5:15 PM - 7:15 PM
[SSS12-P03] Evaluation of detection capabilities in the JMA catalog associated with introducing the AS-net and seismicity analysis in and around the Mutsu Bay in Aomori prefecture
Keywords:AS-net, JMA catalog, Magnitude of completeness , Seismicity, Mutsu Bay
A high-sensitivity seismic network (AS-net) has been operated around northern Tohoku and southwestern Hokkaido by the Association for the Development of Earthquake Prediction since 2014 (Noguchi et al., 2017). Seismic data recorded by some stations in AS-net has been introduced into the Japan Meteorological Agency unified earthquake catalog (JMA catalog) since December 2017. In this presentation, we report temporal changes in the detection capabilities of the JMA catalog associated with introducing the AS-net in the inland part of Aomori prefecture (dep 0-50km). In addition, the results of a preliminary seismicity analysis regarding seismic activities associated with the M4.6 and M5.1 earthquakes that occurred in Mutsu Bay in November 2024 were also presented.
We evaluated changes in the detection capabilities by calculating the difference of spatiotemporal distributions of the magnitude of completeness Mc in each period before and after introducing the AS-net using the maximum curvature method (Woessner and Wiemer, 2005; Wiemer, 2001). The Mc decreased by 0.3-0.7 on average after installing the AS-net in regions from the Shimokita peninsula to Mutsu Bay in Aomori prefecture. The same analysis was also performed in periods spanning April 2016, when an automatic hypocenter detection method was applied (Tamaribuchi et al., 2016). However, a significant change in Mc was not found in the above regions. This finding implies that installing AS-net plays a significant role in improving the detection capabilities of the JMA catalog in the focused area.
We noticed the aftershock activities following the M4.6 and M5.1 earthquakes in Mutsu Bay in November 2024. The epidemic-type aftershock sequence (ETAS) model (Ogata 1985, 1988, and 1989; Ogata and Tsuruoka, 2015) was applied to the time series after the M4.6 earthquake. The results revealed a typical aftershock decay value (p = 0.95) and characteristics of non-swarm activity. The cumulative number of events predicted by the ETAS parameters obtained in this study was found to fit the subsequent time series. A seismic anomaly such as seismic quiescence is considered not to have occurred in the analyzed region after these M4-5 class events.
We evaluated changes in the detection capabilities by calculating the difference of spatiotemporal distributions of the magnitude of completeness Mc in each period before and after introducing the AS-net using the maximum curvature method (Woessner and Wiemer, 2005; Wiemer, 2001). The Mc decreased by 0.3-0.7 on average after installing the AS-net in regions from the Shimokita peninsula to Mutsu Bay in Aomori prefecture. The same analysis was also performed in periods spanning April 2016, when an automatic hypocenter detection method was applied (Tamaribuchi et al., 2016). However, a significant change in Mc was not found in the above regions. This finding implies that installing AS-net plays a significant role in improving the detection capabilities of the JMA catalog in the focused area.
We noticed the aftershock activities following the M4.6 and M5.1 earthquakes in Mutsu Bay in November 2024. The epidemic-type aftershock sequence (ETAS) model (Ogata 1985, 1988, and 1989; Ogata and Tsuruoka, 2015) was applied to the time series after the M4.6 earthquake. The results revealed a typical aftershock decay value (p = 0.95) and characteristics of non-swarm activity. The cumulative number of events predicted by the ETAS parameters obtained in this study was found to fit the subsequent time series. A seismic anomaly such as seismic quiescence is considered not to have occurred in the analyzed region after these M4-5 class events.