Powerful earthquake shakes northern California coastline

A magnitude 6.9 earthquake shook the coast of northern California late Sunday night, and was apparently felt up and down the west coast, from southern California to Vancouver Island.

According to the U.S. Geological Survey, the quake struck at just past 10:18 p.m. Sunday night, centred around 77 kilometres due west of Eureka, Calif., and at a depth of around 16 kilometres. Residents in and around Eureka reported the strongest shaking, which would have likely woken anyone sleeping at the time and could have toppled objects and knocked items off shelves. Nearly 4,000 people reported the quake, most from the rest of northern California and in southern Oregon, but it was also reported as far south as San Diego, Calif., and even as far north as Victoria, B.C.

Nearly two dozen aftershocks, including three of at least magnitude 4.4, have followed since. Many more will likely happen as the fault-zone settles down from this powerful release of energy.

Fortunately, no injuries have been reported and the quake apparently caused no serious damages. A statement from the National Tsunami Warning Center said that there was no danger of a tsunami from this earthquake.

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Northern California is prone to quakes, because just off the coast is where three different tectonic plates meet — the North America plate, the Pacific plate and the Juan de Fuca plate, which runs from northern California all the way to Haida Gwaii, northwest of Vancouver Island. Due to this meeting point, the effect that a quake in this area has on the local communities largely depends on exactly where it strikes.

Fortunately, with the location of this quake, it was the Juan de Fuca plate that took the brunt of the shaking. This is the eighth earthquake of this magnitude or greater to shake the area in the past 100 years. Six of those (including this one) struck on the Juan de Fuca plate and any effects felt along the coast were minimal. The other two struck on the North America plate instead, and caused severe shaking throughout the area. The first of those two, in November of 1980, was a magnitude 7.2 earthquake, centred just off the coast, which injured six people and caused roughly $2 million in damages. The second — also magnitude 7.2, but followed by two aftershocks of magnitude 6.5 and 6.7 — hit the area just to the south of Eureka on April 25, 1992. It touched off rockslides and landslides, damaged buildings and injured nearly 100 people. Total damages from the quake and aftershocks exceeded $60 million.

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