Two earthquakes on Baffin Island and their tectonic implications

The source parameters of two earthquakes that occurred under Baffin Island, Canada, were determined from surface wave spectrum analysis. By selecting records for which the travel paths were essentially continental, it was possible to determine precisely both the focal mechanism and focal depth. The utilization of the phase spectrum complemented the information obtained from the amplitude spectrum studies. It is proposed that the stress pattern of these very shallow (4–6 km) earthquakes is a dilatational stress acting normal to the general trend of Baffin Island. Short-period surface wave attenuation for less than 20-sec periods was found to be very low under the Canadian Shield.