Applicability of source scaling relations for crustal earthquakes to estimation of the ground motions of the 2016 Kumamoto earthquake

Kojiro Irikura,Hiroe Miyake,Kazuhiro Somei,Katsuhiro Kamae,Susumu Kurahashi,Kunikazu Yoshida,Ken Miyakoshi

doi:10.1186/s40623-016-0586-y

Abstract

A two-stage scaling relationship of the source parameters for crustal earthquakes in Japan has previously been constructed, in which source parameters obtained from the results of waveform inversion of strong motion data are combined with parameters estimated based on geological and geomorphological surveys. A three-stage scaling relationship was subsequently developed to extend scaling to crustal earthquakes with magnitudes greater than Mw 7.4. The effectiveness of these scaling relationships was then examined based on the results of waveform inversion of 18 recent crustal earthquakes (Mw 5.4–6.9) that occurred in Japan since the 1995 Hyogo-ken Nanbu earthquake. The 2016 Kumamoto earthquake, with Mw 7.0, was one of the largest earthquakes to occur since dense and accurate strong motion observation networks, such as K-NET and KiK-net, were deployed after the 1995 Hyogo-ken Nanbu earthquake. We examined the applicability of the scaling relationships of the source parameters of crustal earthquakes in Japan to the 2016 Kumamoto earthquake. The rupture area and asperity area were determined based on slip distributions obtained from waveform inversion of the 2016 Kumamoto earthquake observations. We found that the relationship between the rupture area and the seismic moment for the 2016 Kumamoto earthquake follows the second-stage scaling within one standard deviation (σ = 0.14). The ratio of the asperity area to the rupture area for the 2016 Kumamoto earthquake is nearly the same as ratios previously obtained for crustal earthquakes. Furthermore, we simulated the ground motions of this earthquake using a characterized source model consisting of strong motion generation areas (SMGAs) based on the empirical Green’s function (EGF) method. The locations and areas of the SMGAs were determined through comparison between the synthetic ground motions and observed motions. The sizes of the SMGAs were nearly coincident with the asperities with large slip. The synthetic ground motions obtained using the EGF method agree well with the observed motions in terms of acceleration, velocity, and displacement within the frequency range of 0.3–10 Hz. These findings indicate that the 2016 Kumamoto earthquake is a standard event that follows the scaling relationship of crustal earthquakes in Japan.

Highlights

One of the most important factors when predicting strong ground motions is the characterization of source models for future earthquakes
To predict near-source strong motions dominated by shortperiod motions of
The main purpose of this study was to validate whether the scaling relationships of the source parameters for crustal

Summary

Introduction

One of the most important factors when predicting strong ground motions is the characterization of source models for future earthquakes. Fundamental information for the source model comes from source scaling relationships, which control the fault parameters necessary to estimate ground motions. The seismic moments of large earthquakes are estimated primarily from teleseismic data, they are sometimes inferred from geodetic data. Catalogs of source parameters include a variety of qualities, some of which are not always available for strong motion estimation (e.g., Wells and Coppersmith 1994; Stirling et al 2002, 2013). To predict near-source strong motions dominated by shortperiod motions of

Objectives

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Conclusion