← Back to Gallery

Session: Exploring the Frontier of Environmental Processes using Fiber-optic Sensing [Poster]

Type: Poster

Date: 10/9/2024

Time: 07:00 AM

Room: Stanley Park Ballroom

DAS Observations of Ice-Wedge Cracking in Utqiagvik, Alaska

Ice wedge polygons are among the most distinctive landforms in permafrost regions. Conceptually, they form when freezing ground undergoes thermal contraction cracking during winter, followed by crack filling during the spring snowmelt. However, there is a lack of field observations hindering the understanding of cracking dynamics. In this study, we report over two thousand strong seismic signals throughout the winter months identified in the continuous recordings of yearly-deployed distributed acoustic sensing (DAS) system. These signals are characterized as short-duration events, with center frequencies ranging from 5 to 30 Hz. The events present body wave arrivals closely followed by surface waves, indicating a source near the installed fiber. We found a strong correlation between the daily occurrence of these events and periods of extremely low ground temperatures. Consequently, we interpret these events as cryoseisms originating from the permafrost. During periods of intense cold, thermal stress within the frozen ground can induce tensional fracturing, resulting in the sudden release of stress in the form of seismic waves, known as frost quakes. Through analysis of each event's moveout, we were able to distinguish the relative source locations. Our findings reveal distinct seismicity patterns between wet tundra and dry tundra environments. Finally, we modeled elastic wave propagation to examine the source mechanisms and compared several potential mechanisms for generating local seismicity within the permafrost with the observed waveforms. This research presents an innovative method by using DAS for monitoring and analyzing the dynamics of thermally fracturing frozen ground in the changing Arctic environment.

Presenting Author: Gabriel

Additional Authors