At 10:13 PM eastern US time, a magnitude 5.7 earthquake struck the Cascadia Subduction Zone in the Pacific, just off the coast of Vancouver, BC, CANADA. This is the FIFTH earthquake there today and the second at Magnitude 5 or greater.
Like the four earlier quakes, this one took place at a very shallow depth of about ten kilometers. This is a serious development.
The Cascadia Subduction Zone (CSZ) which runs from Vancouver down along the Washington and Oregon coastlines is the single most dangerous earthquake fault region - far more dangerous than the San Andreas Fault in California.
The CSZ is where the Pacific Tectonic Plate goes beneath (Subducts) the North American Plate. The Pacific Plate pushes north/northwest while the North American Plate pushes south.
Over millions of years, part of the North American Plate got "snagged" by the Pacific Plate, and this "snag" has the effect of pushing the North American plate - which then created the Cascadia Mountain Range and, to a lesser extent, the Rocky Mountains.
Seismologists say that when the North American Plate becomes "un-snagged" that will be "the big one" for the West Coast. All the stress built-up over millions of years, could be released in one fell swoop, thus flattening out the Cascadia mountain range, as the newly-freed North America Plate returns to its pre-snagged state, moving to the west by upwards of 100 miles!
Of course, there is no way to accurately predict earthquakes, and no one is claiming that "the big one" is anywhere close to taking place. But whenever a Magnitude 5 or above strikes in that area, it is of great concern. Smaller earthquakes can sometimes loosen-up the ground and permit much larger earthquakes.
The 5.7 is the strongest earthquake to strike that area today.
Folks on the west coast are urged to be vigilant. You should have emergency food, water, heating capability if electric goes off, and, of course, flashlights and portable radios with spare batteries to prepare for an emergency.
Readers can look at the U.S. Geological Survey Web Site to examine the quake data HERE