6th earthquake in 36 hours hits B.C., measuring magnitude 4.3

Dec 19 2017, 9:17 pm

The U.S. Geological Survey has detected another seismic event near the cluster zone of earthquakes that began Saturday afternoon.

The undersea earthquake on Sunday at 10:51 p.m. had a magnitude of 4.3 and its epicentre was located just kilometres from five other earthquakes that happened on Saturday and early Sunday morning.

The site of the cluster zone is about 186 kilometres southwest of Bella Bella, northwest of Vancouver Island, and where the Juan de Fuca plate begins to meet the North American tectonic plate. The latest event had a shallow depth of 13.6 kilometres.

The last five earthquakes are believed to be aftershocks to the first earthquake on Saturday at 2:54 p.m. measuring magnitude 4.3. This led to a series of other earthquakes in the area, beginning with the magnitude 5.1 event later that evening at 6:57 p.m.

Three more earthquakes at magnitudes of 4.0, 4.5 and 4.9 hit the same area in the early morning hours of Sunday between 1:40 a.m. to 2:45 a.m.

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 fact, smaller earthquakes could 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.

Red indicates the latest earthquake; orange indicates the three earthquakes that occurred on Sunday morning.
december 21 2014 earthquake 2
Image: U.S. Geological Survey


Feature Image: Earthquake seismograph via Shutterstock

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