THE STRONG MOTION RECORDS OF THE Ms 8.0 WENCHUAN EARTHQUAKE BY THE DIGITAL STRONG EARTHQUAKE NETWORK IN SICHUAN AND THE NEIGHBORING REGION
The M s 8.0 Wenchuan Earthquake of May 12, 2008 resulted in oblique dextral-thrust motion in the Longmen Shan tectonic belt resulted. During this earthquake event, 133 sets of three-component acceleration records were collected by the digital earthquake network in Sichuan Province. By using these records and some strong motion records from the networks in Shanxi and Gansu provinces, contours of peak ground acceleration were determined. These contours are elliptically shaped with the major axis oriented in a northeast direction. The peak acceleration decayed more gradually toward the northeast, parallel to the rupture propagation than toward the southwest, indicating a directivity effect. The peak acceleration also decayed more gradually toward the northwest, on the hanging wall, than toward the southeast on the footwall. A relatively high rate of attenuation in the peak acceleration was also evident on the Yingxiu-Beichuan section of the fault; this can be attributed to the seismic source fracture pattern and rupture progress. The measured peak vertical and horizontal ground acceleration components were far larger than the design values prescribed by the Code for Seismic Design of Buildings (GB50011-2001). As distance from the rupture increased, the acceleration response spectrum gradually became dominated by long-period motions. A large velocity pulse was also measured at a distance of about 80–100 km from the fault.