Joint Inversion of MASW and Ambient-noise HVSR Data for Estimating Shear Wave Velocity Profile in Warm Permafrost: A Case Study at Northway Airport, Alaska
Description:
The study aims to investigate the impacts of permafrost degradation on shear wave velocity and seismic response of warm permafrost sites. A joint dataset, combining Multichannel Analysis of Surface Waves (MASW) and Horizontal-to-Vertical Spectral Ratio (HVSR) analysis of ambient noise acquired at Northway Airport, Alaska, was utilized to delineate the permafrost table and shear wave velocity profiles. MASW data acquisition involved deploying 24-channel vertical geophones (4.5 Hz) spaced 3.0 m apart and connected to a data recorder. Seismic signals were generated using a sledgehammer striking a plate, with five stacked two-second seismograms recorded per location at offsets of 3.0 m and 4.6 m on both sides of the array. Surface wave dispersion characteristics were analyzed to extract phase velocity data in the 5–18 Hz frequency range. In parallel, three hours of ambient noise data were recorded using a three-component broadband velocity sensor. The data were band-pass filtered (3–70 Hz) and segmented into 180 one-minute windows. HVSR values for each segment were computed in the 4–18 Hz frequency range by taking the ratio of the geometric mean of the horizontal components (NS and EW) to the vertical component. Median HVSR and its standard deviations were evaluated assuming a lognormal distribution. Joint inversion was performed using Monte Carlo sampling to integrate the HVSR and MASW datasets. The inversion process utilized an initial 1D layered earth model from previous geotechnical reports, iteratively refining parameters such as layer thickness, shear and compressional wave velocity, density, and Poisson’s ratio. The computed HVSR and dispersion curves were compared against their respective observed values during each iteration to minimize the least-squares error between them. The final model from inversion reveals significant insights into the shear wave velocity structure of warm permafrost sites and the impact of permafrost degradation on seismic site responses and provides a robust framework for assessing seismic hazards in the permafrost-affected areas undergoing degradation due to climate change,
Session: Geophysics in a Changing World: Monitoring Applications from Seismology and Beyond [Poster]
Type: Poster
Date: 4/15/2025
Presentation Time: 08:00 AM (local time)
Presenting Author: Utpal
Student Presenter: No
Invited Presentation:
Poster Number: 48
Authors
Utpal Dutta Presenting Author Corresponding Author udutta2@alaska.edu University of Alaska Anchorage |
Yue Zhao yzhao8@alaska.edu University of Alaska Anchorage |
Zhaohui (Joey) Yang zyang2@alaska.edu University of Alaska Anchorage |
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Joint Inversion of MASW and Ambient-noise HVSR Data for Estimating Shear Wave Velocity Profile in Warm Permafrost: A Case Study at Northway Airport, Alaska
Session
Geophysics in a Changing World: Monitoring Applications from Seismology and Beyond