Marine Sediment Characterized by Ocean‐Bottom Fiber‐Optic Seismology

Autor: Masanao Shinohara, Zack Spica, Takeshi Akuhara, Kiwamu Nishida, Tomoaki Yamada, François Pétrélis
Přispěvatelé: Department of Earth and Environmental Sciences [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Earthquake Research Institute [Tokyo], The University of Tokyo (UTokyo), Physique Non-Linéaire, Laboratoire de physique de l'ENS - ENS Paris (LPENS), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Japan Meteorological Agency (JMA), Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Zdroj: Geophysical Research Letters
Geophysical Research Letters, American Geophysical Union, 2020, 47 (16), ⟨10.1029/2020GL088360⟩
ISSN: 0094-8276
1944-8007
Popis: International audience; The Sanriku ocean-bottom seismometer system uses an optical fiber cable to guarantee real-time observations at the seafloor. A dark fiber connected to a Distributed Acoustic Sensing (DAS) interrogator converted the cable in an array of 19,000 seismic sensors. We use these measurements to constrain the velocity structure under a section of the cable. Our analysis relies on 24 hr of ambient seismic field recordings. We obtain a high-resolution 2-D shear-wave velocity profile by inverting multimode dispersion curves extracted from frequency-wave number analysis. We also produce a reflection image from autocorrelations of ambient seismic field, highlighting strong impedance contrasts at the interface between the sedimentary layers and the basement. In addition, earthquake wavefield analysis and modeling help to further constrain the sediment properties under the cable. Our results show for the first time that ocean-bottom DAS can produce detailed images of the subsurface, opening new opportunities for cost-effective ocean-bottom imaging in the future. Plain Language Summary Distributed Acoustic Sensing (DAS) is a relatively new measurement method that has the potential to convert existing fiber optic communication infrastructure into arrays of thousands of seismic sensors. In this research, we connected a DAS to a cable that was originally installed at the bottom of the ocean to sustain a seismic and tsunami observatory in the Sanriku Region. We show that this new type of measurement can provide reliable information to image and explore the shallow subsurface under this fiber cable. This is the first time such analysis is performed in an oceanic environment, and our methods could be readily exportable to other fiber-optic cables that are the backbones of our modern telecommunication.
Databáze: OpenAIRE
Externí odkaz: