[SCG71-P11] A high-resolution seismic image of possible fluid migration pathway associated with the 2011 Tohoku earthquake
Keywords:high-resolution seismic image, fluid migration pathway, Tohoku earthquake
In order to elucidate the fluid behavior along the OOST fault plane, we have carried out geophysical and geochemical investigations in the Tohoku forearc using R/V Shinsei-maru (KS16-17 cruise) in November 2016. During the cruise, we have done: (1) high-resolution seismic imaging by parametric sub-bottom profiler (SBP), (2) seafloor mapping by multi-beam echo-sounder, (3) bottom seawater sampling by CTD sampler, (4) seafloor sediment sampling by multiple corer, and (5) onboard magnetic and gravity observations. We observe a clear seismic reflection image of fault scarp on a high-resolution SBP line near the Site N3 at which the helium isotope anomaly was observed one month after the 2011 Tohoku earthquake. A possible OOST fault is likely to produce tilting structure of the topmost sedimentary layer. Despite low continuity of the reflector, deep crustal multi-channel seismic reflection data exhibit a possible OOST fault plane with reverse polarity reflection upward from deep plate-interface, suggesting the fluid migration along the fault associated with the 2011 Tohoku earthquake. In this paper we will show preliminary results of the cruise KS16-17.