Story by Andrew Lake
You’re driving down State Street in the early afternoon. Your car starts to shake a little and you think you’ve just hit a rough patch of road. Then you notice that all of the light poles are swaying in sync. Suddenly, you feel your car lurch violently to the side, and you realize you’re in an earthquake. Or maybe the earthquake strikes while you’re sitting at a desk at school or work, or at two in the morning when you’re asleep. Do you know what you’d do in any of these situations? Do you have a plan for the aftermath?
“Bend over, grab your knees, and kiss your ass goodbye.” That’s Vincent Garcia’s plan. However, he has also wisely prepared for a major event with long distance walkie-talkies for himself and his family and a backyard shed with a month’s worth of food and water for himself and his partner.
If you’re not as prepared as him, you certainly aren’t alone. You might be like Leslie who knows about the Wasatch Fault, but hasn’t done anything to actively prepare. Or you might be like Ken and Socheata who recently moved here from California and weren’t previously aware of the existence of the Wasatch Fault.
The Wasatch Fault
The Wasatch Fault is really a system of five faults which are, from north to south, the Brigham City Fault, the Weber Fault, the Salt Lake City Fault, the Provo Fault, and the Nephi Fault.
The system is capable of producing a magnitude 7.0-7.5 earthquake around every 270 years, and each individual fault is responsible for that earthquake approximately every 1,300 years.
The average number of years between major earthquakes on the Wasatch Fault System
The number of years since the last major earthquake on the Wasatch Fault System
The number of years since a major earthquake on the Salt Lake City segment.
The number of years since a major earthquake on the Brigham City segment.
The most recent major earthquake was on the Nephi Fault, about 280 years ago, while the Brigham City Fault has gone about 2,420 years without causing a major earthquake. So it stands to reason that the Wasatch Fault System is somewhat overdue for its next large rupture, and the Brigham City Fault is the most likely location for it to occur.
It is worth noting that the Salt Lake City Fault has gone about 1,330 years without a major earthquake, so it is also overdue for a major event.
The Primary Danger
Mere ground shaking is not the only effect of an earthquake, nor is it the most dangerous. According to the University of Utah’s Professor David Dinter, who earned his PhD in Structural Geology from the Massachusetts Institute of Technology, the primary danger from a major earthquake on the Wasatch Fault will be liquefaction. This is when saturated soil behaves like a liquid while being shaken, allowing anything above it to sink into the ground.
According to Dinter, “From about 700 East all the way through downtown, out through the west valley and the encompassing airport, the entire I-15 corridor and much of the intersecting I-80 corridor… are underlaid by liquefiable deposits at depth.” This means the ground beneath these important structures will become unstable and likely cause catastrophic failure of their foundations and, therefore, the structures themselves. Even during smaller earthquakes, liquefaction can still pose a threat.
The Strength of Shaking
Liquefaction aside, just how strong is the shaking caused by a magnitude 7.5 earthquake like we can expect from the Wasatch Fault?
On November 25, 2016 there was a magnitude 3.2 earthquake near Bluffdale that, according to Fox13 News, caused no damage but that approximately 500 people reported feeling. Based on comments left on news articles about that earthquake, it seems many people are using it as a gauge of how dangerous even larger earthquakes might be.
How many times larger the shaking from a magnitude 7.5 earthquake is than a magnitude 3.2 earthquake.
How many times more energy is released by a magnitude 7.5 earthquake is than a magnitude 3.2 earthquake.
However, because the Richter Scale of earthquake intensity is logarithmic (meaning that a single point increase corresponds to a tenfold multiplication of strength), the shaking caused by a magnitude 7.5 earthquake is nearly 20,000 times larger and releases more than 2.8 million times the amount of energy a magnitude 3.2 does. So it is incorrect to assume that the two earthquakes are comparable in their danger. The recent, small earthquake is not representative of the impact a larger earthquake will have.
Before the Earthquake
One of the most important things Utah residents should do to prepare is to begin accumulating nonperishable food and water supplies. You should also attach your home’s water heater to the wall. Doing so will keep it from falling over and spilling during an earthquake which provides you and your family with an additional 50 gallons of valuable, potable water.
Before building up your long-term food and water supply, you should at least prepare a 72-hour kit for yourself and all those with whom you live. The kit should at the very least include food and water, a flashlight and extra batteries, and a first aid kit. Additional supplies you might want include a blanket and extra clothes, cash, prescription medicines, food for pets, and a battery powered radio. Your kit should be kept somewhere that you are sure to be able to access after a major event, such as in your car rather than in your basement.
During the Earthquake
During the earthquake itself, the website of The Great Utah Shakeout advises everyone to “Drop, Cover, and Hold On!” Though it used to be taught that doorways are safe and sturdy, or that you are safest right next to an object in the so-called “Triangle of Life,” it has more recently been determined that it’s best to immediately drop to the ground before the shaking can throw you down, climb underneath a nearby, sturdy object such as a table, and hold onto that object with one arm while covering your head with your other.
After the Earthquake
Even once the earthquake has stopped, there will be smaller aftershocks in the hours and days following. It’s like “that closet where you stuff everything,” Dinter explains. “You open the door, you get the initial shock when everything falls out, and then things fall off the edge of the pile.” Because of this you should get outside if you’re in a building and get to an area away from trees, power lines, and anything else that might fall in the subsequent aftershock.
So what’s the single most important and simplest thing you can do today to begin preparing for a major earthquake? “Designate a meeting place [for your family immediately after the earthquake occurs] so that you can know who is present or who might be injured or buried in the minutes after an earthquake. And then second most important is to, for goodness’ sake, take first aid and CPR lessons,” Dinter advises.
Your meeting place should be outside, near your home where it will be easy to reach, but away from anything that might have become unstable and might fall even after the shaking has ended. It’s also a good idea to sleep with shoes and a flashlight next to your bed to help you navigate your home in case an earthquake occurs at night.