A Comparison of Approaches To Convert DAS Measurements to Ground Motion
Distributed Acoustic Sensing (DAS), as applied in seismological investigations, measures ground motion as strain or strain-rate averaged over an interval, called the gauge length, along a cable. Traditional seismic measurements are sensitive to ground motion (e.g., velocity or acceleration) at a point rather than a spatially distributed sensitivity. To use DAS data for deriving measurements like earthquake magnitude and explosion yield estimates, using algorithms formulated for traditional ground motion measurements as inputs, it is advantageous to convert strain-based measurements into velocities or accelerations. The theoretical relationship between strain-rate and acceleration, and strain and velocity is well established and has been successfully used to convert DAS measurements in several instances, as strain-rate is proportional to acceleration and strain is proportional to velocity, where the proportionality constant is phase velocity. Strain-rate can also be derived from the spatial derivative of velocity in the direction of the fiber axis. These relationships have been used to derive several algorithms for converting DAS measurements to ground motions including spatial integration, scaling in the f-k domain and measuring moveout velocities for individual phases. While successful conversions of DAS data have been reported in the literature, difficulties have been noted in certain conditions. For example, the f-k approach can produce undesirable low-wavenumber noise, and moveout velocities derived from direct arrivals will not scale later phases correctly. Here we explore how conditions, such as geologic setting and proximity to an explosive source, may complicate relating DAS and traditional seismic measurements by comparing the performance of some of these approaches on synthetic and real DAS data.
Session: Fiber Optic Seismology: Understanding Earth Structure and Dynamics with Distributed Sensors [Poster]
Type: Poster
Room: Evergreen Ballroom
Date: 4/21/2022
Presentation Time: 08:00 AM Pacific
Presenting Author: James T. St. Clair
Student Presenter: No
Additional Authors
James St. Clair Presenting Author Corresponding Author james.stclair@pnnl.gov Pacific Northwest National Laboratory |
Parker Sprinkle parker.sprinkle@pnnl.gov Pacific Northwest National Laboratory |
Kirsten Chojnicki kirsten.chojnick@pnnl.gov Pacific Northwest National Laboratory |
Hunter Knox hunter.knox@pnnl.gov Pacific Northwest National Laboratory |
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A Comparison of Approaches To Convert DAS Measurements to Ground Motion
Category
Fiber Optic Seismology: Understanding Earth Structure and Dynamics with Distributed Sensors
Description