Susceptibility to Ground Motion Amplification from Seismic Waves based on Multichannel Analysis of Surface Waves in the Red Deer Area, Alberta

An increase in hydraulic fracturing–related induced seismicity near the city of Red Deer over the recent years has fueled great scientific interest in the area. Most of the research published thus far has focused on the mechanics of the recorded seismic events. The objective of this study is to map the potential susceptibility to ground motion amplification from seismic waves across the study area based on local changes in geology. To achieve this, seven locations were chosen and velocity profiles were created based on multichannel analysis of surface waves (MASW) surveys. This newly acquired geophysical data was incorporated with knowledge of the shallow geology of the Sylvan Lake sub-basin, to assign susceptibility ratings based on the National Earthquake Hazards Reduction Program’s (NEHRP) classification. This analysis demonstrates that areas with a thicker unconsolidated sediment layer above bedrock (areas exhibiting greater depth to top of bedrock) are the most susceptible to the amplification of the seismic ground motions. Conversely, areas where bedrock is at or near the surface show a much lower susceptibility to ground motion amplification. In general, the vast majority of the study area was determined to have a very low or low susceptibility to ground motion amplification (NEHRP Site classes B and C), though areas exhibiting a thicker sediment layer above bedrock were determined to be moderately susceptible (NEHRP Site Class D). As this research was conducted on a regional scale, site-specific evaluations may need to be undertaken to better assess ground motion amplification.