Examination of source-model construction methodology for strong ground-motion simulation of multi-segment rupture during 1891 Nobi earthquake

Abstract

We examine the construction methodology of a source model for strong ground-motion prediction of scenario earthquakes with a long active-fault zone including a multi-segment rupture case. For the multi-segment rupture event, different seismic moments are given by applying two different source-model construction methodologies: (1) a methodology based on seismological scaling relationships and (2) a methodology in an active-fault study based on the cascade model (Working Group on California Earthquake Probabilities, 1995). The difference between these methodologies is whether or not a slip of each segment depends on total rupture length. We investigate which construction methodology is more appropriate for the construction of the source model. We use the two methodologies to construct characterized source models for strong ground-motion simulations of the 1891 Nobi earthquake, which was a multi-segment rupture event occurring in the Nobi active-fault system. We evaluate the constructed source models by comparing the seismic intensities obtained from simulated waveforms with those estimated from the questionnaire-based intensities determined by Muramatu and Kominami (1992). The characterized source model constrained by seismological scaling relationships can give a more adequate distribution of the estimated seismic intensities. We also suggest that the Gifu-Ichinomiya fault might be considered as a source fault to explain the damage distribution on the Nobi Plain.

Examination of source fault model for the Gifu-Ichinomiya fault based on seismic intensity data

“…Model A includes the entire Gifu-Ichinomiya fault suggested by the Research Group for Active Faults of Japan (1991). The location of this model is the same as that of the most plausible source model of Kuriyama and Iwata (2011). Although the Gifu-Ichinomiya fault of Model A might be located far from the other faults, it is possible that the rupture could propagate across the 10-km discontinuity, as in the case of the 1668 earthquake in the North Anatolian fault system reported by Kondo (2009).…”

“…In this study, we assume that the questionnaire-based intensity at survey points with a damage ratio of greater than, or equal to, 80% is 7. Here, we also assume that the questionnaire-based intensity is equivalent to the JMA seismic intensity scale, as in the case of Kuriyama and Iwata (2011). Miyakoshi et al (2003) estimated the distribution of the peak ground velocity (hereafter, referred to as PGV) during the 1891 Nobi earthquake.…”

“…For these 7 models, the width of each segment is obtained from the lower cutoff depth of microseismic activity, the depth of the upper limit of the fault plane, and the dip angle assumed for each segment. For the northwestern part of the Nukumi fault (Nukumi segment), the Neodani fault (Neodani segment), and the Umehara fault (Umehara segment), we apply the same geometrical parameters as those used in Kuriyama and Iwata (2011).…”

“…They conducted strong ground motion simulations using an empirical Green's function method (Hartzell, 1978;Irikura, 1986) based on assumed characterized source models (Irikura and Miyake, 2001). Through a comparison of the seismic intensities obtained from simulated waveforms and those estimated from questionnaire-based intensities determined by Muramatu and Kominami (1992) over a wide area, Kuriyama and Iwata (2011) determined the most plausible source-model construction methodology. Furthermore, their results suggested that the GifuIchinomiya fault, which is buried beneath the Nobi Plain, might have ruptured during the 1891 Nobi earthquake.…”

“…1), was one of the greatest inland crustal earthquakes ever recorded in Japan. Kuriyama and Iwata (2011) examined the construction methodology of a source model for strong ground motion prediction of a scenario earthquake for the Nobi earthquake. They conducted strong ground motion simulations using an empirical Green's function method (Hartzell, 1978;Irikura, 1986) based on assumed characterized source models (Irikura and Miyake, 2001).…”