Correlated Features of Horizontal Movement-Deformation on the North and East Margins of the Qinghai-Xizang Block before the Kunlun Earthquake with Ms=8.1

INTRODUCTIONThe Qinghai_Xizang(Tibet)blockis praised as a“piston”in the earth dynamics systemof theChinese mainland,andis regarded asthe hotspot in geoscience study all along.The occurrence of theMS8·1strong earthquake on November14,2001,inside the Qin…

Correlated Features of Horizontal Movement-Deformation on the North and East Margins of the Qinghai-Xizang Block before the Kunlun Earthquake with Ms=8.1

The high-precision GPS data observed from the northeast margin of the Qinghai-Xizang (Tibet) block and the Sichuan-Yunnan GPS monitoring areas in 1991 (1993), 1999 and 2001 revealed that: before the Kunlun earthquake with M-S=8.1 on November 14, 2001, the dynamic variation features of horizontal movement-deformation field in the north and east marginal tectonic areas of the Qinghai-Xizang (Tibet) block had some correlated features. That is to say, under the general background of inherited movement, the movement intensities in the two areas weakened synchronously and the state of deformation changed when the great earthquake was impending. Analysis and study in connection with geological structures showed that before the Kunlun M- S 8.1 earthquake, the correlated variations of movement-deformation on the boundaries of Qinghai-Xizang (Tibet) block were related to the disturbing stress field caused by the extensive and rapid stress-strain accumulation in the late stage of large earthquake preparation. Owing to the occurrence of large earthquake inside the block, the release of large amount of strain energy, and the adjustment of tectonic stress field, in relevant structural positions (especially zones not penetrated by historical strong earthquake ruptures) in boundary zones where larger amount of strain energy was accumulated, stress-strain may be further accumulated or else released through rupture.