Pingtong Town is located on the fractured zone of the Wenchuan 8.0 earthquake,and is seriously damaged by the earthquake.Our observation line is centered at an earthquake exploration trench across the fractured zone in the NW-SE direction,and is about 400 m long.The results reveal trapped waves in the ruptured fault zone of the earthquake,and indicate a great difference in physical property between the media inside and outside the fault zone.The predominant frequency of the fault-zone trapped waves is about 3-4 Hz.The wave amplitudes are larger near the exploration trench.The width of the fault zone in the crust at this location is estimated to be 200 m.In some records,the waveforms and the arrival times of S waves are quite different between the two sides of the trench.The place of change coincides with the boundary of uplift at the surface. Pingtong Town is located on the fractured zone of the Wenchuan 8.0 earthquake, and is of seriously damaged by the earthquake. Our observation line is centered at an earthquake exploration trench across the fractured zone in the NW-SE direction, and is about 400 m long. The results reveal trapped waves in the ruptured fault zone of the earthquake, and indicate a great difference in physical property between the media inside and outside the fault zone. Predominant frequency of the fault-zone trapped waves is about 3-4 Hz.The wave amplitudes are larger near the exploration trench. width of the fault zone in the crust at this location is estimated to be 200 m. some records, the waveforms and the arrival times of s waves are quite different between the two sides of the trench. the place of change coincides with the boundary of uplift at the surface.