ONE
THE REALLY BIG ONE
Someday a catastrophic, 9.0 mega-earthquake will bring devastation along the more-than-620-mile-long Cascadia subduction zone, which stretches offshore from Mendocino Bay, California, to Vancouver Island, British Columbia. Fifteen million people in the region will have their lives dramatically disrupted. Nearly eight million will experience the collapse of modern infrastructure. The Really Big One might be tomorrow, or it might not happen in our lifetime. With no way of knowing which it will be, the time to get ready is now.
Efforts to increase readiness through improvements to building codes and infrastructure systems around the Northwest are underway, but without painful memories of death and destruction—like those from the catastrophic earthquakes that spurred Japan and Chile to become the most earthquake-ready countries in the world—lack of funding and competing priorities keep progress alarmingly slow.
The shaking will destroy the conveniences of modern life on which we rely: phones and internet will disconnect; power, gas, and water lines will break. Blocked roads and collapsed bridges will prevent travel. Like in the pioneer days, the only people you will be able to look to for help are your neighbors.
But the good news is that you—and they—will likely survive if you live outside the coastal tsunami zone: a defined area along the Pacific Ocean—meaning not in Portland or Seattle—where a quake-triggered tsunami would hit (see this page for further information). The Federal Emergency Management Agency (FEMA) estimates that, in many scenarios, around 99.95 percent of people outside the coastal tsunami zone will likely survive. But surviving the earthquake won’t be the only challenge. Getting through the two weeks you’ll be waiting for outside help to arrive will be another survival challenge.
Part of becoming prepared is understanding the damage a mega-quake will do and just what you’re getting ready for.
UNDERSTANDING THE THREAT
Earthquakes are startlingly common along various types of faults, but only subduction zone faults cause earthquakes that exceed about 8.3 on the Richter scale. A 9.0 earthquake is both rare and almost unimaginably powerful.
All earthquakes measuring 9.0 or above—and about 90 percent of total earthquakes in the world—have taken place along the Ring of Fire, the area of the Pacific Ocean basin from near the southern tip of South America, north through western North America, west past the Aleutian Islands, and south past Japan and through the Philippines to the islands off the east coast of Australia. Named for the volcanic activity along this arc, the Ring of Fire is where coastal plates collide with continental plates. In the last fifty years, every subduction zone fault around the Ring of Fire, except the Cascadia subduction zone, has produced an 8.0 or stronger earthquake.
The North American Plate is beneath much of North America. When the Juan de Fuca Plate slips past it, there will be a massive earthquake.
While residents of other subduction zones experience ground shaking as a normal part of life, people in our region think of it as unusual. From 2010 to 2015, Alaska (which borders the northern Aleutian Trench subduction zone) had 9,020 earthquakes of magnitude 3.0 or above, averaging 1,804 a year. In that same period, Oregon had only 17 similar earthquakes, averaging 3.5 a year, and Washington had 60, averaging 5 a year.
The Cascadia subduction zone has produced 40 earthquakes measuring 7.5 magnitude or higher in the last 10,000 years. Thirty-eight of those were 8.0 or stronger and 4 were 9.0 or above. This means major Cascadia earthquakes occur, on average, every 246 years. Not all Cascadia earthquakes, even the big ones, have been full-rip, which unlocks the entire fault line; many have involved breaks in only one area of the fault. The last major Cascadia earthquake, an estimated full-rip 9.0, occurred on January 26, 1700—more than 300 years ago.
About 70 to 100 miles off the West Coast of North America, two tectonic plates inch toward each other at approximately the speed your fingernails grow. Pressure builds up as the coastal Juan de Fuca and North American Plates collide and “lock,” blocking the coastal plate from moving further under the North American Plate. The stress has been building for hundreds of years. In a full-rip event, the whole zone will unlock—all 620 miles—from Mendocino Bay, California, to Vancouver Island, British Columbia, causing a massive release of pent-up energy in the form of a subduction zone earthquake.
Also called “megathrusts,” these are the largest earthquakes, as they push one of the plates up relative to the other, causing a lot of shaking at ground level, often for relatively long periods of time: multiple minutes. After the earthquake, the displacement of the plates under the ocean causes a wall of water to reach the coastal region. In many places, this tsunami takes only fifteen minutes to arrive; in others, up to two hours.
