Explosion Yield Estimation by Distributed Acoustic Sensing: Insights from the Source Physics Experiments

Session: Explosion Seismology Advances [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

We apply the coda duration magnitude measurement methodology to fiber-optic based Distributed Acoustic Sensing (DAS) observations of chemical explosions from the Source Physics Experiments (SPE). Phase I of SPE took place in granitic rock in southern Nevada. Phase II studied explosions in a dry, alluvium geology (DAG). The magnitude estimates of the events are then used to infer explosive yield of the known chemical explosions of SPE. Duration-derived magnitudes have been in wide use for decades and are a standard reported magnitude for local network operators. The duration-derived approach to magnitude determination is attractive since it is less dependent on absolute amplitude calibration of the sensor and relies on durations between a first arriving wave and a time related to where the signal amplitude falls below some threshold. This approach to magnitude estimation is well-suited for a DAS array, where absolute amplitude calibrations are dependent on many factors including coupling and cable design. Therefore, a duration-based approach to magnitude estimation that is less dependent on unknown site and emplacement effects may be preferable. Available data includes measurements of SPE-3 made from an existing telecom fiber and from a trenched fiber and measurements of three DAG events using both a borehole and surface deployed helical fiber. We first relate the observed coda durations obtained from narrow-band filtered coda envelopes to explosive yield and then predict the explosive yield of another chemical explosion using the relationship. The predicted yield is in general agreement with the experimental value. Finally, we comment on transportability of the approach to explosive yield estimation considering that one of the explosions was emplaced in hard-rock (granite) and the other soft-rock (alluvium).

Presenting Author: Sean R. Ford

Authors