In order to study the characteristics of ground motions at the two dam sites damaged during the great Wenchuan earthquake in 2008, the motions at two observation stations nearby are synthesized in this paper. 30 finite fault based hybrid source models of the great Wenchuan earthquake with magnitude 8.0 is built. The global and local parameters are both generated from the truncated Normal distribution with mean and standard deviation values estimated by a set of semi-experiential calibration laws and from the regional seismo-tectonics, structure of the crust, and seismicity. A representative source model is then chosen from the corresponding response spectrum mostly close to the average one. The result motions are presented, and the characteristics of the time histories, response spectra and the peak accelerations are quite close to the recordings.

The ground motions on two dam sites during the great Wenchuan earthquake with magnitude 8.0, motions are synthesized from 30 finite fault based hybrid source models and inversed regional parameters of source spectrum and motion attenuation. The results show that the peak ground acceleration values are less than those estimated directly from the Intensities Ⅹ and Ⅺ at the two sites, with mean values 259 and 716 gals. The motion at Shapai is much stronger than that at Zipingpu, and the spectrum is also wider than the latter, but the corresponding duration is shorter during the earthquake.