Development of Marine Seismic Vibrator towards Realization of Shear Wave Source with No Touch-Down to Seafloor

<jats:title>Abstract</jats:title> <jats:p>We developed a towed marine seismic vibrator (MSV) as a new type marine seismic source that employed the hydraulic servo system for the controllability both in phase and in amplitude of the signal being emitted. MSV could mitigate a risk of the impact to the marine environment while satisfying the necessary condition of seismic sources and could enable shear wave analysis in the marine environment to improve the situation of marine seismic data acquisition. We conducted a sea trial to acquire seismic reflection data using a downsized MSV and a streamer cable above the seafloor where a cabled seismic observatory has been deployed. A series of controlled chirp signals was generated by MSV. The sea trial showed that penetration of seismic signals generated by the downsized MSV was comparable to that by an airgun of 480 cu-inch with a slight inferior signal-to-noise ratio. We could observe the improvement in the penetration of seismic signals for the downsized MSV towed deeper that is preferable to generate shear waves. Finally, we could observe that the amplitude of shear waves, which are reflected back from the subseafloor structure, is acquired by the horizontal components of a seafloor installed seismometer.</jats:p>