Continuous Long-Term Seafloor Pressure Observation for Detecting Slow-Slip Interplate Events in Miyagi-Oki on the Landward Japan Trench Slope

Abstract

In starting continuous seafloor pressure observation in the Miyagi Oki region, where a M 7.5 interplate earthquake is expected within the next three decades, we distributed pressure stations to enable us to determine slow-slip event size and location along the top of the subducting Pacific Plate as precisely as possible. Numerical simulation indicated that ∼ 2 cm uplift is expected above a thrust faulting event of Mw=6.8 at a depth of ∼ 40 km. Combining continuous onshore global positioning system (GPS) time series and seafloor pressure observation is expected to significantly improve spatial resolution of interplate slip distribution over inversion results using only GPS data alone. Pressure change due to the predicted amount of seafloor movement is comparable to or slightly less than that caused by dynamic ocean processes. Seafloor pressure data from long-term continuous observation using the spatially dense array provided by our study is invaluable for understanding spatiotemporal patterns in seafloor pressure variations caused by two different origins – the lithosphere and the hydro-atmosphere.