Statistical characteristics of strong aftershocks of Wenchuan earthquake and ground motion attenuation relationship
HAN Jianping;XU Jinyu;Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province, Lanzhou University of Technology;Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education Lanzhou University of Technology;
After the 2008 devastating Wenchuan Earthquake on May 12 th, a considerable number of aftershock ground motion records were obtained by both the fixed and mobile stations, which provide abundant research data for seismic risk analysis and ground motion attenuation relationship investigation. In this paper, the frequency-magnitude distribution of the aftershocks of the Wenchuan Earthquake was established through the Gutenberg-Richter relation. With the B?th law, the estimated maximum aftershock magnitude was predicted, which is close to the real value. The relationship between the aftershock occurrence rate and the time after the mainshock was fitted based on the modified Omori law. The statistical characteristics show that the distribution of the epicentral distances and the magnitudes of the aftershock records for the magnitudes ranging from 4.0 to 6.4 is relatively even, which can be used for establishing the ground motion attenuation relationships. The statistical regression analyses of the EW, NS, and UD ground motion components were carried out respectively for both the soil and bedrock surfaces, and the quantitative peak ground acceleration(PGA) attenuation relationships for the 3 components were obtained.