Improved moving window cross-spectral analysis for resolving large temporal seismic velocity changes in permafrost

• Published in: Geophysical Research Letters
• Main Authors: James, S. R., Knox, H. A., Abbott, R. E., Screaton, E. J.
• Language: unknown
• Published: 2022
• Subjects: 58 GEOSCIENCES; Arctic; permafrost; Alaska
• Online Access: http://www.osti.gov/servlets/purl/1374826; https://www.osti.gov/biblio/1374826; https://doi.org/10.1002/2016GL072468

Cross correlations of seismic noise can potentially record large changes in subsurface velocity due to permafrost dynamics and be valuable for long-term Arctic monitoring. We applied seismic interferometry, using moving window cross-spectral analysis (MWCS), to 2 years of ambient noise data recorded in central Alaska to investigate whether seismic noise could be used to quantify relative velocity changes due to seasonal active-layer dynamics. The large velocity changes (>75%) between frozen and thawed soil caused prevalent cycle-skipping which made the method unusable in this setting. We developed an improved MWCS procedure which uses a moving reference to measure daily velocity variations that are then accumulated to recover the full seasonal change. This approach reduced cycle-skipping and recovered a seasonal trend that corresponded well with the timing of active-layer freeze and thaw. Lastly, this improvement opens the possibility of measuring large velocity changes by using MWCS and permafrost monitoring by using ambient noise.