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????????????2004~2007???GPS??????????????溯??????????????????????????????????????????????μ????????????????????????????????????????????????????????????????ε????????????????????嶫????????????????????????????????б??κ????????????????????????????2008??????????????????????????θ?????????????????????????????????????ж??????????????????????????????????????-????????????????????????-?????????????????ο??????????????????????????????????????????θ?????????????????????????й??

Characteristics of Strain at Eastern Margins of the Tibetan Plateau from GPS Data

The displacement model of surface horizontal motion is calculated by using a multi-surface function based on the GPS data from the eastern Tibetan plateau from 2004 to 2007, and the strain field on the spherical coordinates is given. Through comparison of earthquakes that occurred in the observation periods and the fault distribution in the area, the relationship among horizontal motion, strain space distribution, strong earthquakes and regional tectonic deformation is discussed. The results indicated that EW trending crustal shortening is remarkable in Songpan block and the deformation in Sichuan-Yunnan block is dominated by left-lateral shear and rotation. Furthermore, before the Wenchuan earthquake, the Longmenshan fault displayed a secondary high value of strain energy, the surface strain showed a pressure property, with the strain increasing rapidly, and the middle segment of the Longmenshan fault has been locked. The crustal zone in the western segment of the Xianshuihe fault shows NE-SE shortening and in the eastern segment the crustal displays NW-SE shortening. Sichuan-Yunan diamond block is an area with high value of strain energy and surface strain gradient, the western region of Jinshajiang is dominated by strong strain energy, which is associated with the tectonic stress of Qiangtang block.