Relationship between Peak Ground Acceleration, Peak Ground Velocity, and Intensity in Taiwan

Based on the strong-motion data set from the 1999 Chi-Chi, Taiwan, earthquake and a shaking damage statistics database, we investigated the correlations between strong ground motions and earthquake damage (fatalities and building collapses) through a regression analysis. As a result, the current earthquake intensity scale It is placed on a more reliable instrumental basis. This is necessary for the real-time seismic monitoring operation in Taiwan where programs for earthquake rapid reporting (RRS) and earthquake early warning (EWS) are actively pursued. It is found that the earthquake damage statistics give a much closer correlation with the peak ground velocity (PGV) than with the peak ground acceleration (PGA). The empirical relationship between PGV and the intensity It determined in this study can be expressed as It = 2.14 × log10(PGV) + 1.89. This PGV-based intensity is particularly useful in real-time applications for damage prediction and assessment, as the damage impact of high PGV is much more important for mid-rise and high-rise buildings that are characteristic of a modern society. For smaller earthquakes (M <5), the PGVintensity correlation also out-performs the PGA-intensity correlation, as large sharp PGA spikes are often observed for rather small nondamaging events at close-in distances. However, as the lower level intensity is conventionally defined through human feelings, for even smaller events (M <3) humans are more sensitive to PGA than to PGV. Since the RRS and EWS operations are mainly dealing with large and damaging earthquakes, the above PGV-based empirical relationship should prove to be more appropriate in these real-time operations.