Five earthquakes, including a magnitude-6.0, struck west of northern Vancouver Island Monday. According to Natural Resources Canada, the first quake hit at 8:44 a.m. at a magnitude 5.1. The second was a 5.6 at 11:13 a.m. The third was at 11:49 a.m. and was a 5.8. The fourth and largest was a 6.0 magnitude at 12:56 p.m. And the fifth was at 4.8 magnitude at 3:38 p.m. (all times in PST) None of the quakes caused a tsunami warning. Andrew Schaeffer, a seismologist with Earthquakes Canada, said during the first four earthquakes, two plates were sliding past each other, which don’t generate a tsunami.
“To generate a tsunami, you need to have some vertical movement on the fault and this is not what happened,” Schaeffer said. “It’s pretty common to get these events in this area… it’s a strike-slip fault between North America and the Pacific,” Schaeffer said. “Magnitude 5s and larger [are common]. The largest we see in the area is about a 6.0.”
Each earthquake was around 170 kilometres west of Port Hardy, at a depth of five-kilometres. “This is where a few plates come together that accommodate the relative motion between the Pacific Ocean and the North American Plate. This area is a little bit separate from the Cascadia Subduction Zone,” Schaeffer said.
“It’s one of the more seismically active areas, for example, over the last year there’s been almost 90 magnitude three earthquakes within 100 kilometres of this region. Almost 20 magnitude fours.”
Schaeffer says the quakes coming in a sequence is often seen, although it’s not as common for the magnitudes to climb like they did on Monday. However, it has happened before.
Seismologist John Cassidy says there are also numerous aftershocks in the area. He also said there was a 6.3 magnitude earthquake and a 5.5 magnitude earthquake in July, 60 to 80 kilometres to the northwest of Monday’s four earthquakes.
— John Cassidy (@earthquakeguy) December 23, 2019
While the region northwest of Vancouver Island’s northern end experiences frequent seismic activity, it has been particularly active today.
A series of four offshore earthquakes took place this morning, ranging from 5.1- and increasing in intensity to two 6.0-magnitude quakes.
According to Earthquakes Canada, it struck at a depth of five kilometres (three miles) and the epicentre was located 168 kilometres (104 miles) west of Port Hardy, 336 kilometres (209 miles) west of Campbell River, and 508 kilometres (316 miles) northwest of Vancouver.
Like the other quakes, there aren’t any reports of damage and none are expected, and there also isn’t a tsunami threat from this event.