ABSTRACT

The Beaufort Sea seismic cluster in the western Canadian Arctic is an active seismic zone characterized by approximately one magnitude 4 intraplate earthquake per year. Determining the tectonic source of seismicity requires accurate hypocenter information, which is severely hampered by the scarcity of the regional and global seismograph networks in this area. We determine the focal depth of earthquakes with magnitude 4 that occurred in the Beaufort Sea cluster since 1995 by analyzing the teleseismic P‐wave coda containing a visible depth phase (pP and/or sP) observed at stations of the Global Seismic Network. Instead of identifying and picking the direct and depth phases, we calculate the envelope of the autocorrelation of vertical‐component seismograms and stack them along either pP‐P or sP‐P delay time curves. Our results indicate that all moderate‐size earthquakes have a focal depth between 18 and 40 km, with an uncertainty of 0.1–5 km. These depths likely correspond to the base of the crust and possibly subcrustal and favor a model of reactivation on high‐dip fossil normal faults due to sediment loading at the Mackenzie delta. These deep earthquakes may potentially trigger submarine slope failure on the continental slope or shelf and could represent a source of hazard for the coastal communities.

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