The Influence of Environmental Microseismicity on Detection and Interpretation of Small-Magnitude Events in a Polar Glacier Setting

Session: Environmental and Near Surface Seismology: From Glaciers and Rivers to Engineered Structures and Beyond [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Glacial environments exhibit temporally variable microseismicity. To investigate how this microseismicity influences event detection, we process 14 months of seismic data collected from the Taylor Glacier terminus in Antarctica, with two noise adaptive digital power detectors. We perform waveform infusion experiments to test reliable detection magnitudes on certain days and compare these against magnitudes predicted from an analytical ice crack source model. We find that environmental microseismicity regulates detector capability to detect seismic events with source size comparable to thermal penetration depths. Under certain conditions, we can interpret measured seismicity changes as `true' seismicity changes, rather than changes in detector capability. In general, one detector also outperforms the other: it identifies more events and shows a more prominent summertime diurnal signal, while maintaining a higher detection capability. We conclude that real physical processes are responsible for the summertime diurnal component of the inter-detector difference. While one detector identifies this process as environmental microseismicity, the other detector identifies it as elevated waveform activity. Our analysis provides a means for minimizing detection biases and estimating source sizes when interpreting temporal seismicity patterns to better infer seismogenic processes in glacial or other environments with temporally variable microseismicity.

Presenting Author: Joshua D. Carmichael

Authors