Chapters authored
Seismic Velocity Structure in and around the Japanese Island Arc Derived from Seismic Tomography Including NIED MOWLAS Hi-net and S-net Data
Japanese Islands are composed of four plates, with two oceanic plates subducting beneath the two continental plates. In 2016 the National Research Institute for Earth Science and Disaster Resilience (NIED) Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench (S-net) started seismic observation of the offshore Hokkaido to Boso region in the Pacific Ocean, and Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) was transferred to NIED. We add the NIED S-net and DONET datasets to NIED high-sensitivity seismograph network (Hi-net) and full range seismograph network (F-net) datasets used in the previous study and obtain the three-dimensional seismic velocity structure beneath the Pacific Ocean as well as Japanese Islands. NIED S-net data dramatically improve the resolution beneath the Pacific Ocean at depths of 10–20 km because the seismic stations are located above the earthquakes and on the east side of the Japan Trench. We find a NS high-Vp zone at depths of 20–30 km. The 2018 Eastern Iburi earthquake occurred below the northern part of this high-V zone. The coseismic slip plane of the 2011 Tohoku-oki earthquake has low Vp/Vs, but its large slip region has high Vp. The broad low-Vp/Vs region may play a role in large earthquake occurrence.
Part of the book: Seismic Waves