伊犁盆地新构造运动与地震

NEOTECTONIC MOVEMENT AND EARTHQUAKES IN ILI DEPRESSION BASIN

从新生代地层展布及形变入手,说明伊犁盆地早第三纪以区域性抬升为主,晚第三纪开始断陷。当时盆地范围较大,沉积中心在我国境内;第四纪初构造变动强烈,南、北天山全面隆起,盆地渐趋缩小,其后仍以整体抬升为主,但东部抬升速率大于西部而带掀斜性质,沉积中心西移至巴尔喀什湖。中更新世冰川发育,晚更新世多风成黄土。用阶地(14)~C测年数据推算喀什河上游的抬升速率为2.86mm/a,中、下游为1.86mm/a。山体隆升与局部断陷使老断裂多次活动,新断裂相伴产生,喀什河断层垂直运行速率为2.5mm/a。断裂活动的压性特征及水文网络反映新构造应力场为南北方向的强烈挤压。本文还简述了伊犁盆地4条主要活动断裂带及其与地震活动的关系,特别指出契利克深大断裂震级频次高居北天山榜首,应加强地震地质基础性研究工作。

The movement along Ili depression basin, been regionally uplifted during Eogene period and started faulting during Neogene period, could be explained with Cenozoic strata distribution and deformation. In that time,the depression range was larger,and the depositional centre was in China. In Early Quaternary period, structural movement was strong with South & North Tianshan comprehensively uplifted. While the depression range was gradually narrow. But in a whole, it was lifted and sloped from east to west,the depositional centre was moved to Bal -Kashi Lake. In Modio -Pleistocene,glacier was developed well,more loess were formed in later period of Pleistocene. The rates of elevations in Kalshi river upper reaches was 2. 86mm/a,and in the middle &- lower reaches were 1. 86 mm/a,calculated by 14C,the uplifting in mountain range and depression in some areas induced the movement on faults and old fractures many times and produced new fractures. The vertical movement rates of Kalshi river fault were 2. 5 mm/a,the fractures and water network reflecting Neotectonical stress field were characterized by strong compression of meridional direction. Briefly,the author studied the main active fault zones in Ili depression and seismicities with them, placing the emphasis on the Qilic large deep fault,on which the seismic energy and frequency were occupying a leading place in North Tianshan. The author suggests to strengthen the foundation research work on seismic geologies along the fracture.