QUICK AND RELIABLE DETERMINATION OF MAGNITUDE FOR SEISMIC EARLY WARNING

This article reports efforts toward using real-time earthquake monitor ing by the Taiwan Central Weather Bureau to meet the needs of seismic early warning. Twenty-three sets of strong-motion data from moderate e arthquakes (M-L > 5.0) in the Taiwan area are used to demonstrate the feasibility of this goal. For earthquakes larger than M-L 5, epicenter s 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 +/- 0.13. Our results show that the real-time strong-motio n system routinely used by the Central Weather Bureau can be used to d etermine epicenters and magnitudes in about 30 sec after occurrence of earthquakes in Taiwan. Such information hopefully can be used to redu ce damage to society.