15:30 〜 16:30
[S13-P-17] Dynamic rupture model of the 2014 northern Nagano, central Japan, earthquake
The 2014 northern Nagano, central Japan, earthquake occurred on the northern part of the Kamishiro fault (KF) and the northern extension of KF. The hypocenter is located at the northern end of the KF, and the rupture propagated bilaterally. Surface ruptures intermittently observed along the northern part of KF in the south of the hypocenter (Katsube et al., 2016). Waveform inversion, on the other hand, revealed that large slip mainly distributed in the north of the hypocenter (e.g. Asano et al., 2015). On the northern part of the KF, two M5-class earthquakes recently occurred, thus the slip of the 2014 northern Nagano earthquake could be suppressed. In this study, we construct a dynamic rupture model of the earthquake to understand a mechanism of the earthquake and the present stress condition on the fault.
Our fault model contains two parallel dipping segments and a vertical segment between the two segments, based on the aftershock locations (Imanishi and Uchide, 2015), the analysis of the InSAR data (Yarai, 2015), and the difference between the focal mechanism and the CMT solution. The tectonic stress proportional to depth is modeled, considering the stress inversion result (MEXT et al., 2004). We calculate dynamic rupture processes, assuming a slip-weakening friction law.
When the two dipping segments are under the same stress condition, a rupture initiating on the vertical segment propagates on the two segments simultaneously, and surface slip along the southern segment is larger than the observed one. When the stress drop on the southern segment is less than that on the northern segment, on the other hand, the maximum surface slip along the southern segment is consistent with the observation. The rupture propagates to the southern segment several seconds late, which agrees with the results of waveform inversion. Our simulation results imply that the stress accumulation on the southern segment can be insufficient to rupture because of the past earthquake.
Our fault model contains two parallel dipping segments and a vertical segment between the two segments, based on the aftershock locations (Imanishi and Uchide, 2015), the analysis of the InSAR data (Yarai, 2015), and the difference between the focal mechanism and the CMT solution. The tectonic stress proportional to depth is modeled, considering the stress inversion result (MEXT et al., 2004). We calculate dynamic rupture processes, assuming a slip-weakening friction law.
When the two dipping segments are under the same stress condition, a rupture initiating on the vertical segment propagates on the two segments simultaneously, and surface slip along the southern segment is larger than the observed one. When the stress drop on the southern segment is less than that on the northern segment, on the other hand, the maximum surface slip along the southern segment is consistent with the observation. The rupture propagates to the southern segment several seconds late, which agrees with the results of waveform inversion. Our simulation results imply that the stress accumulation on the southern segment can be insufficient to rupture because of the past earthquake.