J352 Feature Article: The Big One

The Big Cascadia Earthquake: What to Expect?


It’s no secret that Northwestern coastline of the U.S. is expecting and quite frankly long overdue for a massive earthquake in the near future. Pacific Northwesterners and scientists have aptly named it “the Big One”. The earthquake is called “a megathrust”, which sounds incredibly ominous, but is otherwise known as a subduction zone earthquake. Daryl Hare, who owns a seismic retrofitting business in the Portland area, discussed the surprising facts surrounding a “megathrust” earthquake. A typical “crustal fall earthquake” is caused by two tectonic plates sitting parallel of each other and also moving against each other in opposite directions, releasing small quakes over time to release pressure. The “Big One” is going to be nothing like that.


The Cascadia plate runs from Vancouver Island in Canada all the way down to the California-Oregon border. Where land meets ocean is where Cascadia comes in contact with a micro-tectonic plate, Juan de Fuca. But Juan de Fuca doesn’t just come in contact with Cascadia, in fact, Juan de Fuca has been sliding underneath his tectonic friend for hundreds of years, causing intense levels of pressure. These levels will continue to increase and eventually—pop. Cascadia will jump 15 feet in the air, taking the entire Pacific Northwest along for the ride.


Since subduction zone earthquakes were so infrequent in the past and considering that the last one was in 1700, scientists didn’t understand them until just a few decades ago. However, here in the Pacific Northwest, we live directly on the Ring of Fire, a horseshoe shape that stretches from the Southeast of Asia to the tip of South America, which is directly related to plate movement and oceanic trenches. Approximately 80 percent of the earth’s earthquakes occur within this region of the Pacific Ocean. Unfortunately, due to the fact that these scientific discoveries were made so recently, many buildings in Oregon are ill-equipped to handle a major earthquake. These buildings are called “unreinforced masonry” and according to Hare, “there are thousands of them in the state of Oregon”. At the turn of the century, building consisted of stone and brick, buildings such as old churches and other historic buildings, and in the event of a massive earthquake, they won’t survive.


Today, laws require building owners or homeowners to bring their properties up to code, but only if they are doing what is considered to be a “major upgrade”. Hare suggests that these laws will tighten as people become more aware of the dangers of unreinforced buildings. Many people are no longer interested in living in beautiful historic buildings due to the danger they may pose. What’s the solution? Seismic retrofitting. While very difficult, it involves drilling through stone and filling it with concrete and epoxy in order to allow flexibility, the process is currently the only solution to maintaining an old building in the event of an earthquake. While there might not be an exact date on the Pacific Northwest’s “Big One” it is always better to be safe than sorry.


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