地震地质 ›› 1981, Vol. 3 ›› Issue (2): 9-21.

• 科研简报 • 上一篇    下一篇

喜马拉雅地区的地震活动与近期地壳运动

叶洪, 张文郁, 于之水, 夏勤   

  1. 国家地震局地质研究所
  • 收稿日期:1980-08-01 出版日期:1981-06-03 发布日期:2009-11-25

THE SEISMICITY AND THE RECENT CRUSTAL MOVEMENT IN THE HIMALAYA REGION

Ye Hong(Yeh Hung), Zhang Wenyu, Yu Zhishui, Xiu Qin   

  1. Institute of Geology, National Bureau of Seismology
  • Received:1980-08-01 Online:1981-06-03 Published:2009-11-25

摘要: 由于穿越条件的限制,用地面地质方法研究喜马拉雅地区的近期地壳运动有许多困难,但是地震活动与地震波特点可以为我们提供这方面的信息。我们对1897年以来80年间喜马拉雅地区的地震,做了以下三方面工作:1.根据地震活动与震源机制资料研究断层的现代活动方式。2.用零矢量方法确定地块运动位移矢量的方向。3.根据地震矩估算地壳滑动速率。最后,根据这三方面的工作成果,对这一地区的近期地壳运动模式做了初步讨论。

Abstract: In this paper three aspects of analysis are made for the recent crustal movement in the Himalayas on the basis of earthquake data recorded from 1897-1976.1. The characteristics of the present active faults in this region were studied by the fault plane solutions.2. The vectors of the tectonic movement in the lithosphere blocks were calculated by the null vector method.3. The rate of the crustal slip, was estimated from the seismic moment data.In light of the analysis mentioned above, a model of recent crustal movement in the Himalayas is tentatively presented as follows.1. According to the results calculated by the null vector method, the direction of the tectonic movement of the lower lithosphere in the Himalayas is NNE, and its plunge is nearly horizontal, indicating that convergence of the NNE-ward drifting Indian plate and the Eurasian plate was mainly a sort of collision in nature with intensive horizontal compression and shortening rather than underthrusting.2. The regional trend of the western part of the Himalayan arc is nearly perpendicular to the direction of the tectonic movement of the Indian plate. During the process of intensive horizontal shortening of the lithosphere. its upper part upthrusts with a rather low angle over the Ganges Plain, and now the type of movement is still going on chiefly along the main boundary fault and the Ganges Plain boundary fault. The strike of the eastern part of the Himalayas is nearly parallel to the direction of the tectonic movement of the Indian plate. Along this fault belt the Indian plate is moving NNE-ward and has a left-lateral strike slip relative to the Eurasian plate with some upthrust component.3. As a result of the intensive push of the Indian plate applied to the Himalayas, shortening of the latter at a rate of about 3.4 cm/y. was estimated. In the eastern part of the Himalayas the strain energy seems to be released chiefly by earthquake dislocations, but in the western part mainly through aseismic creeps. In the Qinghai-Xizang Plateau north of River Yarlungzangbo, the rate of shortening is probably less than that of the Himalayas. The north-south shortening of this Plateau causes the thickening of the crust and the eastward flow of the crustal materials, and consequently the intensive right-lateral strike slip along the Miju and Red River faults on the south side of this plateau.