Yih-Min Wu, Tzay-Chyn Shin, and Yi-Ben Tsai
Quick and reliable determination of magnitude for seismic early warning
Bulletin of the Seismological Society of America (October 1998), 88(5):1254-1259

Abstract:
This article reports efforts toward using real-time earthquake monitoring by the Taiwan Central Weather Bureau to meet the needs to seismic early warning. Twenty-three sets of strong-motion data from moderate earthquakes (M _L >5.0) in the Taiwan area are used to demonstrate the feasibility of this goal. For earthquakes larger than M _L 5, epicenters can be reliably determined in about 15 sec after the arrival of the P wave at the nearest station. The earthquake magnitude M _L cannot be determined in the same time frame due to incomplete recording of shear waves at some stations. However, the magnitude based on the first 10 sec of signal (M _L10 ) can be related to M _L as follows: M _L = 1.28 * M _L10 -0.85+ or -0.13. Our results show that the real-time strong-motion system routinely used by the Central Weather Bureau can be used to determine epicenters and magnitudes in about 30 sec after occurrence of earthquakes in Taiwan. Such information hopefully can be used to reduce damage to society.