Magnitude 4.1 earthquake hits B.C. coast, the 7th tremor since Saturday

Dec 19 2017, 9:17 pm

Yet another earthquake has been detected just north of Vancouver Island, the seventh of a swarm of seismic events that began Saturday afternoon.

According to the U.S. Geological Survey, the undersea earthquake occurred at 1:01 p.m. on Monday and had an epicentre about 185 kilometres southwest of Bella Bella – near the fault lines of where the Juan de Fuca plate begins to meet the North American tectonic plate.

It had a deep depth of 20.6 kilometres and was just kilometres away from the epicentres of the six other earthquakes that hit the region over the last two days.

Here is a list of the earthquakes that occurred in the area since Saturday:

  1. Saturday at 2:54 p.m. – magnitude 4.3 (10 km depth)
  2. Saturday at 6:57 p.m. – magnitude 5.1 (10 km depth)
  3. Sunday at 1:40 a.m. – magnitude 4.9 (12.4 km depth)
  4. Sunday at 2:19 a.m. – magnitude 4.0 (22.2 km depth)
  5. Sunday at 2:45 a.m. – magnitude 4.5 (10 km depth)
  6. Sunday at 10:51 p.m. – magnitude 4.3 (13.6 km depth)
  7. Monday at 1:01 p.m. – magnitude 4.1 (20.6 km depth)

The earthquakes that followed the first event on Saturday afternoon are believed to be aftershocks.

No damage was made by any of the events as they were a distance away from population centres.

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 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.

Location of Monday’s magnitude 4.1 earthquake at 1:01 p.m.
december 22 2014 earthquake 2
Image: USGS


Feature Image: Earthquake seismograph via Shutterstock

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