• After the Big One: Can You Imagine America Without Los Angeles?

    The San Andreas Fault is Not Messing Around

    Earthquakes are happening constantly around the world. The seismic network that measures earthquakes in Southern California, where I live and spent my career as a seismologist, has an alarm built into it that goes off if no earthquake has been recorded for twelve hours—because that must mean there’s a malfunction in the recording system. Since the network was put into effect in the 1990s, Southern California has never gone more than twelve hours without an earthquake.

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    The smallest earthquakes are the most common. Magnitude 2s are so small they are felt only if someone is very nearby their epicenter, and one happens somewhere in the world every minute. Magnitude 5s are big enough to throw objects off shelves and damage some buildings; most days a few of these strike somewhere. The magnitude 7s, which can destroy a city, occur more than once a month on average, but luckily for humanity, most take place underwater, and even those on land are often far from people.

    But for more than three hundred years, none of these, not even the tiniest, has occurred on the southernmost part of the San Andreas Fault.

    Someday that will change. Big earthquakes have happened on the southern San Andreas in the past. Plate tectonics hasn’t suddenly stopped; it is still pushing Los Angeles toward San Francisco at the same rate your fingernails grow—almost two inches each year. Even though the two cities are in the same state and on the same continent, they are on different tectonic plates. Los Angeles is on the Pacific plate, the largest of the world’s tectonic plates, stretching from California to Japan, from the Aleutian Arc of Alaska to New Zealand. San Francisco is on the North American plate, which extends east to the Mid-Atlantic Ridge and Iceland. The boundary between them is the San Andreas Fault. It is there that the two plates get carried slowly past each other; their motion cannot be stopped any more than we could turn off the sun.

    In a strange paradox, the San Andreas produces only big earthquakes because it is what seismologists consider a “weak” fault. It has been ground so smooth, across millions of years of earthquakes, that it no longer has rough spots to stop a rupture from continuing to slip.

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    To understand the mechanics of it, imagine you’ve laid a large rug on the floor of a room that has wall-to-wall carpeting. After placing it, you decide that, on second thought, you want to move it one foot closer to the fireplace. If it had been laid on a hardwood floor, it would be easy enough to move: you could simply grab the side nearer to the fireplace and pull. But it’s on carpeting, so the friction between the carpet and the rug makes that impossible. What could you do? You could go to the far side of the rug, pick it up off the carpeting, and put the edge of the rug where you want it, a foot closer to the fireplace. You now have a big ripple, which you could push across the rug until you’ve reached the end, at which point the entire rug would be one foot closer to the fireplace.

    The San Andreas Fault has been smoothed to such a degree that now, when an earthquake begins, there is nothing left to keep it small.

    In an earthquake, a seismologist sees not a ripple but a rupture front. The motion of that ripple across the “rug” of the San Andreas Fault creates the seismic energy that we experience as an earthquake. It is a temporary local reduction in friction, allowing a fault to move at lower stress. In the same way that the rug couldn’t move all at once, an earthquake too must begin at one particular spot on its surface, its epicenter, and the ripple must roll across it for some distance.

    The distance the rupture front travels is one of the chief determinants of an earthquake’s size. If it moves a yard and stops, it is a magnitude 1.5 earthquake, too small to be felt. If it goes for a mile down the fault and stops, it’s a magnitude 5, causing a little damage nearby. If it goes on for a hundred miles, it is now a magnitude 7.5, causing widespread disruption.

    The San Andreas Fault has been smoothed to such a degree that now, when an earthquake begins, there is nothing left to keep it small. The ripple will continue to move down the fault, radiating energy from each spot it crosses, creating an earthquake that lasts for a minute or more and a magnitude that grows to 7 or even 8. Only after such an earthquake has broken the fault and made new jagged edges can it begin to produce smaller, less damaging earthquakes.

    So we wait for that big earthquake. And wait.

