The 1933 Ms = 7.3 Baffin Bay earthquake: Strike-slip faulting along the northeastern Canadian passive margin

Abstract

The 1933 November 20 (Ms = 7.3) Baffin Bay earthquake is one of the largest instrumentally recorded passive margin earthquakes. Analysis of seismograms of this earthquake shows strong evidence for strike-slip faulting, which contrasts with the generally accepted belief that Baffin Bay is dominated by thrust faulting. The best-fitting solution consists of a large strike-slip subevent (strike 172°, dip 82°, rake 6°) followed by two smaller oblique-thrust subevents (strike 190°, dip 30°, rake 62°). All subevents occur at a depth of about 10 km. An instrumental moment magnitude of 7.4 was determined. Preliminary analysis of subsequent large (magnitude ≥6.0) earthquakes in Baffin Bay finds additional evidence for strike-slip faulting in the region. The results for Baffin Bay, together with those for other passive margin earthquakes, suggest strike-slip faulting may be more prevalent in these regions than was previously believed.