Analysis of peak ground accelerations during the Chichi earthquake, Taiwan: application to seismic hazard evaluation

Attenuation laws are widely used in order to estimate the peak ground accel eration that may occur at a given locality during an earthquake, for hazard evaluation purposes. However, these simplified laws should be regarded acc eptable only in the first approximation, because numerous significant param eters at the local and regional scales are often ignored. We examined the r elationship between distance and peak acceleration based on examples from t he dense accelerometric network of Taiwan, specifically for the Chichi dest ructive earthquake. We thus observed significant discrepancies between the predicted and observed accelerations, resulting from (1) near-field saturat ion, (2) amplification in sedimentary basins, and (3) hanging wall effect. We mapped the residual accelerations (difference between observed and predi cted peak ground accelerations). This highlights the role of the regional s tructure, independently revealed by the geological analysis, as a significa nt factor that controls the transmission of the seismic accelerations. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS .