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The West Coast “Big One”

The West Coast “Big One”
 

If you have lived anywhere in California, you have heard about the “Big One” coming sometime in the next 20-30 years.  It doesn’t matter whether you live in San Francisco, San Bernadino, Los Angeles or San Diego, the possibility of a destructive earthquake is very real.  Most folks are not aware of the many smaller faults located in the state, however just about everyone in California and across the United States knows about the San Andreas Fault.  Running almost the entire length of California, it is one of the most studied and widely understood faults both in the United States and around the world.

Scientists know that every fault line has a limit on the amount of stress that can build up before that stress is forced to release.  Much research, based on the size of the fault, has been done to determine how far it will slip when it reaches the maximum stress level.  From the information gained with multiple research studies, scientists have concluded that the next “Big One” along the San Andreas Fault will be very powerful – probably close to 8.2 on the Richter scale.

We know that the 1989 earthquake in Loma Prieta was a 6.9 magnitude temblor that killed 63 people and triggered damages that totaled more than six billion dollars. An 8.2 earthquake has the potential to cause even more destruction and loss of life.  Of course, California residents should be prepared for a powerful quake in the near future, but did you know that there is another fault line located to the north of the San Andreas Fault?  It is called the Cascadian Subduction Zone and it actually starts near Cape Mendocino in California and runs north along the coast, stopping close to Vancouver Island in Canada.  It is called a subduction zone because it is where one tectonic plate (the Juan de Fuca plate) is slipping under another one (the North American plate).

Our planet has number of tectonic plates; they are gigantic pieces of the earth’s crust and mantle that drift along very slowly over time.  Very slowly, oceans and continents are rearranged, as these plates slide, undetected, alongside of each other.  In some places, one plate will begin to slide under the other plate and eventually it gets wedged tight and can no longer move.  As the North American plate gets stuck on top of the Juan de Fuca plate, pressure is building up causing the “stuck” edge of the North American plate to bulge and compress.  The increasing pressure cannot be maintained indefinitely and eventually it must be released.  When that happens, all or part of the subduction zone will give away and drop, causing a quake that will be much more powerful than anything that will happen along the San Andreas Fault line.

Seismologists are predicting that if only part of the subduction zone gives way, it will cause a powerful earthquake that has a magnitude between 8.0 and 8.6.  It will certainly be a “Big One”.  However, if the whole subduction zone gives way in one drop, called a full-margin rupture, it will cause an earthquake that registers anywhere from 8.7 and 9.2 – a “Mega-Quake”!  Over the course of the past ten thousand years, researchers have determined that there have been 41 mega-quakes in the Cascadian subduction zone, or about one every 243 years.  The last mega-quake was actually 315 years ago and since then, we have built cities and towns on top of the worst fault line on our continent.

A subduction-zone quake is different than other seismic activity.  When the ground gives way, disaster upon disaster will occur. When the violent shaking begins, the electrical grid will begin to fail in the area and beyond.  Homes that are not bolted down will begin to collapse.  Commercial properties built before 1994 will also begin to collapse if they have not been retrofitted.  It has been estimated that 75% of the commercial buildings just in Oregon were not designed to hold-up when the Cascadian mega-quake occurs; therefore, it is imperative that commercial property owners strengthen their buildings before it is too late.

Soon after the tremors stop, an even more destructive natural disaster will occur along the coastline.  The Northwest coastline from Canada to California and the Cascades to the continental shelf underneath the ocean will give way, dropping close to six feet.  As that happens, the same area will rebound up to 100 feet in a westward direction.  In a matter of minutes, the area will lose the elevation increases gained over many centuries.  The continental shelf beneath the Pacific Ocean will also experience a major shift, causing the displacement of an unimaginable amount of ocean water.  The shifting will cause the water to swell upwards before collapsing, sending a wall of water (possibly 700 miles long) crashing to the coastline soon after the earth stops moving.  The combination of such a powerful mega-quake and the subsequent tsunami will ensure that this catastrophe goes on record as the worst natural disaster in this continent’s history.

Because areas miles away from the Cascadian subduction zone will feel the rippling effects of this mega-quake, commercial property owners from southern California to Washington State and Vancouver Island must understand that the now is the time to strengthen their buildings, making them as safe as possible before this disaster happens.  Saunders Commercial Seismic Retrofit has experienced teams on the West Coast and they work with commercial building owners, providing a comprehensive inspection and a cost estimate for the maintenance needed to strengthen their property.  Each building is different and the professionals at Saunders Commercial Seismic Retrofit will customize the retrofitting process to meet current building codes.  In addition, they will work with the property management team to ensure potential business disruptions are minimal.  Call today to schedule an appointment!

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(949) 646-0034

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