11:15 AM - 11:30 AM
[S15-09] Rupture process of the 2022 MW 7.0 Chihshang, Taiwan earthquake
According to the report by Central Weather Bureau (CWB) of Taiwan, the ML 6.83 Chihshang, Taiwan earthquake occurred at 06:44:15 (UTC) on September 18, 2022. The epicenter is in Chihshang town, Taitung County, Taiwan. The reported focal mechanism by different organizations are: CWB (205°, 61.3°, 46.6°); GCMT (201°, 61°, 30°) and USGS (203°, 69°, 25°), indicating a west-dipping direction that is different from the known east-dipping LVF.
To investigate the rupture process of the Chihshang earthquake, we used strong motion waveforms of 14 stations, geodetic data of 36 GNSS stations (Figure 1), and P-wave waveforms of 31 teleseismic stations to perform a joint source inversion. We adopted a two-segment source fault model (Figure 1), which consists of a west-dipping segment and an east-dipping segment. The west-dipping segment (strike: 198°, dip: 60°) is generally consistent with the focal mechanism and the east-dipping segment (strike: 18°, dip: 60°) represents the longitudinal valley fault (LVF). The inversion results showed that the rupture of the mainshock originated from the hypocenter and then it propagated on the west-dipping segment at a speed of 3.2 km/s, and meanwhile it triggered the slip on the east-dipping segment. The rupture lasted about 30 s, releasing a total seismic moment of 5.4×1019 N·m, corresponding to an MW of 7.1. The surface projection of the total slip distribution is shown in Figure 1. The large slips of 3 or 4 meters occurred in the shallow part (< 10 km), which is close to the Yuli fault, on the west-dipping segment; while the small slips of 1 or 2 meters occurred at very shallow part (< 5 km), which is close to the northern end of the Chihshang fault, on the east-dipping LVF.
In conclusion, the rupture process of the Chihshang earthquake demonstrated the existence of a west-dipping fault in southeast Taiwan, which might be part of the west-dipping Central Range Fault (CRF), and the east-dipping LVF was also triggered with small slips during this earthquake.
To investigate the rupture process of the Chihshang earthquake, we used strong motion waveforms of 14 stations, geodetic data of 36 GNSS stations (Figure 1), and P-wave waveforms of 31 teleseismic stations to perform a joint source inversion. We adopted a two-segment source fault model (Figure 1), which consists of a west-dipping segment and an east-dipping segment. The west-dipping segment (strike: 198°, dip: 60°) is generally consistent with the focal mechanism and the east-dipping segment (strike: 18°, dip: 60°) represents the longitudinal valley fault (LVF). The inversion results showed that the rupture of the mainshock originated from the hypocenter and then it propagated on the west-dipping segment at a speed of 3.2 km/s, and meanwhile it triggered the slip on the east-dipping segment. The rupture lasted about 30 s, releasing a total seismic moment of 5.4×1019 N·m, corresponding to an MW of 7.1. The surface projection of the total slip distribution is shown in Figure 1. The large slips of 3 or 4 meters occurred in the shallow part (< 10 km), which is close to the Yuli fault, on the west-dipping segment; while the small slips of 1 or 2 meters occurred at very shallow part (< 5 km), which is close to the northern end of the Chihshang fault, on the east-dipping LVF.
In conclusion, the rupture process of the Chihshang earthquake demonstrated the existence of a west-dipping fault in southeast Taiwan, which might be part of the west-dipping Central Range Fault (CRF), and the east-dipping LVF was also triggered with small slips during this earthquake.