Mountains. The preliminary study shows that the left lateral strike-slipping rate of the fault is around 1~2 mm/a. Bogd fault is the largest fault in the Gobi Altai fault zone. An earthquake with M=8.3 occurred in 1957 along the Bogd fault, and left a 250 km long surface rupture zone in south Mongolia. The large scale, intensive movement and strong earthquake activity of the faults in Altai Mountains indicated that this region has not only been affected by the northward intruding of India plate but also has been controlled by a local geodynamic process in Mongolia.