Another Day, Another Earthquake

A violent earthquake, measuring 7.7 on the Richter Scale,  jolted British Columbia's north-central coast last night, frightening residents and forcing many to temporarily leave their homes for higher ground ahead of a possible tsunami.

Tsunami warnings were issued for British Columbia's North Coast, the Haida Gwaii islands, parts of the central B.C. coast, the coast of Alaska and as far away as Hawaii.

Early this morning the warnings were downgraded to advisory status, meaning evacuations were no longer necessary, and they were cancelled altogether a few hours later.

Brent Ward, an earth scientist at Simon Fraser University, said the earthquake was the second largest to hit the country since 1949, when another earthquake was recorded in the same area with a magnitude of 8.1.

"It's an earthquake in an area that gets a lot of earthquakes," he said. "It's a tectonically active area."

Ward said the area is known as the Queen Charlotte fault, where the earth's plates slide horizontally across each other in a strike-slip action, similar to what happens along California's San Andreas fault.

"Stresses build up because of that movement, and every so often we get the release of that stress in the form of an earthquake."

Ward said he wasn't surprised the tsunami warning was short-lived because the strike-slip movement along the fault doesn't generally trigger large tsunamis.

"To trigger a tsunami you need to have a vertical movement of the sea floor, and it's that vertical movement that displaces water and triggers the tsunami.

The tsunami did reach Hawaii this morning (actually about 10:30 p.m. Hawaii time) but was pretty small. 

Authorities had earlier ordered at least 100,000 people on the island to move to higher ground.

The Pacific Tsunami Warning Center said the first wave was three-feet high and less forceful than expected. Some forecasts had predicted a wave of up to six-feet high.

"The tsunami arrived about when we expected it should," senior geophysicist Gerard Fryer told reporters at a news conference, adding: "I was expecting it to be a little bigger."