Earthquake magnitude determination using P phase for earthquake early warning

Because reliable short-term earthquake prediction is still not achievable, it is important to identify the onset of potentially disastrous earthquakes and to warn it promptly. In this study, we introduced a method of estimating the magnitude of an earthquake in the earthquake early warning system, being developed and studied worldwide, and applied the method to determine the magnitude of Odaesan earthquake occurred in 20 January 2007. The purpose of earthquake early warning is the provision of timely and effective earthquake information obtained from analyzing seismic P waves. In general, the magnitude of an event is usually estimated by using the period and the amplitude of P waves, which are calculated in real time for prompt analysis. The measured periods and amplitudes are converted to the magnitude scale based on empirical magnitude scaling relationships. Using scaling relationships for northern California, the magnitudes of Odeasan earthquake were estimated to 4.33 +/- 0.96 from the period and 4.70 +/- 0.30 from the amplitude and the averaged magnitude was 4.5, which is close to other studies. Development of magnitude scaling relationships based on seismic records from local earthquakes around the Korean Peninsula would allow to construct stable earthquake early warning system in Korea.