Attenuation characteristics of ground motion intensity from earthquakes with intermediate depth

Abstract

Data of the intermediate depth (the Geioyo and the Shizuoka) earthquakes in Japan recorded in a dense network is analysed and compared with various available attenuation relations. The approach of Midorikawa (Midorikawa S., 1993, Technophysics 218, 287–295) based on the empirical Green’s function technique of Irikura (Irikura, K., 1986, Proceedings of the 7th Japan Earthquake Engineering Symposium, pp. 151–156.) has been used to model the rupture responsible for these earthquakes and peak ground acceleration are simulated at selected observation points. The method presented in this work includes the transmission effect in a multiple layer crustal model for a finite fault earthquake source model. Sharp attenuation rate is seen for such intermediate depth earthquakes which is difficult to explain through conventional attenuation relations. Detail study of the methodology and comparison of results shows that the transmission factor plays an important role for the sharp attenuation rate for intermediate-to deep-focus earthquakes.