NX-2G: Autonomous BBOBS-NX for a highly mobile broadband seismic and tilt observation at the seafloor

Developments of the broadband ocean bottom seismometer (BBOBS) and its new generation system (BBOBSNX) have been a base to establish the ocean floor broadband seismology, since 1999. Our BBOBS and BBOBS-NX data is adequate for modern broadband seismic analyses to study the deep Earth interior. Especially, the BBOBS-NX can offer the low noise horizontal data comparable to land seismic stations in periods longer than 10 s. As a variation of the BBOBS-NX, the BBOBST-NX has been developed too, which enables the additional tilt measurement at the seafloor with the broadband seismic data. Their high performance can be a breakthrough to realize the geodetic observation network at the seafloor for slow slip event observations for example. A defect of the current BBOBS-NX system is necessity of the submersible vehicle in its operation of the deployment and the recovery. This condition limits possibilities of observations, compared to observations by the BBOBS that can be operated even on a small fishery boat. The development of the autonomous BBOBS-NX, NX-2G, is really required to elucidate the Earth interior below wide oceanic area in the future.