Geophysical monitoring applications for distributed acoustic sensing
31. Mai 2021
Vortragender: Prof. Dr. Jan Dettmer, Department of Geoscience, University of Calgary
Uhrzeit: 16:15
Abstract:
Distributed acoustic sensing is a recent technology that measures the
deformation of a fibre-optic cable with a precise laser instrument. A laser
pulse is transmitted into the optical fibre, where impurities cause Rayleigh
backscattering of a small portion of the light. The timing of this
backscattering is measured by a precise interferometric system. These phase
measurements can be related to locations where changes in axial strain along
the cable occur, which cause changes to the cable length. Therefore, the
entire optical fibre acts as an array of seismic sensors, improving the spatial
resolution in comparison to typical point-based sensors (e.g., geophones) and
leading to improved spatial sampling of seismic waves. In addition, DAS can
measure ground motions over extreme frequency bands, profoundly outperforming
traditional seismic sensors (e.g., seismometers). DAS has been extensively
used for tight oil and gas applications and monitoring of linear assets (e.g.,
pipelines, borders). Geophysical monitoring in other areas is of increasing
interest. Our research interests include seismic monitoring of earthquake and
ambient noise signals. I will be presenting examples from three areas of
application: (1) The monitoring of the Mt. Meager volcanic complex in British
Columbia. (2) Inferring the shallow-most shear-wave velocity structure from
Rayleigh-wave data at a Carbon Capture and Storage research station near
Brooks, Alberta. (3) The monitoring of active and inactive tailings dams at a
northern location in Canada.