Experts have raised alarm that a major devastating earthquake is due to hit the U.S. Pacific Northwest, causing massive devastation from Sacramento to Portland, Seattle, and Tacoma, with loss of thousands of lives and displacement of millions.
The doomsday prediction for the region is due to an impending rupture of the Cascadia Subduction Zone, a fault line that extends roughly 700 miles off the coast of the Pacific Northwest from California, through Oregon and Washington, to Vancouver Island in Canada.
Rupture of the subduction zone — a sudden sliding shift or displacement of a tectonic plate beneath another due to accumulated stress — could cause the worst natural disaster in the history of the North American continent, affecting an area of about 140,000 square miles from Tacoma, Seattle, and Portland to Sacramento, a region home to about seven million people.
According to Kathryn Schulz, writing in the New Yorker, FEMA estimates that major earthquakes occur over the Cascadia Fault on the average about once every 240 years. The last major quake occurred in 1700, about 300 years ago, so, in theory, the next major earthquake is overdue.
Seismologists estimate that the impending earthquake could have a magnitude of up to 9.2 and last about four minutes, triggering a gigantic tsunami that reaches the coast about 15 minutes later.
Experts point to the irony of the fact that while most Americans are familiar with the name of California’s San Andreas Fault — the subject of anxious expectations of “the big one” for decades — fewer have heard of the Cascadia Fault, which lies to the north and, in fact, poses greater threat.
According to Schulz, the estimated upper limit of the San Andreas Fault with regard to the power of earthquake it can unleash is magnitude 8.2, compared with Cascadia which can unleash, in the event of a full-margin rupture, an earthquake of magnitude 9.2.
The power of the earthquake depends on whether a part of the subduction zone gives way or the entire zone slips in what is termed a full-margin rupture. In the event of a partial rupture, we could have a quake of magnitude 8.0-8.6, but in the event of full-margin rupture, we could have a quake of magnitude 8.7-9.2.
A full-margin rupture, according to seismologists, would trigger a devastating 700-mile-wide tsunami wall along the Pacific Northwest coast. According to Kenneth Murphy, who heads FEMA’s Region X, covering Oregon, Washington, Idaho, and Alaska, by the time the tsunami recedes, “everything west of Interstate 5? along the Northwest coast “will be toast.”
FEMA projections, based on a planning scenario of the earthquake striking at 9:41 a.m., February 6, when beaches are not yet full, estimates that about 13,000 people could be killed and about 27,000 more injured. The disaster could displace up to one million people and leave two-and-half-million people in need of emergency supplies of food and water.