Magnitude 4.2 earthquake detected off Vancouver Island coast

Dec 19 2017, 9:25 pm

A magnitude 4.2 earthquake has been detected off the coast of Vancouver Island on Saturday evening.

According to the U.S. Geological Survey, the undersea tremor at 5:49 p.m. had an epicentre 200 kilometres west of Port Hardy and a shallow depth of 10 kilometres. No damage is expected given the location and magnitude of the earthquake.

The area has been a seismic hotspot over the past month. A swarm of seven magnitude 4.0 to 5.1 earthquakes hit the area from December 20 to 22 and a magnitude 5.2 event also occurred yesterday morning.

january 3 2015 bc earthquake
Image: USGS

All of these earthquakes were within the small northern area between Haida Gwaii and Vancouver Island – where the Juan de Fuca plate is pushed underneath the North American Plate by the Pacific Plate.

A seismologist recently told Global News that there has been more seismic activity in the area since the Haida Gwaii earthquake of October 2012.

Thousands of earthquakes hit B.C. each year, but only a small fraction of the events measure a magnitude of 3 or greater.

Do small earthquakes really delay big earthquakes?

While it is generally believed that smaller earthquakes may delay the “Big One” by relieving pressure along the fault lines, seismologists say this is incorrect. Smaller seismic events do relieve some pressure, however, it requires many small earthquakes to release the same energy given off by one significant earthquake. For instance, an earthquake releases 10 times more energy for every one point increase on the richter magnitude scale.

In some cases, smaller earthquakes precipitate larger earthquakes, such as the magnitude 7.3 seismic event that hit the coast of Japan on March 9, 2011. Two days later on March 11, the powerful magnitude 9.0 earthquake occurred and caused a devastating tsunami that reached far inland. In the weeks and months after the main event, Japan detected more than 900 aftershocks.

Earthquakes can also be a sign of possible volcanic activity. In October 2007, a cluster of small earthquakes near B.C.’s potentially active Nazco Cone, about 75 kilometres west of Quesnel, led the Geological Survey of Canada to believe that magma was moving underground within the area – a possible sign of a pending volcanic eruption.

Feature Image: Earthquake seismograph via Shutterstock

DH Vancouver StaffDH Vancouver Staff

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