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Seismic Array Analysis Using Fiber-Optic Distributed Acoustic Sensing on Small Local and Regional Earthquakes

Session: Fiber-Optic Seismology II [Poster]

Type: Poster

Date: 4/23/2021

Presentation Time: 03:45 PM Pacific

Description: 

Seismic array beamforming analysis is used to measure signal features including the wave propagation slowness vector (i.e.,apparent horizontal velocity and back-azimuth). We compare the array analysis of several small local to regional distance earthquakes using both fiber-optic distributed acoustic sensing (DAS) and nodal geophone array collected in northern Nevada from the PoroTomo experiment (e.g., Feigl et al., 2020). The DAS improves seismic array analysis by reducing spatial aliasing due to the dense sampling of the wavefield. One challenge in working with DAS as a seismic array is with the orientation of the cable with respect to the incoming seismic wave. Traditional seismic array stacking and beamforming is successful due to the high coherency of the waveforms between sensors with a consistent orientation typically all vertical components. Alignment of the waveform phase between receivers is therefore a simple function of the horizontal slowness vector. A bend in the fiber-optic cable will add an unknown phase changes that would require corrections before array stacking. We use a technique that only uses phase differences along linear parts of the fiber-optic cable with the highest correlation to measure the slowness vector in two different directions and compare the result with the traditional array beamforming method estimated from the co-located nodal array. Prepared by LLNL under Contract DE-AC52-07NA27344. Release number LLNL-ABS-818339.

Presenting Author: Gene A. Ichinose

Student Presenter: No

Authors