Trapped waves in the Qingchuan fault zone were observed at Muyu near the northeastern end of the fractured zone of the Wenchuan Ms8. 0 earthquake. The results indicate a fault-zone width of about 200 m and a great difference in physical property of the crust on different sides of the fault. The inferred location of crustal changes is consistent with land-form boundary on the surface
This article gives a description of our first study on ground rotational motion and its pre-liminary results. The ground rotational motions around vertical axis were obtained using near-field translational records of a temporal seismic array with observational distances of 1.8 to 2.7 km. The sources used are explosions with explosive of 500 kg for each. Ground rotational velocities were calcu-lated using the space derivatives of the horizontal components of translational velocities from the array. The peak ground rotational velocities （PGRV） are approximately 30 to 57 ？rad/s. Our results are very close to those from Wassermann et al. （2009）, who used both a seismic array and a rotational sensor to record an explosion in Germany and obtained PGRV values of about 50 ？rad/s. Their explosives are 150 kg, only one third of ours, but their observational distance is 250 m, much less than ours.
