昆仑山口西M_S=8.1级地震的形变应变场研究

A STUDY ON THE STRAIN FIELD ASSOCIATED WITH THE M_S=8.1 KUNLUNSHAN EARTHQUAKE

根据昆仑山口西 8.1级地震前后GPS测点的位移速率 ,用弹性模型公式计算了地壳应变参数 .应变参量的变化表明 ,震前在地震区附近以压应变为主 ,应变速率较大 .位移速率矢量显示出震前的震中地区相对周围为活动性较弱的“稳定”地区 .地壳的形变和应变揭示出孕震体在挤压状态下积累了较高的应变势能 .8.1级地震的同时期由于地壳释放了巨大的应变能而应变速率变化显著 .计算结果表明 ,地震所产生的应变达到 4 .5× 10 -6以上 .发震断裂带的平均左旋走滑量是 3.31m(89°E～ 96°E)

Based on the velocities of GPS sites before and after the M8.1 Kunlunshan earthquake,the crustal strain parameters are calculated with the elastic model.The variation of strain parameters indicates that the seismic area and its surroundings were dominated by compressive strain with a larger velocity before the earthquake.The vectors of the velocities show that the epicentral area before the earthquake was “stable” with weaker seismicity relative to the surroundings.The crustal deformation reveals that the seismogenic body has accumulated higher stain potential energy under compression.As the M8.1 earthquake occurred,the strain velocity varies significantly due to releasing large amounts of strain energy.The calculated result indicates that the strain generated by the earthquake is up to 4.5×10 -6 and the average left-lateral strike slip on the seismogenic fault is 3.31 m (89°E～96°E).