Earthquakes not related, says seismologist

  • Apr. 28, 2014 3:00 p.m.

By Jane Wilson–A magnitude 4.2 earthquake hit south of Queen Charlotte last Thursday (Apr. 23), while a 6.6 shook northern Vancouver Island the previous day. The events were unlikely to be related however, according to Dr. John Cassidy, seismologist with Natural Resources Canada. “We don’t think so,” he said, “We’re quite a young science, but they’re very different fault systems.”The Vancouver Island earthquake was a horizontal slipping in the Nootka Fault Zone, which is not one fault, but a broad zone of seismic activity, said Dr. Cassidy. The 2012 Haida Gwaii earthquake was a subduction event in a new fault dipping towards the islands.The 4.2 on Thursday was likely an aftershock from the 2012 earthquake, said Dr. Cassidy. There are still almost daily aftershocks being recorded but most are not felt as they as are smaller than magnitude 3. Thursday’s earthquake was felt by quite a few people in Port Clements, Tlell and Queen Charlotte, he said, because it was a little closer than the other earthquakes, just along the coastline south of QC.The small earthquakes do not reduce the chances of another large earthquake, as they do not release enough energy, said Dr. Cassidy. “Along the coast of BC we can expect a big one at any time.”There is more of a chance of a large earthquake on Moresby Island than on Graham Island because the 1949 earthquake off Graham Island was large enough to have released a significant amount of energy, he said. That earthquake was a magnitude 8.1 and was Canada’s largest recorded earthquake.Dr. Cassidy encourages residents to report earthquakes they feel to the Natural Resources website as it provides valuable information to the researchers. The site can be found at www.earthquakescanada.nrcan.gc.ca/dyfi-lavr/known-connu-eng.php, or by searching “Earthquakes Canada Did you feel it?”More information about recent earthquakes can be found at the Earthquakes Canada site and real time alerts can be found on twitter by following “CanadaQuakes.”

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