Abstract
In conjunction with the development of a LNG storage tank facility in Fairbanks, Alaska a geotechnical investigation and probabilistic seismic hazard analysis (PSHA) was performed. The site is located within a region in Fairbanks where warm permafrost soils exist (-1°C average soil temperature at depth). In support of the PSHA, field work included vertical shear wave velocity profiling using surface to down hole measurements and multichannel analysis of shear wave velocity (MASW) geophysical techniques. Shear wave velocity measurements suggested that the site be classified as a Seismic Site Class B to C, despite the fact that the soil temperature was just below freezing. A discussion of the PSHA, Fairbanks seismicity is provided. However, because very few shear wave velocity profiles have been developed in warm permafrost, the discussion of the results and how they compare to other studies in Fairbanks shows the unique nature of seismic site response evaluations in warm permafrost regions. LNG facilities are increasing in presence in the Arctic as natural gas is extracted and taken to market. Regions with high seismicity and permafrost soils will have to consider the effects of frozen soils on these facilities during seismic events. This study offers an understanding of those effects and provides insight into site-specific effects of permafrost on a probabilistic seismic hazard analysis.