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    The southernmost part of the fault had its last earthquake sometime around 1680. We know this because it offset the edges of Lake Cahuilla, a prehistoric lake in much of what is now the Coachella Valley, filling with water the flats where the Coachella music festival meets each year. It left behind geologic markers, as did previous earthquakes, so we know that there were six earthquakes between AD 800 and 1700. That means the 330 years since the last earthquake on this part of the San Andreas is about twice the average time between its previous earthquakes. We don’t know why we are seeing such a long interval. We just know that plate tectonics keeps on its slow, steady grind, accumulating more offset and energy to be released the next time. Since the last earthquake in Southern California, about twenty-six feet of relative motion has been built up, held in place by friction on the fault, waiting to be released in one great jolt.

    Someday, maybe tomorrow, maybe in a decade, probably in the lifetimes of many people reading this book, some point on the fault will lose its frictional grip and start to move. Once it does, the weak fault, with all that stored energy, will have no way of holding it back. The rupture will run down the fault at two miles per second, its passage creating seismic waves that will pass through the earth to shake the megalopolis that is Southern California. Maybe we will be lucky and the fault will hit something that can stop it after only a hundred miles or so—a magnitude 7.5. Given how much energy is already stored, however, many seismologists think it will go at least two hundred miles, and thus register 7.8, or even 350 miles and reach 8.2.

    If it ruptures as far as central California, all the way to the section of the fault near Paso Robles and San Luis Obispo, it will hit a part of the San Andreas that behaves differently. This part accumulates a fingernail-growth rate of tectonic offset, just like the rest of the fault. But it’s what is known as a “creeping section.” Instead of storing energy to release in one big earthquake, the energy here oozes in small motions, sometimes with little earthquakes, sometimes with no seismic energy at all. We think, we hope, that the creeping section will act as a pressure valve of sorts, keeping the earthquake from growing any bigger than 8.2.


    In 2007–8, as science advisor for risk reduction at the U.S. Geological Survey, I led a team of more than three hundred experts in a project we called ShakeOut, to anticipate just what such an earthquake will be like. We created a model of an earthquake that moves across the southernmost two hundred miles of the San Andreas, extending from near the Mexican border to the mountains north of Los Angeles—a likely outcome, though still short of the worstcase scenario.

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    In the earthquake we modeled, we found that Los Angeles would experience intense shaking for fifty seconds (compare this to the seven seconds of the Northridge earthquake in 1994, which caused $40 billion of damage). A hundred other neighboring cities would as well. Thousands of landslides would cascade down the mountains, blocking our roads, burying houses and lifelines.

    Of the results we projected, one of the most frightening was the impact of fires triggered by the earthquake.

    In our model, fifteen hundred hundred buildings collapsed and three hundred thousand were severely damaged. We know which ones. They are the types of buildings that have collapsed in other earthquakes in other locations, and which we no longer allow to be built. But we have not forced existing buildings to be retrofitted to accommodate what we know. We might see some high-rise buildings collapse. The 1994 earthquake in Los Angeles and the 1995 earthquake in Kobe, Japan, exposed a flaw in how steel buildings had been constructed, causing cracks in their steel frames. Those buildings are still standing in downtown Los Angeles. We are going to see many brand-new buildings “red-tagged,” too dangerous to enter and in need of major repairs or demolition. Our building codes do not require developers to make buildings that can be used after a major earthquake, only buildings that don’t kill you. If the code works as it is supposed to, about 10 percent of the new buildings constructed to the latest code will be red-tagged. Maybe 1 percent will have partial collapse. A 99 percent chance of not collapsing is great for one building, but accepting the collapse of 1 percent of the buildings in a city with a million buildings is a different matter. The earthquake will probably not kill you, but it will likely make it impossible for you to get to work—for a very long time.

