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Antarctic Icequakes Shed Light on the Applicability of DAS for Microseismic Monitoring

Session: Fiber-Optic Seismology I

Type: Oral

Date: 4/23/2021

Presentation Time: 10:00 AM Pacific

Description: 

Microseismic monitoring has applications in a wide range of environmental and industrial settings. Although contexts vary, the instrumentation and data analysis techniques are generally universally applicable. This study shows how Distributed Acoustic Sensing (DAS) methods used to study basal icequakes (earthquakes in ice) can be applied to microseismic monitoring for Carbon Capture and Storage (CCS) projects under the ACT DigiMon project.

For the first time in the Antarctic, we explore the use of DAS as a new approach to study icequakes. These icequakes offer insight into how the ice slides over the glacier bed and can be used to image the internal ice column structure. A fibre-optic cable was deployed on the ice surface at Rutford Ice Stream in a linear and triangular configuration, with data recorded using a 1kHz sampling rate with a 10m gauge length. We compare the performance of DAS with a conventional geophone network for: microseismic detection and location; source mechanism inversion; and seismic anisotropy. For microseismic detection, we compare migration and radon transform methods. Radon transform methods exploit the spatial resolution of DAS and provide a robust method to identify arrivals. This approach significantly increases the number of events detected by the DAS network, compared to standard migration methods. Compared to the geophone network, the linear DAS array has a much higher detection rate while fewer events are identified with the triangular array due to its smaller spatial extent. Full-waveform source mechanism inversions using DAS successfully constrain the horizontal stick-slip nature of the icequakes. Furthermore, we demonstrate that the 2D DAS array can successfully measure the seismic anisotropy of the ice fabric.

The methodology and implications of this work are relevant for employing DAS for microseismic detection, source and path analysis elsewhere, such as at CCS projects.

Presenting Author: Anna L. Stork

Student Presenter: No

Authors