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[SCG61-11] Evaluation crustal stress state in seismic active region using seismic moment efficiency and b-value (3)
Keywords:b-value, seismic activity, seismic moment, temporal variation
Frequency – Magunitude distribution of minor earthquakes ( b-value) has been reported to be indicative stress condition for forthcoming major earthquakes. In addition, recent study suggested that proximity of large earthquake can be evaluated by fault orientation distribution. In this study, we propose the proximity that is evaluated from ratio of stacked seismic moment tensor to total moment release in a volume. The ratio means it might be close to the strength of the medium based on the Mohr diagram and Coulomb failure condition. We considered the change in b-value and the ratio in the focal regions of large earthquakes in the 2016 Kumamoto and 2019 Ridgecrest earthquakes. The large mainshocks over magnitude of 7 were accompanied by a large fore shock and preceding small seismic activity. Specific temporal variations for pre-foreshock, interval between the foreshock and mainshock, and aftershock sequences have been observed. Especially, the proximity between the interval periods are different from it just after the main shocks.