    Of the results we projected, one of the most frightening was the impact of fires triggered by the earthquake. Earthquakes damage gas lines; break electrical items and throw them onto flammable fabrics; spill dangerous chemicals; and generally have many, many ways of starting fires. Two of the biggest urban earthquakes of the twentieth century were the 1906 San Francisco and 1923 Tokyo (Kanto) earthquakes. Both set off fires that turned into firestorms and burned down much of those cities. Some people think that modern technology has solved much of the fire problem because the two big California earthquakes of the late twentieth century, the 1989 Loma Prieta earthquake in San Francisco and the 1994 Northridge earthquake in Los Angeles, did not lead to devastating fires. This is a mistake. Not because technology hasn’t changed, but because, in the eyes of seismologists, Loma Prieta and Northridge were not big earthquakes. Those who lived through them may disagree, and the damage they inflicted on those cities is undeniable. But these people simply don’t know what a really big earthquake will be like.

    What seismologists call “great” earthquakes (magnitude 7.8 and larger) are not just about stronger shaking—they are also about much larger areas. Loma Prieta and Northridge caused their strongest shaking near their epicenters, neither of which was in an urban core. Loma Prieta’s was in the Santa Cruz Mountains; the strongest shaking of Northridge was felt in the Santa Susana Mountains. Even so, more than a hundred significant fires broke out in each of those earthquakes. They were fought through mutual aid. San Francisco and Los Angeles put out calls for help, and firemen from other jurisdictions poured in to help. Citywide fires were averted because of the amazing, courageous work of firemen from across the region.

    When an earthquake like the one we modeled happens, every city of Southern California will have fires that need to be fought. Calls for help will be answered with desperate pleas for help in return. Aid will have to come from Northern California, Arizona, and Nevada. Those firemen will have to come to Southern California from the other side of the San Andreas Fault, which will have moved twenty to thirty feet, offsetting all the highways into the region. Those responders will struggle, maybe for days, to bring equipment across broken roads. The firemen who are here will be sent to fight fires in places where the pipes feeding the fire hydrants have broken and gone dry. Our analysis, reviewed by the fire chiefs who had led the firefighting in Northridge and Loma Prieta, concluded that the fires would double the losses of the earthquake, in terms of both economic impact and casualties. Sixteen hundred fires could break out, twelve hundred growing large enough to require more than one fire company. We don’t have that many fire companies in all of Southern California.

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    As bad as this picture looks, it could be worse. In ShakeOut, I got to specify the weather. I made it a cool, calm day. Unfortunately, I don’t get to do this for the real thing. If the earthquake happens during the infamous Santa Ana winds, which have spread great Southern California wildfires and caused billions of dollars in losses, the fires that get started may be unstoppable.

    Most of us will survive. Our estimate was that eighteen hundred people will die and fifty-three thousand will need emergency medical care. A significant number of hospital beds will be out of commission as hospitals suffer their own damage. And it will be very difficult to get to them. Bridges will be impassable, collapsed buildings will leave rubble in the street, and power will be knocked out, darkening traffic lights. Many people will be trapped in buildings; first responders will be overwhelmed. Most victims will be rescued by their neighbors. Losses will exceed $200 billion.

    Life will not return to any semblance of normality for quite some time for the residents of Southern California. In the following months, tens of thousands of aftershocks will occur, some of which will be damaging earthquakes in their own right. The systems that maintain urban life—electricity, gas, communication, water, and sewers—will all be broken. The transport systems that bring food, water, and energy into the region all cross the San Andreas and will be cut. In a simpler world, when you lose your sewer system, you build a temporary outhouse in the backyard. In the dense urban environment of a modern city, a lack of sewers is a potentially catastrophic public health crisis. Cities are possible because of the complex engineering systems that support life. Those will be lost in such an earthquake.

    Half of the total financial losses in our model were from lost business. A beauty salon cannot reopen without water. Offices cannot function without electricity. Tech workers cannot telecommute without Internet capabilities. Retail stores struggle if their clerks and customers don’t have the means of transportation to get there. Gas stations cannot pump gas without electricity and cannot take your credit card if they’re not online. And how many of us will want to stay in Los Angeles, much less go to work, when none of us have had a shower in a month?

    Here we reach the limit of our technical analysis. Our scientists and engineers and public health experts can estimate buildings down, pipes damaged, legs broken, transportation disrupted. But the future of Southern California is the future of communities. We know what will happen to its physical structure, but what will happen to its spirit?


