Abstract

We collected site‐specific geophysical data at 28 seismic stations on various soils in Alberta, Canada. Noninvasive seismic procedures are combined with the earthquake database and other available regional data sets to improve current understanding of earthquake site effects at the stations. Such an understanding allows the separation of site effects from source and path effects, which is important for ground‐motion modeling. Dispersion data sets were compiled using multichannel analysis of surface waves and ambient vibration array field methods. We also computed microtremor horizontal‐to‐vertical spectral ratios using three‐component single‐station measurements. Independent and joint inversion of these two data sets allowed us to characterize 18 seismic stations in terms of shear‐wave velocity–depth profiles.

We report the range in the time‐weighted average shear‐wave velocity in the upper 30 m (VS30) derived from average shear‐wave velocity–depth profiles for each site and their corresponding National Building Code of Canada (NBCC) site classification. Corresponding time‐averaged velocity values are also computed for the top 5, 10, and 15 m. The parameter that is best constrained is VS15, which is related to relatively thin (<30  m) sedimentary overburden in Alberta. In general, Alberta seismic stations are typically characterized by regolith <30  m thick with low shear‐wave velocity (200  m/s), underlain by material with a higher shear‐wave velocity (>400  m/s). NBCC site classes are limited to C and D for the sites we surveyed, with D being the predominant site class.

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