Such a tsunami won’t reach Seattle, though, and most people will survive the event. Speculation that the Really Big One will make the region largely uninhabitable ignores the fact that other countries have experienced catastrophic earthquakes. Since 1950, there have been 9.0 or above earthquakes in Chile, Alaska, Japan, Indonesia, and Russia. In all cases, populated areas have been rebuilt, often with stronger building codes to make the location more resilient. The only question is whether the Pacific Northwest will increase its resilience as a result of what we know now or only as a reaction to the losses that will come after a mega-earthquake here.
MAGNITUDE MATTERS
The difference between an earthquake of magnitude 8.0 and a 9.0 one is—literally—exponential. The magnitude of an earthquake measures the amount of energy it releases, but just what a single point on an exponential scale means can be hard to fathom.
Legend tells of how the man who invented chess was to be rewarded by the emperor of India for his accomplishment—he could ask for anything as his reward. But his request was deceptively simple: he asked that he be granted one grain of rice on the first square of the chessboard, two grains on the second square, and double the number of grains on each of the next sixty-two squares.
Take some rice and a chessboard and see how far you can get on figuring out his reward. The last square of the chessboard would have to accommodate eighteen quintillion grains of rice, or about 210 billion tons.
That is how the Richter scale, measuring earthquake magnitude, works. It is also why it is so hard to imagine that an 8.0 or 9.0 Cascadia earthquake will be nothing at all like the 6.0 earthquake we may have already lived through—especially since most California earthquakes have lasted fifteen to thirty seconds, but the Really Big One will last four to six minutes.
INTENSITY MATTERS TOO
Intensity measures the severity of shaking and damage from an earthquake. It describes what people in the earthquake experience, as well as what it does to buildings and infrastructure. Intensity I events are described as “not felt/no damage”; Intensity X earthquakes inflict “extreme shaking and structures destroyed.”
Here lies one of the few pieces of good news about the Cascadia earthquake: the subduction zone lies offshore, far from the cities and rural areas the earthquake will impact. This means the intensity we will feel will be less severe than if a seismic fault directly beneath our neighborhood ruptured and caused an earthquake. This is why even though the San Andreas Fault can’t exceed 8.3 magnitude earthquakes, its location so close to millions of residents makes it such a concern—the intensity of the shaking and damage will be high.
Oregon, Washington, and Idaho all have faults outside the Cascadia subduction zone that can produce destructive earthquakes. Damage from earthquakes on these faults could be considerable despite their smaller magnitude. While help would quickly rush in from nearby areas in a localized earthquake, a full-rip 9.0 Cascadia event means it will take two weeks for help to arrive since the entire region will be impacted. Thankfully, the same supplies you gather to prep for the Really Big One will help you in the event of a smaller earthquake.
AFTERSHOCKS
Unlike a hurricane or tornado, which passes through a region, what we consider an earthquake is usually just the beginning of a sequence of aftershocks that can last for years. While most aftershocks are so small that only seismic instruments can sense them, numerous aftershocks from the Cascadia earthquake will be strong enough for people to feel, and they could cause more damage to weakened structures, rack frayed nerves of survivors, and complicate response and recovery efforts. Here’s how aftershocks generally work:
The largest aftershocks are usually about one magnitude less than that of the main shock.
The day of the main shock will have the most aftershocks.
The following day will likely have about half as many, the next a third, the fourth a quarter as many, and so on.
YOUR CAT CAN’T PREDICT EARTHQUAKES (SCIENTISTS CAN’T EITHER)
Does your Aunt Janey say her cat predicts earthquakes? That’s nice—but know that scientists discount these types of stories. Of course, scientists can’t predict earthquakes either. Earthquakes occur as essentially random events, but humans resist randomness. We are driven to try to predict, control, or tie events to a specific cause, so we rapidly begin thinking magically when confronted by forces beyond our understanding or control. You can believe in kitty’s power if you’d like, but don’t count on your cat to warn you that Cascadia is coming.
