초동 P파를 이용한 조기 규모추정에 관한 연구

The study on rapid magnitude estimation using first arrival

We have been conducting several studies on providing information to the public promptly as soon as earthquake occurs. Recently, JMA proposed a method for warning big earthquakes by observing the first 2 seconds after the first arrival. In this study, the envelope of the absolute value of the first 2 seconds after the first arrival is calculated, and then the relation of epicentral distance and slope of envelope, parameter B, is obtained. This result is applied to local magnitude equation of KMA, which then gives us a new magnitude equation from which can estimate the magnitude using maximum amplitude of P wave. We applied the method to two recent earthquakes; Uljin and Daegu. The results using only the vertical components show that the magnitudes are lower than those calculated by the local magnitude equation of KMA. However, when we apply the method to the 3 components of maximum displacements, the results corresponds with those obtained from the local magnitude equation.