Two-dimensional seismic velocities and structural variations at three British Columbia Hydro and Power Authority (BC Hydro) dam sites, Vancouver Island, British Columbia, Canada

Abstract

Summary In June, 2017, we acquired seismic data along five linear profiles at three British Columbia Hydro and Power Authority (BC Hydro, a Canadian provincial Crown Corporation) dam sites (John Hart, Ladore, and Strathcona Dams) on Vancouver Island, British Columbia, Canada. We also attempted to acquire linear seismic profiles at two additional BC Hydro dam sites (Ruskin Dam and Stave Falls Dam) east of the City of Vancouver, British Columbia, Canada; however, due to a seismograph programming error, little active-source data from Ruskin Dam and Stave Falls Dam were recorded. Thus, results from Ruskin Dam and Stave Falls Dam are not included in this report. At the three dam sites with successful data acquisition, we acquired both active- and passive-source data. Data acquisition details for each of the three dam sites varied in terms of seismic sources, the number of seismographs, and profile length and orientation. However, for active-source acquisition at each dam site, we acquired one or more linear seismic profiles ranging in length from about 150 to 400 meters (m), and along each profile, seismograph spacing was either 3 m or 5 m (see appendix 1). All data were recorded in three components (vertical and two horizontals). To greatly increase the resolution of the seismic velocity structure along these profiles, we co-located active sources at each seismograph.