12:25 PM - 12:40 PM
[SCG65-12] Strong motion simulation for the 2014 Northern Nagano Prefecture earthquake based on the pseudo point-source m
Keywords:the pseudo point-source model, the 2014 Northern Nagano Prefecture earthquake, strong ground motion, omega-square model, Fourier phase
If such a simplified source model can explain strong ground motions with certain accuracy, it would be helpful in reducing costs for strong motion prediction especially a large number of scenarios are considered. Moreover, according to the results of past studies, the model can explain strong ground motions from a mega-thrust earthquake (Nozu, 2012) and an intraslub earthquake (Nagasaka et al., 2014), sometimes better than the conventional characterized source models.
Its applicability to short distances, however, could be restricted, because it is expressing the subevent with a point. Therefore, its applicability to shallow crustal earthquakes should carefully be examined by using observed records.
The examination of the applicability of the model to shallow crustal earthquakes has already been started (e.g., Hata and Nozu, 2012). In this study, a pseudo point-source model was developed for the 2014 Northern Nagano Prefecture earthquake and strong ground motions were simulated based on the model. The selected parameters are as follows: number of subevents=1, longitude=137.901, latitude=36.722, depth=4.6 km, seismic moment=2.0E+18 Nm, corner frequency=0.25 Hz. A medium density of 2.7×103 kg/m3 and a shear wave velocity of 3.5 km/s were assumed. The mean value of 0.63 was used for the radiation coefficient. Another mean value of 0.71 was used for PRTITN (Boore, 1983), which is a coefficient indicating the partition of energy into two horizontal components. The Q value estimated in a past study (Satoh and Tatsumi, 2002) was used to represent the path effects. Records of the November 23, 12:46 aftershock were used to evaluate the Fourier phase. According to the results, the pseudo point-source model generally can explain strong ground motions around the source region fairly well, although there is still a room for future improvement (The figure shows the results for the velocity waveforms and the Fourier spectra at NGN002, NGN005 and NGN007).
Acknowledgement: Strong motion data used in this study were kindly provided by the NIED.