用GPS研究南天山(伽师)地区现今地壳变形

RESEARCH ON PRESENT CRUSTAL DEFORMATION IN THE SOUTHERN TIANSHAN (JIASHI), CHINA BY GPS GEODESY

伽师地区现今地壳运动方式、变动幅度和形变应变特征对研究该地区孕震环境具有重要作用 .利用 1 994和 1 998年两次 GPS大地测量 ,我们监测到伽师地区相对于北天山哈萨克地块的地壳缩短速率大约为 1 9mm/a,与 2 0世纪以来地震学 (地震矩张量 )资料估计的速率(约 1 3mm/a)相比 ,GPS测定的速率高约 50 % .大地测量与地震学对南天山 (伽师 )地区地壳运动速率的估值差异 ,既可能说明该地区 2 0世纪以来存在大量无震、震间应变 ,也可能表示至今与地震活动有关的断层变动尚不足以消减整个天山地区的现今变形 .无论何种可能 ,从应力应变积累的角度看 ,都意味着天山西段及帕米尔东北侧一带发生强震的可能性将长期存在 .

The pattern and range of present crustal movement as well as characteristic of deformation strain play a key role in cognizing seismogenic mechanism in the Jiashi, Xinjiang, northwestern China. Using GPS geodesy in 1994 and 1998, here we give geodetic evidence of rapid convergence of about 19 mm/a across the western Tianshan, which is about 50% greater than the seismic moment solution (13 mm/a) by estimateon of major earthquake in the 20th century. The discrepancy of deformation rate between geodetic observation and seismic energy releasing indicates, not only there exist a lot of aseismic and inter seismic strain in the western Tianshan, but also seismic fault slip in this century could not enough to compensate actively faulting and folding in the whole area. Whichever it maybe, from the view of accumulation of stress strain, it suggests that there will be potential strong earthquakes in the western segment of Tianshan and the northeastern corner of Pamir in a long period.