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2-D Shear-Wave Velocity Profile of Shallow Sediments Using Ocean Bottom Distributed Acoustic Sensing and Ambient Noise Probabilistic Inversion

Ambient noise tomography is a well-established technique that estimates the physical properties (i.e., thickness and shear-wave velocity) of the crust and upper mantle through the inversion of surface-wave dispersion curves. Imaging the shallow crust and sediment layers can be difficult, especially offshore, due to the limited number of ocean bottom seismometers. A more accurate sediment mapping on the continental shelf can help identify potential risks like underwater landslides that could damage telecommunication cables or trigger tsunamis. The recent development of the Distributed Acoustic Sensing (DAS) technology presents an opportunity to achieve higher-resolution imaging of the offshore sub-surface using dense station spacing distributed along a fiber-optic cable. We probed 50 km of a telecommunication fiber deployed offshore Cordova, Southern Alaska, and recorded continuous data for four months in 2022. The sediment cover on the continental shelf is likely to have a significant portion of glacial sediments originating from the Copper River, which is situated a few miles to the south. Although no large earthquake (Mw>7.0) has occurred in the region since the 1964 M9.2 Prince William earthquake, the area remains seismically active and susceptible to underwater landslides. We use the data collected from May 04 to May 15, 2022, to compute cross-correlation functions between station pairs along the fiber. From a frequency-time analysis, we estimate surface-wave phase velocity between groups of station pairs and invert to produce a 2-D shear wave velocity profile. In this work, we propose to use a Bayesian Monte Carlo inversion framework to build our final velocity profile. The inverted shallow velocity profile provides new constraints on the nature of the sediments in this seismically active region. We will discuss the implications in terms of sediment transport and mixing but also the potential of underwater landslides associated with these sediments.

Session: Advancing Seismology with Distributed Fiber Optic Sensing [Poster Session]

Type: Poster

Room: Exhibit Hall

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Walid Ben Mansour

Student Presenter: No

Additional Authors