Modeling of strong motion generation areas of the Niigata, Japan, earthquake of 2007 using modified semi-empirical technique

Abstract

The Niigata prefecture in Japan was devastated by a large shallow earthquake (M w 6.6, M JMA 6.8) on July 16, 2007. This earthquake has been recorded at 305 stations of Kiban Kyoshin network (KiK-net). Source model of this earthquake has been computed from accelerograms recorded by KiK-net at near-field stations surrounding source of earthquake. Several isolated wave packets were seen in recorded accelerograms at near-field stations surrounding source of this earthquake. Each wave packet in recorded accelerogram represents an isolated patch of envelope of accelerogram released from a rupture plane and is considered to be an independent source of strong motion generation area. Three different isolated wave packets have been identified within the rupture plane of the Niigata earthquake from recorded accelerograms. These isolated wave packets were considered as strong motion generation areas (SMGAs) in the rupture plane. Source parameters of each SMGA were calculated from the source displacement spectra. The approximate locations of SMGAs over the source fault were estimated using spatio-temporal variation of 48 aftershocks recorded by KiK-net and K-NET. Modified semi-empirical method has been used to simulate strong ground motion at various stations. Comparison of the observed and simulated acceleration waveforms is made in terms of root-mean-square error. Comparison of NS and EW component of observed and simulated records at eight stations confirms the suitability of final source model consisting of three SMGAs and efficacy of the modified semi-empirical technique to simulate strong ground motion.