8.1级震后青藏块体东北部水平形变态势与地震有序活动研究

STUDY ON HORIZONTAL DEFORMATION AND ORDERLY SEISMIC ACTIVITIES IN THE NORTHEASTERN QINGHAI-XIZANG BLOCK AFTER 8.1 EARTHQUAKE

青藏块体东北部2003年最新GPS复测揭示:昆仑山口西8 1级地震后本区水平运动变形较前变异显著,以甘青块体西部出现的与NE向挤压背景相反的张性运动变形为主要标志,且区域总体应变幅度增大。结合地震有序活动分析认为:本区目前的水平运动变形态势,与8 1级大震及随后青藏块体中西部发育的NE向中强以上地震条带在较短时间内释放了大量的压应变,使得青藏块体北部区域NE向推挤的应力场失衡(西侧的区域应力场强度衰减、东侧的应力场增强)密切相关;因而青藏块体北部大区域应力场趋于平衡过程将有利于块体东北边缘应力应变加速积累和破裂错动。

The latest GPS observation result in 2003 of the northeastern Qinghai-Xizang block reflects that:after Ms 8.1 earthquake,this area shows more remarkable horizontal movement deformation than before.As main sign,the west of Gansu-Qinghai block appears tensional movement being contrary to NE compressional background.Moreover,there is an increase in the total regional strain field.By combining with analysis of orderly seismic activities,we got the conclusion that:the present deformation status of horizontal movement closely relates to a vast amount of compression strain released in a short time by 8.1 earthquake and aftershock developed NE seismic zone of more than medium magnitude in the middle-western Qinghai-Xizang block,it makes NE compressional strain field in the northern Qinghai-Xizang block lost balance(the intensity of west-side stress field decreases,but the east-side stress field increases).Therefore,the balance process of large-range stress field of the northern Qinghai-Xizang block will help the northeast margins of block to accelerate strain and stress accumulation and rupture dislocation.