西北地区近期地壳水平运动与构造变形特征

Characteristics of Recent Horizontal Crustal Movement and Tectonic Deformation Features in the Northwest China Region

利用截止2004年的西北地区GPS和跨祁连-龙首山构造带的红外测距观测资料,借助最小二乘配置、弹性块体边界负位错模型及单一力源反演,研究昆仑山口西8.1级大震前后西北地区水平形变应变场的动态演化特征;尤其是大震3年后,即当前的构造形变与应力场态势;获取活动块体及其边界断裂上可能反映中强以上孕震背景的高应变能积累区、段,以及可能的潜在震源。结果表明:青藏块体北缘地区经8.1级大震后的短期松弛和调整,目前正在恢复印度板块北东向碰撞推挤背景场的主控作用。而北天山构造带中段及其与西段的交汇区、南天山构造带中西段及其与西昆仑构造带的交汇区、阿尔金断裂中段、祁连山构造带中东段及其与海原断裂的交汇区、西秦岭北缘断裂与庄浪河断裂东南延伸线的交汇区域等具有相对高应变能积累背景;临泽与海原这两个地区也反映一定程度的应变能积累状态。

Making use of observation data of GPS in the northwest China region and infrared distance-measuring crossing the Qilian-Longshoushan fault zone up to 2004, aided by the least square collocation and inversion of negative dislocation model for the boundaries of elastic blocks and the singular force-source, the dynamic evolution features of deformation and strain fields before and after the Ms = 8.1 earthquake in the west of Kunlun Mountain Pass, especially, recent tectonic deformation and stress field status three years after this earthquake have been studied; the possible regions or segments of active blocks and their boundaries reflecting accumulation background of high strain energy of producing earthquakes over middle magnitude, have been obtained, as well as the potential epicenter. The results show that： after short-term laxation and adjustment in the northern margin of Qinghai-Xizang block after the Ms = 8.1 earthquake, now the main control action of background field of northeastward pushing of the Indian plate is recovering. Moreover, the medium-segments of northern Tianshan fault zone and its meeting region with the western segment, the medium-western segments of southern Tianshan fault zone and the meeting region with Western Kunlun fault zone, medium-segment of the Aerjin fault, medium-eastern segments of the Qilianshan fault zone and its meeting region with the Haiyuan fault, the meeting region of northern margin fault of west Qinling Range and the southeastward expanding line of Zhuanglanghe fault have background of accumulation of high strain energy; Linze and Haiyuan also reflect accumulation of strain energy to some degree.