2:30 PM - 2:45 PM
[SCG59-04] Seafloor Crustal Deformation Measurement at the Nanseisyoto Trench
Keywords:Nanseisyoto Trench, Seafloor Crustal Deformation, Interplate Coupling
The four-years measurement revealed a site velocity at RKB, 6+/-22 mm/yr to the south and 2+/-26 mm/yr to the east with respect to GEONET Kamitsushima station on the Amurian Plate. The velocity is significantly different from that at RKA, 35+/-23 mm/yr to the north and 30+/-19 mm/yr to the west Nakamura , indicating difference in interplate coupling beneath the two sites. The crustal deformation field along the Ryukyu Arc is affected by the backarc spreading along the Okinawa Trough [Nishimura et al., 2004], slow-slip events [Nishimura, 2014], and back-slip caused by the interplate coupling. The back-slip rate at RKB is calculated at 24+/-25 mm/yr in a northwest direction relative to stable Amurian Plate, resulting 0-20 % of interplate coupling rate beneath RKB from a forward modeling. The low coupling rate is consistent to an active strain release events, such as slow-slip events, very low frequency earthquakes [Tu et al., 2010], and trust-type earthquakes, around RKB. Our observation demonstrates less strain accumulation caused by plate convergence, in the hanging wall side at RKB. We plan to install a new site on the seafloor about 90 km southwest of RKA site in 2016.
Acknowledgement: This work was partly supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), "Enhancement of societal resiliency against natural disasters" (Funding agency:JST).