[SCG58-P34] Long-Term Activity Changes of Very Low Frequency Earthquakes in the Ryukyu Trench
Keywords:very low frequency earthquake, Ryukyu Trench, seismicity
As a result, the activity of the VLFE in the Yaeyama Islands has been gradually decreasing since 2002. In the Yaeyama Islands, a series of MJ 7.0 (March 26, 2002) and MJ 6.9 (March 31, 2002) inter-plate earthquakes occurred in 2002, and seismic activity with magnitudes of 6.0 or more temporarily increased in 2002. The changes in the regular earthquakes activity and VLFE activity would reflect the process in which the strain in the plate interface is temporarily partially released due to the change in the coupling rate at the plate interface in the southwestern part of the Ryukyu Trench.
On the other hand, in the vicinity of Okinawa Island, the activity of the VLFEs has been rapidly increasing since 2015. On the other hand, there was no increase in activities around Amami-Oshima Island during this period. During this period, earthquake swarms occurred in the subducting slab near the trench axis of the central Ryukyu Trench. This suggests that the change of the activity of the VLFEs and seismicity would reflect the release of the strain with the progress of the slow earthquake on the plate interface.