[SSS13-P11] Seismic observation on northern Ryukyu Trench subduction zone
Keywords:The Ryukyu Trench, Seismicity, Philippine Sea Plate
In FY2016, we have conducted a passive source observation in the northern Ryukyu forearc region. We have deployed 47 seismic stations including 43 ocean bottom seismographs (OBS) and 4 onshore stations. All OBSs are equipped with short period (4.5 Hz) geophones. Onshore stations are deployed at Tanegashima (two stations), Nakanoshima, and Akuseki-Jima, composed of broadband and/or 2 Hz seismometers. The average separation of seismic network is about 30 km, and covered the area of 250 km and 160 km in trench parallel and normal directions, respectively. The observation period of OBS is about 4 months, from September to December 2016. From the continuous seismic record, we have detected more than three-times the number of events identified from Japan Meteorological Agency (JMA) catalogue. We also confirmed that almost all our seismic stations recorded the seismic signal when the JMA magnitude of event located within our network is larger than 2.5. In this presentation, we will show the preliminary result of hypocenter relocation analysis.