Focal Mechanisms for Eastern Canadian Earthquakes, 1994-2000

Abstract

First motions from sixty earthquakes, mostly of magnitude 4.0 or greater, occurring in eastern Canada from 1994 through the end of 2000 were analyzed in an effort to determine their focal mechanisms. Focal mechanism solutions were obtained for thirty-seven. The seismograph station distribution in Canada is not uniform, and the percentage of events for which focal mechanisms could be determined is directly related to station density and azimuthal coverage. Well constrained solutions could almost always be determined for earthquakes occurring in the populated regions of southeastern Canada, where the network density is relatively high. We had moderate success in regions, such as the central Arctic and Labrador Sea, where station density is low but azimuthal coverage is adequate to good. Few focal mechanisms could be determined for the extreme northeast and southeast offshore regions, where both density and azimuthal coverage are poor. In this paper we summarize the focal mechanism...