MONITORING OF SLOPE SEISMIC RESPONSE DURING AFTERSHOCKS OF WENCHUAN EARTHQUAKE IN QINGCHUAN COUNTY

From May 13 to 27, 2009,the seismic responses of a slope during four aftershocks of the 2008 Wenchuan Earthquake were monitored with the 941B ultralowfrequency vibrometer and G01 generalpurpose instrument. The slope located at Wei Ganliang in Qingchuang county. The microseismic monitoring shows that relative to the 805 m elevation at the Wei Ganliang Mountain,the measured peak accelerations of ground motion at the 875 m elevation in the horizontal EW direction and vertical direction had the tendency of reduction. However,the measured peack accelerations in the horizontal NS direction had a significant multiplier effect. The magnification was up to 7 to 8 times. The main frequency of the amplitude spectrum focused on the low frequency range between 20 and 40 Hz. Analysis shows that the epicenter located on the north side of the NEE striking QingchuanPingwu fault. Along the direction of seismic wave propagation,the slope has significant an amplification effect．