9:30 AM - 9:45 AM
[STT18-03] Effect of stress and fluid pressure change on shallow earthquake swarm induced by the 2011 Tohoku-Oki earthquake inferred from dense seismic observation
Keywords:The 2011 Tohoku-Oki earthquake, Induced earthquake, stress, fluid pressure, focal mechanism
For understanding more details of the induced earthquake swarm and its causes, we deploy dense seismic observation networks in three areas: southern Akita, northern Akita, Fukushima (Aizu) -Yamagata [cf. Hirahara et al., 2015, AGU Fall Meeting]. Station separation is less than a couple of kilometers in southern Akita, and about 5 kilometers in northern Akita and Fukushima-Yamagata areas. Seismometers and data loggers deployed are KVS-300 and EDR-X7000 of Kinkei System Corporation, respectively.
By using data from the dense seismic network, we can determine reliable focal mechanisms even for M~1 earthquakes. Focal depths of most of earthquakes are determined to be a few kilometers shallower than JMA catalog depths. The improvements of hypocenter locations and focal mechanisms will enable us to estimate the stress regime and the fluid pressure in Tohoku district in more details.
This study was conducted with the support of the Grant-in-Aid for Scientific Research on Innovative Areas (Crustal Dynamics, KAKENHI No. 26109002) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. This study was also supported by the MEXT under its Earthquake and Volcano Hazards Observation and Research Program. Dr. Takahiro Shi’ina, Dr. Keisuke Yoshida, and Mr. Yukihiko Chiba helped us for the observation.