Crustal Shear-Wave Velocity Models Retrieved from Rayleigh-Wave Dispersion Data in Northern Canada

Abstract

Baffin Island is one of the several seismically active regions in the far north of Canada. In 1933, a strong earthquake with M w 7.3 occurred in the region. On 7 July 2009, a relatively strong earthquake with M w 6.0 occurred in the same area. This earthquake was very well recorded by many modern seismic stations. We systematically organized the Rayleigh‐wave displacement records, measured Rayleigh‐wave dispersion data at 28 stations surrounding the epicenter, and retrieved the S ‐wave velocity models. We used a previous model for the Western Quebec seismic zone as the initial model in our analyses and found that the velocities of all models at the shallow depths (<15 km) were obviously slower than those of the initial model. In the middle crust, the velocities in most models were close to those of the initial model. In the directions of azimuths 171°∼218° and 241°, the velocities in the middle crust were faster than those of the initial model. In the directions of 263°∼279°, the velocities in the middle crust were slower than those of the initial model. The slowest S ‐wave velocities in the top layers occurred in the directions of azimuths 90° and 218°. These findings indicate differences in the existing crustal structures.