昆仑山与汶川强烈地震对青藏块体东北缘地壳运动及应变积累的影响

The Influence of the Kunlun Mountains and Wenchuan Strong Earthquakes on the Crustal Movement and Strain Accumulation in the Northeastern Margin of Qinghai-Xizang Block

充分应用GPS、区域水准、跨断层等地形变观测资料,借助非震负位错反演,结合地震活动,综合研究2001年11月14日昆仑山Ms8.1级地震对青藏块体东北缘地壳运动与应变积累的影响。通过分析笔者认为,青藏块体内部Ms8.1级巨大地震能量释放产生的扰动应力场对NE向主压背景应力场的调制作用,导致块体边界构造区域地壳差异运动和应力应变状态发生变化。其中,对阿尔金断裂东段与祁连山断裂带西段的应变积累状态反映减缓为主的影响,而对祁连山断裂带中东段则反映促进应变积累为主的影响。这种影响是一定时期、一定程度的。近期青藏块体东北缘区域应力场处于昆仑山、玉门、民乐等地震后的恢复状态。而由2008年5月12日汶川Ms8.0地震后有限的GPS、跨断层短水准观测资料,可推测汶川地震对甘川交界东段-甘川陕交界区应变积累状况一定程度促进影响。

Making full use of crustal deformation data obtained from GPS,regional leveling and cross-fault means,aided by the inversion of negative dislocation,and combined with seismic activities,the authors studied the influence of the Ms8.1 Kunlun Mountains Great Earthquake of November 14,2001 on the crustal movement and strain accumulation in the northeastern margin of Qinghai-Xizang block.The result shows that it was the adjustment action of disturbance stress field caused by this enormous seismic energy releasing inside Qinghai-Xizang block in the northeastward compressional background field that led to the variation of the crustal difference movement and the stress-strain state in the block boundary.To some extent and for a period of time,the action mainly found expression in the reduction of strain accumulation in the eastern segment of the Altyn Tagh fault and the western segment of the Qilian Mountain fracture zone,and in the promotion of strain accumulation in the middle-eastern segments of the Qilian Mountain fracture zone.Presently the regional stress field of the study area reflects the recovering state after the Kunlun Mountains,Yumen and Minle earthquakes.Moreover,based on limited data obtained from GPS,short-leveling and cross-fault means after the Wenchuan Earthquake of May 12,2008,the authors consider that the Wenchuan Earthquake promoted the strain accumulation in the eastern segment of the Gansu-Sichuan boundary as well as along the Gansu-Sichuan-Shaanxi boundary.