Long-distance induced tremor observed off western Canada



Using seismic observations made near the Queen Charlotte Margin (QCM), a seismically active region off the western coast of Canada, Aiken et al. add to the growing body of research on how large earthquakes can cause tectonic plates to slip half way around the world. Reaching north from the intersection of the Juan de Fuca ridge, the Cascadia subduction zone, and the Queen Charlotte Fault, QCM underlies the islands of Haida Gwaii and was the site of a magnitude 7.7 earthquake in October 2012. Drawing on seismic readings collected from 1990 to 2012 and using a database of major worldwide earthquakes, the authors identified three earthquakes that induced tremors in QCM: the 2002 magnitude 7.9 Denali earthquake, the 2004 magnitude 9.2 Sumatra quake, and the 2011 magnitude 9.1 Tohoku earthquake. The authors observed the induction not of conventional earthquakes but of deep tectonic tremors, slips of tectonic plates with epicenters located far beneath the surface.