Yesterday on the blog The Extinction Protocol (also here on WordPress), Alvin posted on article relating a new study by the geologists at Oregon State University stating that the likelihood of a massive earthquake occuring in the Cascadia Subduction Zone off of the coast of Coos Bay has gone up to 40% over the next fifty years (more on this estimation a little later). The article was very interesting and can be found at http://theextinctionprotocol.wordpress.com/2012/08/02/study-highlights-growing-risk-for-large-magnitude-earthquake-for-nw-pacific-coast/ ; also, if you scroll down through the comments you will find another link posted by a lady named Donna which leads to a 50 minute video of a state seismologist presenting the hazards to the Multnomah County commissioners in Septmeber of 2010. In the OSU report they state that the likely magnitude of this massive quake would be in the 8.7-9.2 range, which would put it on an even footing with the massive quake in Japan last year and the one in Chile in early 2010.
During the course of the study the scientists state that the southern end of the CSZ ruptures more frequently than the northern, which means that the area from Crescent City, California up to Newport, Oregon is at the greatest risk. A quake of this magnitude would devastate many communities and destroy the infrastructure, making relief efforts extremely difficult. Has this report been carried by the local TV news or newspapers? Not yet. Why? Because the authorities don’t want to alarm the public and because the public prefers to turn a blind eye to the danger, just as it does (for the most part) with volcanoes, even though Mt. Saint Helens gave us a pretty noticeable indication of that dannger back in 1980.
Let’s take a quick look at why this threat exists before I start opining excessively. A subduction zone is a geological area where one of the large tectonic plates of solid rock that we live on is riding over the top of another plate; in this case, the vast North American plate is riding over the top of the much smaller Juan de Fuca plate. As the upper plate rides over the top of the lower one friction builds as the rocks hang up on each other, until it reaches the point where the rocks snap under the strain and an earthquake occurs as the manifestation of the shock waves from that snap. The Cascadia Subduction Zone (CSZ) lies about 50-75 miles off of the coasts of Oregon and Washington, and was actually only discovered within the last 25 years or so. The CSZ is why the Cascade Mountains of the Pacific Northwest are one long string of volcanoes, because as the Juan de Fuca plate is pushed ever deeper it begins to melt, and as it does the resulting magma wells up to the surface and forms our beautiful but dangerous volcanoes.
The OSU study has concluded that the southern end of the CSZ has earthquakes more frequently than the northern, and so they issued their warning that a quake measuring roughly 9.0 has a 40% chance of occuring there over the next fifty years. Now here is where I start taking issue with these “probabilities”. The geologists who study earthquake zones for a living know that quakes are likely to happen in certain areas, but they always couch their predictions in terms of percentages over a half-century or more for two reasons: first, the government doesn’t want to start a panic or mass-migration out of the endangered area, and secondly, the seismologists don’t want to be more specific in their predictions because if they are wrong then they will lose professional credibility and possibly funding.
So let’s look at the historical facts. The CSZ produces massive quakes in the 8.0-9.0+ range about once every 245 years, and the seismologists have verified that through the geologic record (massive quakes leave a lot of signs of their passage if you know what to look for). The last massive quake occured in early 1700 when a 600 mile stretch of the CSZ ruptured, and this quake is still remembered among the Native Americans living in western Oregon. This means that based on the average provided above, the CSZ is roughly 65 years overdue for a massive quake. While 65 years is practically a blink of the eye in geologic time, events that occur at fairly regular intervals don’t like changing their patterns much and therefore tend to stay regular. Personally, I usually double the numbers in a predicted probability, which means we are looking at an 80% probability in the next 25 years, and when a fault is overdue for a major rupture all bets are off.
A magnitude 9.0 quake along the central Oregon coast will shake the entire western half of Oregon for up to five minutes, and shake it hard. This means that bridges will collapse, roads will become impassable from either buckling or landslides, the electricity and communications systems will go down, and many older buildings built of brick and mortar will collapse. Highways 101 and I5 will most likely be unusable except in some locations; it is believed that Highway 101 will virtually cease to exist. And as an added bonus, the quake would generate a tsunami on a scale similar to the one in Japan, which would wipe all of those low-lying towns and developments right off of the map. Watch some of the Japanese tsunami videos on Youtube to get an idea of what to expect.
So are we prepared here in the Northwest? No. As I said above, most people here would rather ignore the threat than take even the most rudimentary precautions. While our building codes in Oregon have slowly begun to require that new constructions have at least some earthquake-resistant features, most of this state was built before the CSZ was even discovered. There are emergency planners and first responders who are taking the threat seriously, but any meaningful improvements that could be made can’t simply because there is no money available to make them. And then there is public complacency to deal with, and I frankly think that the public will fatalistically keep looking the other way until the ground begins to shake.
And it will shake, and sooner rather than later. I constantly monitor the USGS earthquake and volcano hazards maps (available at http://www.usgs.gov) and there have been spurts of activity along the whole Cascadia Subduction Zone in recent months. Just in the past few days there were a half-dozen small to moderate quakes all in the same spot about twenty miles off of the coast of southern Oregon, roughly between Brookings and Gold Beach and right in the danger zone.
I want you to know that I am not being an alarmist, but the danger is very real. All I ask of my friends from Northern California to Washington State is that you look at these links and become aware of what is literally happening under our feet. Even just a few basic precautions like storing fresh water and coming up with a family plan of what to do and where to go when Oregon’s Big One hits can make a world of difference. And if you live in a low-lying area along the coast, as soon as the quake hits head for high ground, for the tsunami would arrive only about 20-30 minutes after the shaking stops – or even less.
And don’t try to surf the tsunami, surfer dudes and dudettes – it never ends well.