Relationships between strong ground motion peak values and seismic loss during 1999 Chi-Chi, Taiwan Earthquake

Abstract

A better real-time assessment of earthquake effects (i.e. seismic intensity estimation) is crucial for hazard mitigation. Especially during the aftermath of a disastrous event, significant reduction of loss can usually be realized through timely execution of emergency response measures. These effects include strong-ground shaking, ground failure, and their impact on man-made structures. The descriptive Modified Mercalli intensity scale, though still in common use in many poorly instrumented areas of the world, is out of date in areas of extensive strong-motion instrumentation. It is desirable to place the earthquake intensity scale on a more quantitative basis based on the actual recorded ground-motion shaking and carefully compiled damage records. In this paper, we investigated the relationships between earthquake loss, intensity and strong motion peak values, mainly based on the Chi-Chi earthquake. Both the strong-motion peak values and the earthquake loss are related. From the results, we found that peak ground acceleration (PGA) and peak acceleration response spectra at 1 s period (1 s Sa) values are two parameters that give slightly higher correlation coefficients than other parameters for earthquake loss analysis. For intensity estimations, the peak ground velocity (PGV) values and 1 s Sa values are better parameters in the high range and PGA is not stable for smaller earthquakes. Although PGV values give a slightly lower correlation coefficient and larger standard deviation in seismic loss analysis during the Chi-Chi earthquake, it nevertheless gives more reliable instrumental intensity over a broad magnitude range. 1 s Sa is a good parameter for both seismic losses and intensity evaluation. We thus conclude that PGV and 1 s Sa are relatively more stable in damage assessment and, at least in the high end, in intensity estimation. We shall incorporate these findings in our real-time earthquake rapid reporting and early warning systems. © 2004 Kluwer Academic Publishers.