Subsurface Imaging With Ocean‐Bottom Distributed Acoustic Sensing and Water Phases Reverberations
Zack Spica, Jorge C. Castellanos, Loïc Viens, Kiwamu Nishida, Takeshi Akuhara, Masanao Shinohara, Tomoaki Yamada
Abstract
Abstract Seismic waves from earthquakes recorded on the seafloor are composed of complex multiple arrivals. Here, distributed acoustic sensing (DAS) observations along a cable located offshore the Sanriku Coast, Japan, show that the local earthquake wavefield is particularly rich in Scholte waves. We introduce a processing pipeline to extract these surface waves from DAS records. We then invert hundreds of dispersion curves along a section of the cable to form a shallow high‐resolution shear‐wave velocity model. Moreover, we focus on the possible generation mechanisms of Scholte waves through a series of 2D and 3D full‐wavefield numerical simulations. We show that water phase reverberations greatly contribute to the generation of Scholte waves on the ocean floor. This study demonstrates the potential of DAS to observe and better understand a poorly known marine wave phenomenon and image the offshore shallow seismic structure with an unprecedented spatial resolution.