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2008年5月12日四川汶川发生Ms8.0级地震,龙门山断裂带的映秀-北川断裂和灌县-江油断裂同时发生破裂,分别形成了240多公里和70多公里长的地表破裂带,最大垂直错距和水平错距分别达到6和4.9m.利用GPS获取的地表形变资料,揭示了大区域、远场同震位移场,发现地壳形变以映秀-北川断裂为中心,两侧发生相向运动和强烈的水平缩短;而且青藏高原东缘的向东运动幅度大于四川盆地向西的运动幅度.5.12汶川大地震还具有右旋走滑分量,GPS定量地揭示了映秀一带南段的右旋水平位移很小,北川县城以北的北段具有明显的右旋位移,但幅度仍然小于水平缩短幅度.垂直同震位移在龙门山断裂带东侧的成都平原以下降为主,断裂上盘只在距断裂很近处观测到了向上的运动,很快又转为下降运动,这种运动图像与高角度逆断裂产生的弹性位移场类似.上述观测事实对于进一步研究岩石圈构造运动、地震动力学特征及判定未来地震趋势等都具有十分重要的意义.
On May 12, 2008, a Ms 8.0 earthquake hit Wenchuan, Sichuan, where the Yingxiu-Beichuan fault and the Guanxian-Jiangyou fault of the Longmen Shan fault ruptured at the same time, forming surface ruptures of over 240 km and over 70 km respectively. The maximum vertical offset and horizontal offset are respectively 6 and 4.9m. Using the surface deformation data acquired by GPS, the co-seismic displacement field in large area and far field is revealed. It is found that the crustal deformation takes the Yingxiu-Beichuan fault as the center, The eastward movement of the eastern margin of the Qinghai-Tibet Plateau is greater than that of the westward movement of the Sichuan Basin.55 Wenchuan Earthquake also had a dextral strike-slip component, and GPS quantitatively revealed the right-lateral rotation of the southern section of Yingxiu The horizontal displacement is small, and the north section north of Beichuan County has a significant right-lateral displacement, but the amplitude is still less than the horizontal shortening. The vertical coseismic displacements are mainly located in the Chengdu Plain on the east side of the Longmenshan fault zone. The upward movement was observed very close to the fault and quickly turned back to a descending motion similar to the elastic displacement field produced by high-angle reverse fracture.The above observations are of great value to further study of rock The stone ring tectonic movement, the earthquake dynamic characteristic and decides the future earthquake tendency are all very important.