Seismicity and seismic monitoring of Canada’s volcanic zones

Abstract

Canada’s recently active volcanic zones (e.g., eruptions during the past 10,000 years) are all located along the tectonic plate boundary region of western Canada, extending for more than 2000 km from southern British Columbia to the Yukon/Alaska border. In this article, we describe the history of seismic monitoring in and near these volcanic zones and the past and current seismicity detection thresholds. The most recently active volcanoes in Canada are Tseax Cone (~1700) and Lava Forks (1800’s), both in northwestern British Columbia. However, no eruptions have occurred in Canada since the deployment of the earliest seismographs in 1898 (Victoria, BC) and 1904 (Sitka, Alaska). Seismic detection levels have decreased from M~7 in 1900 to M~0-1 (in many regions) today, with more than 120 seismic stations currently operating in British Columbia and the Yukon, including ~20 seismic stations within the volcanic zones. The most recent significant seismic activity attributed to volcanic zones in Canada is the 2007 Nazko Cone earthquake swarm when nearly 1000 tiny (M<3) earthquakes occurred here over the span of about two months. These were all deep earthquakes (~30 km) near the base of the crust and showed the patterns expected from an injection of magma deep into the crust. Prior to that, at the western end of the Anahim Volcanic Belt, more than 40 felt earthquakes occurred from 1940-1943. We provide a summary of these two swarms and other seismicity as well as some recent and ongoing studies into seismicity at some of Canada’s volcanic zones and new developments in seismic monitoring of volcanoes (including using distributed acoustic sensing).