Rapid Determination Of Epicentral Distance Using P Waveforms Recorded At Single Station

Recent rapid industrialization and economical growth of Korea have seen a rapid increase in population and social overhead capitals such as construction for nuclear plants, dams, roads, etc. The early warning system can enhance the safety of these newly constructed facilities from possible seismic hazards. In this study, we assess the method proposed in a previous study to estimate the epicentral distance using the first arrival of P wave recorded at a single station and quantify the accuracy of estimates at many stations across the peninsula. The quick estimation of epicentral distance is important for an early warning system because it can be used for quick determination of earthquake magnitude. In order to quantitatively evaluate seismic waveforms, we used a simple fitting function of Bte(-At), where A and B are calculated using the least-squares method. Using 155 known events occurred in and around the Korean peninsula from the year 2002 to 2005, we found a linear relationship between log(B) and log(Delta), log(Delta) = -0.5799 log(B) + 1.4596. The appropriate size of time window to analyze waveforms is found to be two seconds. Comparison of the epicentral distances in logarithmic scale estimated by this study with those by the Korea Meteorological Administration shows that the error range in 93% of the total data used in this study is less than +/- 0.5. Thus, this new method is proved to be a robust tool for a quick estimation of epicentral distances and applicable to an earthquake early warning system.