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Abstract The thrust-dextral slip motion of Longmenshan tectonic belt resulted in Wenchuan Ms8.0 earthquake occurred on May 12，2008. 133 groups of three-component acceleration records were collected by digital strong earthquake networks in Sichuan Province. By using these original records and some strong motion records from digital strong earthquake networks in Shaanxi and Gansu provinces，the contour lines of acceleration peak values were drawn；and they show that the anomalistic ellipse-shaped contour lines of acceleration peak values along the long axis in NE direction conform to the distribution of earthquake response intensity. The attenuation of the acceleration records shows obvious directivity effect and hanging wall effect；i.e. the peak acceleration decayed relatively slower in NE direction of the rupture propagation than in SW direction. The attenuation of peak acceleration also decayed slower on the fault hanging wall in NW direction than that in SE direction；the systemic relative higher phenomenon of the peak acceleration attenuation was more remarkable in Yingxiu—Beichuan section of the causative fault；and it can be relative to fracture pattern and progress of seismic source. Another phenomenon is that the ratio of vertical peak ground value to horizontal one near the causative fault is obviously higher than that in the seismic far-field；and the ratio is about 1.0 near the faults，which is great different with the 2/3 from Code for seismic design of buildings(GB50011–2001). Furthermore，with fault distance increasing，the peak acceleration gradually shifted to the long-period in the acceleration response spectrum，which is more obvious beyond a distance of 200 km to the causative faults；but in the near-fault distance of 100 km，there is a large velocity pulse.
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Received: 08 January 2010
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2010, Vol. 29 
