Strong motion PGA prediction for southwestern China from small earthquake records

Abstract

For regions without enough strong ground motion records, a seismology-based method is adopted to predict motion PGA (peak ground acceleration) values on rock sites with parameters from small earthquake data, recorded by regional broadband digital monitoring networks. Sichuan and Yunnan regions in southwestern China are selected for this case study. Five regional parameters of source spectrum and attenuation are acquired from a joint inversion by the micro-genetic algorithm. PGAs are predicted for earthquakes with moment magnitude (Mw) 5.0, 6.0, and 7.0 respectively and a series of distances. The result is compared with limited regional strong motion data in the corresponding interval Mw ± 0.5. Most of the results ideally pass through the data clusters, except the case of Mw7.0 in the Sichuan region, which shows an obvious slow attenuation due to a lack of observed data from larger earthquakes (Mw ≥ 7.0). For further application, the parameters are adopted in strong motion synthesis at two near-fault stations during the great Wenchuan Earthquake M8.0 in 2008.