Instruments recorded the moment the earthquake struck.

Last night, just after 10 p.m., a 2.5-magnitude tremor hit seven kilometres northwest of Langford, 27 kilometres below the surface.  Seismologist Dr. John Cassidy, from the Pacific Geoscience Centre, said the Juan de Fuca plate pushes against the North American Plate, causing stresses along a fault line.

“It’s the movement of the plates that causes these really tiny earthquakes, but also, typically decades apart, much bigger earthquakes,” Cassidy said.

It’s called strike-slip, the same mechanism that led to the earthquake off the coast of Alaska in January.  That one led to evacuations on Vancouver Island over fears of a tsunami.  But this one was minor.  Despite that, the government’s website received 100 reports from residents in Cobble Hill, Colwood, and as far away as Vancouver.  From Twitter, one writer posted, “Definitely felt it! I thought a car crashed into the house.”

Luckily, no reports of damage and officials don’t expect any, according to Cassidy. “There are, on average, about a thousand small earthquakes around Vancouver Island each and every year.  Only a few of those will be felt.  Maybe a half dozen will be felt.”

Still, experts say input from the public goes a long way in helping scientists develop an updated hazard model.  Social media also helps connect experts around the world who can quickly analyze results. The data will be used to make buildings safer and plan a better disaster response.   Cassidy said it all helps.

“It’s information that is used by emergency managers for developing earthquake scenarios and for planning response to future earthquakes. What can you expect and where can resources be deployed most effectively,” Cassidy said.

Scientists say this won’t be the last earthquake, but with each one, they gather more information that could one day help save lives.

Mary Griffin