10:45 AM - 11:05 AM
[MIS34-06] Strong motion and source processes of the 2016 Kumamoto earthquake sequence
Keywords: the 2016 Kumamoto earthquake, strong motion, source process
KiK-net Mashiki (KMMH16) recorded PGA more than 1000 gal, and ground motions were observed wider area for the 7.3 event than the M6.5 event. PGAs and PGVs of K-NET/KiK-net stations are consistent with the empirical attenuation relationship of Si and Midorikawa (1999). PGVs at longer distance than 200 km attenuate slowly, indicating the effect of Lg wave of western Japan. 5% pSv of the Mashiki town in Kumamoto shows a peak of 1-2 s that exceeds ground motion response of JR Takatori of the 1995 Kobe earthquake and the Kawaguchi town in Niigata of the 2004 Chuetsu earthquake. KiK-net Mashiki that locates 640 m apart from the Mashiki town observed large ground motion with a peak of 1 s. 5% pSv of the Nishihara village in Kumamoto shows 350 cm/s peal at 3-4 s. Ground motions at several stations in Oita exceed the attenuation relationship due to a triggered earthquake by the M7.3 event. PGAs of K-NET Yufuin (OIT009) records 90 gal for the M7.3 event and 723 gal for the near-by triggered event.
Source processes are analyzed using 16 and 27 K-NET/KiK-net/F-net strong motion stations located within an epicenter distance of 50 km and 100 km for the M6.5 and M7.3 events, respectively. Two pulses are observed at many station for the M6.5 event, and corresponding two slips near the hypocenter with a peak of 0.7 m and at north-northeastern with 0.6 m. As for the M7.3 event, large slip does not inverted for around 5 s after the earthquake initiation, then rupture propagated toward the northeastern shallow part reaching near the caldera of the Aso volcano with large slip with a peak of 4.6 m. The shallow slip is consistent with active fault surveys.