Seasonal Change at Shallow Depth in the Permafrost Region of Alaska From Seismic Noise
Description:
The EarthScope Transportable Array and their succeeding network stations in Alaska have provided an excellent opportunity to monitor temporal shallow structural changes. We report our analysis from a simultaneous examination of (1) temperature, (2) vertical seismic data, (3) horizontal seismic data, and (4) wind data that can provide a unique perspective to the seasonally changing shallow process at each station.
Observations at some stations indicate a rapid, massive melting phenomena in the summer that causes a thousandfold increase in horizontal power spectral density (PSD). This rapid rise in horizontal seismic noise typically occurs in July, lasting about 30 days. The initiation of this major melting period does not happen immediately after the surface temperature exceeds 0oC; instead, there is a delay of about a month. After the peak horizontal amplitude is reached, it gradually returns to the pre-melting level. Many stations show that this return occurs by the end of December; some stations, however, require until March or April to arrive back to their pre-melting level. For all stations, this return occurs well after the surface temperature becomes negative in September or October. These observations suggest that the melt layer remains at depth as temperatures drop below freezing, perhaps sandwiched between the developing ice from the surface and the underlying permafrost ice. However, we noted some caution is required at a few stations because a transient surge in horizontal amplitudes seems to occur in February and November that appears to be correlated with winds. We summarize the temporal characteristics of individual stations and also the seasonal geographic patterns throughout Alaska.
Session: Monitoring Climate Change With Seismology
Type: Oral
Date: 4/18/2023
Presentation Time: 10:45 AM (local time)
Presenting Author: Toshiro Tanimoto
Student Presenter: No
Invited Presentation:
Authors
Toshiro Tanimoto Presenting Author Corresponding Author toshirotanimoto@ucsb.edu University of California, Santa Barbara |
Aaron Anderson aka@ucsb.edu University of California, Santa Barbara |
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Seasonal Change at Shallow Depth in the Permafrost Region of Alaska From Seismic Noise
Category
Monitoring Climate Change With Seismology