中蒙地块的水平运动及应变特征

CHARACTERISTICS OF HORIZONTAL MOVEMENT AND STRAIN OF SINO-MONGOLIA BLOCK

GPS观测结果显示中蒙块体的位移速率较小,块体各部分的位移方向存在差别,说明块体有差异活动但不显著.连续应变场的应变率参量值在10-8/a以下;主压应力轴方向为NE74.6°,与该区内的浅源强震震源机制解的P轴方向基本一致.由应变产生的贝加尔湖裂谷的裂开速率为4.71 mm/a,最大主应变率为34.34×10-9 /a,张应变主轴方向NW310.49°,垂直于裂谷走向;嫩江断裂带和萝北-营口断裂带为走滑兼挤压或拉张活动断裂,位移速率和应变率都较小,活动性不显著.2003年8月16日巴林左旗5.9级地震和2004年3月24日东乌珠沁旗6.4级地震均发生在由1999～2003年GPS资料得出的多种应变速率参量的相对高值带和应变率高梯度带上.

The results from the GPS measurement show that the displacement rate of Sino-Mongolia block is small and the displacement directions of the parts of the block are different. It means that the activity is not obvious. The strain parameter values of the continuous strain field are under 10^-8/a. The direction of principal compressive strain axis of the block is NE74.6°, it is basically consistent with the direction of P axis of the focal mechanism solution of the shallow strong earthquake in this area. The split rate of the Baikal lake rift caused by the strain is 4.71 mm/a, the maximum principal strain rate is 34.34 × 10^-9/a, the direction of principal axis of tensile strain is NW310.49°, it is orthogonal to the strike of the rift. The Nenjiang fault zone and Luobei-Yingkou fault zone are the strike-slip faults with the compressive or extension activity, and the displacement and the strain rate are small, it means that their activities are not obvious. The Balinzuoqi earthquake of Ms5.9, August 16, 2003, and Dongwuzhuqinqi earthquake of Ms6.4, March 24, 2004, occurred in the zone of high rate value and high strain gradient zone from the GPS data in 1999-2003.