In some other countries, you can hope to get a notification from an earthquake early warning (EEW) system, though: Japan and Mexico both have a network of sensors to provide immediate warning when an earthquake is coming. Text alerts give people enough time to find a safe place to drop, cover, and hold on, and equipment that could pose dangers during shaking is automatically shut off. But even with fully developed alert systems, the best we can hope for is an alert that reaches us seconds, not minutes or hours, before an earthquake begins.
On the West Coast, an EEW system called Shake Alert is being implemented by the US Geological Survey (USGS) and partners to provide similar alerts to our region. Currently, the system is being tested in California. Only about 50 percent of the sensors needed to provide alerts throughout the region are in place as of January 2020, and California is ahead of Oregon and Washington in implementation. A lack of dedicated funding to finish and operate the system, as well as technical problems complicating the delivery of alert messages, have slowed full implementation. No one knows how long it will take to overcome these barriers—or if Shake Alert will be operational before the next Cascadia earthquake.
HEED THE JOLT
“Did you feel that?” Most people will spend those valuable seconds of warning asking each other that question—and pondering the cause—when what they just felt was nature’s early warning that a 9.0 Cascadia earthquake has begun. Generally, when the plates “unlock” in a subduction zone earthquake, there is a seismic bump that may feel like a jolt—like a car has run into the building you are in or a crane has dropped a load of steel onto a nearby road—then the waves of energy that make the ground move begin. In many places there will be 10 to 15 seconds between this jolt and the arrival of the shaking.
Instead of looking out the window (the most dangerous place to be in an earthquake) to find the source of the disturbance, know that it’s time to drop, cover, and hold on—and to shout to others to follow your lead. If it actually is a car that ran into the building, you may feel slightly embarrassed by your mistake, but if it is the Cascadia earthquake, you may have saved others from injury or death.
EARTHQUAKE ODDS
After decades of answering questions about the odds of an earthquake occurring and seeing how people respond to the information, Dr. Lucy Jones now resists talking about the probabilities of an earthquake occurring on a fault. The founder and chief scientist at the Center for Science and Society, and the most recognized seismologist in California, prefers to simply note that the chances are 100 percent, given enough time.
We know a 9.0 Cascadia earthquake will occur in our region. The only thing we don’t know is when—and, thus, how much time we have to get ready for it. The current estimates of scientists is that, in the next fifty years, there is a roughly one-in-ten chance of a 9.0 earthquake along the full Cascadia subduction zone, or about a one-in-three chance of an 8.0 event. Human nature’s desire to calm ourselves means we translate these odds into reassurance that we have plenty of time. Yet every scientist in the field affirms that it is entirely possible for a 9.0 Cascadia earthquake to happen tomorrow. They emphasize that the time to get ready is right now.
DON’T BET ON THE ODDS
On July 4, 2019, a 6.4 earthquake struck in Ridgecrest, California, a sparsely populated area 122 miles northeast of Los Angeles. Dr. Lucy Jones noted that there was about a 5 percent chance that the earthquake was a foreshock rather than the main shock; a larger earthquake could follow. No one seemed to pay much attention to that—after all, the chances were 95 percent that the main earthquake had already occurred. On July 5, 2019, a 7.1 earthquake struck on the same fault. The earlier earthquake had, indeed, been a foreshock.
The first question most people ask about a potential earthquake is what the odds are that it will occur—an effort to assess whether to get ready based on how high the risk is. But rather than focusing on risk, we should look at consequences. The odds of any terrible event happening—a car accident, a serious medical condition—may be quite low, but the consequences of not having insurance against these events could be astronomical. Being two-weeks-ready is simply insurance against the consequences of a catastrophic earthquake.
THE ODDS THAT COUNT
More than 99.95 percent of people outside the coastal tsunami zone will likely survive a 9.0 mega-earthquake, based on estimates from a variety of scenarios.
Without preparation, there will be more entirely preventable deaths after such an earthquake—dehydration, waterborne illness, fatal inhalation of smoke or toxic fumes, hypothermia, and untreated medical conditions—than caused by the earthquake and tsunami.
Preventable suffering will be exponentially greater than necessary for the unprepared—like the difference between a difficult two-week camping trip in bad weather with short supplies and two weeks of being lost in the woods with nothing at all, struggling to survive.