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Urban Seismic Site Characterization With Fiber-Optic Seismology

Session: Data Fusion and Uncertainty Quantification in Shallow Crust Characterization and Modeling

Type: Oral

Date: 4/19/2021

Presentation Time: 05:00 PM Pacific

Description: 

Accurate ground-motion prediction requires accurate site effect assessment. In urban settings, where such assessments are most important, geotechnical surveys are difficult to perform, which limits their availability. Distributed acoustic sensing (DAS) presents an appealing alternative by repurposing existing fiber-optic cables, which are plentiful in urban environments where they are deployed for telecommunication, as an array of seismic sensors. We present a proof-of-concept demonstration by using DAS to produce high-resolution maps of the shallow subsurface with the Stanford DAS array. We describe new methods, and their assumptions, that allow us to assess the H/V spectral ratio – a technique widely used to estimate the natural frequency of the site, and to extract Rayleigh-wave dispersion curves from the ambient seismic field. These measurements are jointly inverted to provide models of shallow seismic velocities and sediment thicknesses above bedrock. The good agreement with an independent survey validates the methodology and demonstrates the potential of DAS for microzonation.

Presenting Author: Gregory C. Beroza

Student Presenter: No

Authors