Research on local magnitude (M L ) scale in and near the Korean Peninsula

Abstract

After synthesizing Wood-Anderson seismograms from broadband recordings at FDSN stations (BJT, SSE, INC and MDJ) in and near Korea, the empirical equations, for the vertical and horizontal components, respectively, for determination of local magnitude (M L ) in and near Korea, were estimated through a process of regression. Around 200 data, from events with epicentral distance ?D) ranging from 50 km to 1000 km, measured from synthetic Wood-Anderson seismograms were used. According to the regression with the constraint that the magnitude for an amplitude of 0.001 m measured at epicentral distance of 100 km is 3, the empirical formula (log 10 A 0 ) for the horizontal components is, with standard deviation (s) of 0.52, M L = log 10 A(D) + 1.71 log 10 A 0 (D) – 0.42 + C, and that for the vertical components is, with standard deviation (s) of 0.56, M L = log 10 A(D) +1.70 log 10 A 0 (D) – 0.4 + C, where, C is a station correction factor and A is the amplitude. This result shows that the attenuation in and near Korea is stronger than that in the East United States (Kim, 1998) and weaker than that in South California (Kanamori et al., 1993).