ARCUS | Arctic Research Consortium of the United States

7th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Anne-Marie LeBlanc
Authors   Anne-Marie LeBlanc, R. Fortier, M. Allard, C. G. Cosma, and S. Buteau
Category   Physical Science
Title   Seismic Cone Penetration Test and Multi-Offset Vertical Seismic Profiling in Permafrost
Affiliation   Géologie et de génie géologique, Université Laval, Sainte-Foy, Qc, Canada

Abstract

High-resolution multi-offset Vertical Seismic Profiling (VSP) was carried out in a permafrost mound near the Inuit community of Umiujaq in Nunavik, Québec, Canada, using a Seismic Cone Penetration Test (SCPT) to study the cryostratigraphy and assess the dynamic properties of warm permafrost. Penetrometer-mounted triaxial accelerometers were used as the VSP receivers in depth and a Swept Impact Seismic Technique (SIST) source generating both compressional and shear waves was moved near the surface following a cross configuration of forty seismic shot point locations 1-m apart surrounding the SCPT. Down to a depth of 24 m below the permafrost base, the cone penetration was stopped at depth interval of 1 m to add a new pushing rod, perform the seismic shots and record the seismic waves propagating down to the receivers. The inversion of travel times of both compressional and shear waves, based on a simultaneous iterative reconstruction technique (SIRT) taking into account the multiple seismic shot points and receiver locations, provided tomographic images of the distribution of seismic velocities in permafrost. The Young's and shear moduli at low strains in the permafrost mound were then calculated from the seismic velocities and the permafrost density measured on core samples. The combination of multi-offset VSP, SCPT, SIST and SIRT for tomographic imaging leaded to new insights in the dynamic properties of permafrost.