Preliminary Analysis of Distributed Acoustic Sensing at the Kafadar Commons Geophysical Laboratory

Date: 4/24/2019

Time: 06:00 PM

Room: Fifth Avenue

The Kafadar Commons geophysical lab located centrally on the Colorado School of Mines campus was created to inspire and provide geophysics students with known buried targets including UXO, archaeological walls, and a dipping concrete wall, among others. Additionally, about 1 km of fiber-optic cable was buried in an approximate rectangular shape of 30m by 90m. For the distributed acoustic sensing (DAS) recording we use an OptaSense ODH3.1 interrogator unit. Ambient recordings began approximately on November 27, 2018 and have continued through January 8, 2019, with some intermittent downtimes. During this time, a local earthquake sequence in Glenwood Springs (~100 miles west of the Mines campus) was recorded, and hammer-source seismic surveys with collocated geophones have been acquired.

We will present the DAS data processing, geometry assignment, and 3D visualizations of both the active and passive data collected thus far, and the feasibility of surface-wave analysis. Data processing includes bandpass filtering in several frequency ranges and despiking. Frequency-band data can be used to analyze different seismic events (from teleseismic to near-surface seismic reflection data). We use two approaches for geometry assignment. The first is the analysis of the recorded data from vehicular/pedestrian traffic, and localizing the rotation points of the cable. The second uses hammer tap-test recordings. Visualizations in 3D will provide an intuitive representation of how observed wavefields are traveling across the DAS array through time. We will also present preliminary results of using an outlier-detecting algorithm to identify these events automatically.

Presenting Author: Whitney J. Trainor

Authors