- Local Magnitude Formula for Western Alberta | Presentation/Poster
We examine the distance attenuation of peak Wood-Anderson (WA) amplitudes obtained from earthquakes in western Alberta, to develop a regionally-calibrated local magnitude (ML) equation. A comparison of WA amplitudes from earthquakes and mining/quarry blasts in the region show that both event types decay at similar rates with distance and demonstrate a considerable Moho-bounce effect between 100 km and 220 km. Motivated by this observation, we merge the two amplitude datasets, and model the regional attenuation using a trilinear model to account for the observed shape of attenuation. We also determine a site correction for each station, which enables determination of ML for a reference site condition. The derived ML equation results in unbiased magnitude estimates with distance in western Alberta, and attains systematically lower values than the existing magnitudes computed based on standard ML models.