收稿日期:2012-03-05
基金项目:行业科研专项GNSS地壳形变场相关信息的提取及在地震趋势预测中的应用(201208006)资助.
基金项目:行业科研专项GNSS地壳形变场相关信息的提取及在地震趋势预测中的应用(201208006)资助.
备注
利用1999～2007年和2009～2011年青藏高原东北缘地区水平形变观测与处理结果,分析了汶川、玉树地震前后该区域水平形变场及其变化,得出:(1)1999～2007年水平运动的大小与方向变化明显,但清晰有序,相对运动一般在15 mm/a以内,2009～2011年的水平运动轮廓虽然与1999～2007年相似,但变化可辨,主要体现在震源较近的地域;(2)1999～2007年的主压应变优势方向为南东—北西向,有序与一致性较强,值域一般在(±35～38)×10-9/a之内,最大主应变区呈带状分布于祁连构造带上,2009～2011年最大主应变的大小及空间分布则有一定的差别,震中附近最大约为180×10-9/a,但主应变方向与1999～2007年基本保持一致;(3)1999～2007年最大剪切应变率大小的空间分布呈北西向条带状,较大值域的条带为祁连构造带达27×10-9/a,2009～2011年最大剪切应变率的空间状态不同于以前,最大值位于震源及其附近地区接近120×10-9/a,其他区域相对较小;(4)1999～2007年的旋剪形变呈北西向条带左、右旋交替的分布状态; 2009～2011年则没有如此清晰,最大值也位于震中及附近地域。总之,震后区域形变场有较大的调整,可能还在继续中。
Based on the GNSS observation data and its processing result from 1999 to 2007 and from 2009 to 2011 in the northeastern edge of Qinghai-Tibetan plateau,we analyzed the horizontal deformation field and its variation before and after Wenchuan M8.0 and Yushu M7.1 earthquakes.The results show as follows:(1)The rate and direction of horizontal movement changed obviously,but it was clear and ordered,its relatively movement was within 15mm/a from 1999 to 2007.Although the movement profile from 2009 to 2011 was similar as before,there was little difference especially in the region near by the epicenters.(2)The principal compressive strain from 1999 to 2007 had more orderliness and consistency.Its value is between ±35×10-9/a and its superior direction is SE-NW.The region of maximal principal compressive strain showed zonal distribution and located in Qilian tectonic zone.The size and space distribution of maximal principal compressive strain from 2009 to 2011 is different,the maximal value of principal compressive strain near by the epicenter is about 180×10-9/a.However,the direction of it remained the same.(3)The space distribution of the maximal shear strain rate from 2009 to 2011 showed a banding distribution along the north-west direction,the more value of bending which lay in Qilian tectonic belt was 27×10-9/a.The spatial shape of the maximal shear strain rate from 2009 to 2011 is different from the result of 1999～2007,the maximum value of the strain rate from 2009 to 2011 which lay in the epicenter and its adjacent region was 120×10-9 /a.The strain rate in the other region is less.(4)The revolving shear deformation from 1999 to 2007 showed bending distribution along North-West direction and was orderly alternate change with left-lateral and dextral.However,the state of revolving shear deformation from 2009 to 2011 was not clear,and there was the maximum value was around epicenter and its adjacent area.In a word,there were major changes of crustal deformation after earthquakes and it might be on still.
