Coseismic slip distribution of the 2008 Wenchuan great earthquake constrained using GPS coseismic displacement field

The May 12, 2008 Wenchuan earthquake ruptured the Yingxiu-Beichuan and Guanxian-Jiangyou faults, and produced surface ruptures of similar to 240 km and similar to 70 km in length along the two faults, respectively. In this study, the coseismic displacement field derived from GPS observations collected before and after the quake is used to invert for the fault geometry and slip distribution of the rupture. The result shows that the Yingxiu-Beichuan fault dips to the northwest at a moderate angle of similar to 41 degrees at the southwest end, and the fault plane gets progressively steeper northeastward along strike, reaching a dip angle of similar to 73 degrees at Qingchuan. The averaged width of fault plane is 10 similar to 18 km. Slip caused by the earthquake is characterized mainly by thrust motion with a modest right-lateral strike slip component at the south segment of the fault. As the rupture travelled farther northeastward, the thrust component tapers down gradually, and the dextral component becomes dominant at the northeast end of the rupture. The slip distribution on the Yingxiu-Beichuan fault shows two high-slip concentrations of up to 7.8 m and 7.4 m, respectively. The two high-slip concentrations are just near the Yingxiu town and Beichuan city,which suffered the greatest fatalities and structure damages during the quake. The seismic moment release is estimated to be 6.70 X 10(20) N . m, corresponding to an M(w)7.9 earthquake.