Why 1G Was Recorded at TCU129 Site During the 1999 1Chi-Chi, Taiwan, Earthquake

Abstract

The strong-motion station TCU129 recorded a peak horizontal acceleration higher than 1 g during the 1999 Chi-Chi, Taiwan, earthquake. Yet no structural damages occurred in its vicinity. Even some old buildings not far away from the station were not damaged. There did not seem to be very strong ground motion in this area during the Chi-Chi earthquake. To resolve these conflicting phenomena, we performed microtremor surveys in this area and installed additional two strong-motion accelerographs inside station TCU129 to compare the ground-motion records between the original and new accelerographs. We also compared the ground accelerations between station TCU129 and a nearby station TCU076. The results indicate that the high peak acceleration recorded at TCU129 during the 1999 Chi-Chi, Taiwan, earthquake was due to the effects of the concrete recording pier at station TCU129, and not due to the source, path, or site effects of the earthquake. Therefore, the peak acceleration values recorded at station TCU129 should not be used in studies of peak acceleration attenuation. However, the records are still useful, especially the integrated velocity and displacement time histories, for other studies.