2:45 PM - 3:00 PM
[SSS05-05] On high-frequency energy release by aftershocks of several inland large earthquakes in Japan
Keywords:aftershocks, high-frequency energy release, Hi-net, realtime aftershock forecasting
The estimated cumulative energy normalized by their mainshock energy distributes from 0.017 to 1.37. This normalized cumulative energy (NCE) does not show clear dependence on the mainshock energy. NCE represents relative productivity of aftershocks: the aftershock activity is closer to “swarm” type rather than “mainshock-aftershock” type when NCE is larger. Among the analyzed 8 events, the 2004 Chuetsu earthquake is the only case whose NCE exceeds 1, which means the energy released by its aftershocks exceeds the energy released by the mainshock. As expected from the Omori-Utsu law, amount of energy release is larger at earlier lapse times. By the first 1 hour after the mainshock, 9 % to 73 % of the aftershock energy released within 7 days is released. This percentage becomes 10 % to 79 % and 28 % to 96 % by the lapse times of the first 3 hours and 6 hours, respectively. For 5 of the 8 analyzed events, more than half of the 7 days’ aftershock energy is released within the first 6 hours. This result strongly suggests that using energy release by aftershocks within the first several hours is essential to improve the method of aftershock forecasting.