    Natural disasters have plagued humanity throughout our existence. We plant farms near rivers and near the springs that form along faults, for their access to water; on the slopes created by volcanoes, for their fertile soil; on the coast, for fishing and trade. These locations put us at risk of disruptive natural forces. And indeed we are familiar with the occasional flood, tropical storm, passing tremor. We learn how to construct levees, perhaps a seawall. We add some bracing to our buildings. We are not quite so scared after the tenth minor quake. We begin to feel confident that we can control our natural world.

    Natural hazards are an inevitable result of the earth’s physical processes. They become natural disasters only when they occur within or near human construction that fails to withstand the sudden change they wreak. In 2011, a magnitude 6.2 earthquake occurred in Christchurch, New Zealand, killing 185 and causing roughly $20 billion in losses. Yet an earthquake of that size happens every couple of days somewhere in the world. This relatively minor earthquake became a disaster because it occurred right under the city, and the buildings and infrastructure were not built strong enough to withstand it. Natural hazards are inevitable; the disaster is not.

    I have spent my professional life studying disasters. For much of my career, I was a researcher in statistical seismology, trying to find patterns and make sense of when and how earthquakes occur. Scientifically, my colleagues and I could prove that compared to human timescales, earthquakes occurred randomly. But we found that “random” was an idea we could not convince the public to accept. So, recognizing that the desire for prediction was really a desire for control, I shifted my science toward predicting the impact of natural disasters. My goal was to empower people to make better choices—to prevent the damage from happening in the first place.

    The U.S. Geological Survey, the government agency charged with providing the science about geological hazards, was my lifelong professional home. In a pilot project in Southern California, and later for the nation, we studied floods, landslides, coastal erosion, earthquakes, tsunamis, wildfires, and volcanoes, with the objective of connecting communities to the scientific information that could make them safer, whether it was predicting landslides during rainstorms, recommending wildfire control in ecosystem management, or better judging our priorities when it comes to mitigating the risk of a big earthquake.

    I was also one of the scientists who provided information to the public after earthquakes. I found people were desperate for science, but often not for the reason I expected. I saw the ways it could be used to halt the damage. But in times of natural disaster, the public turns to scientists to minimize not just destruction but also fear. When I gave the earthquake a name and a fault and a magnitude, I inadvertently found myself serving the same psychological function as priests and shamans have done for millennia. I was taking the random, awesome power of Mother Earth and making it look as though it could be controlled.

    Natural disasters are spatially predictable—where they occur is not random. Floods happen near rivers, big earthquakes (generally) strike along big faults, volcanic eruptions take place at the site of existing volcanoes. But when they happen, especially compared to human timescales, is random. Scientists say an occurrence is “random about a rate.” That means we know, in the very long term, how many of them take place. We know enough about a fault to know that earthquakes occur—have to occur—with a certain frequency. We can study a region’s climate to the extent that its average rainfall becomes predictable. But whether this year brings floods or drought, whether the largest earthquake along the fault this year is a magnitude 4 or 8—that is purely random. And we humans don’t like it. Random means every moment presents a risk, leaving us anxious.

    Psychologists describe a “normalization bias,” the human inability to see beyond ourselves, so that what we experience now or in our recent memory becomes our definition of what is possible. We think the common smaller events are all that we have to face, and that, because the biggest one isn’t in anyone’s memory, it isn’t real. But in the earthquake that ruptures through the full length of a fault, the flood described as Noachian, the full eruption of a volcano, we see more than the common disaster. We face catastrophe.

    In that catastrophe, we discover ourselves. Heroes are made. We laud the quick thinking, the unquenchable will to survive. We see extraordinary acts of courage committed by ordinary people, and we praise them for it. The firemen who run into a burning building when everyone else is running out hold a special place of honor in our society. Disaster movies always have as their hero the daring responder, from Charlton Heston in 1974’s Earthquake, to Tommy Lee Jones in the 1997 film Volcano, to Dwayne “The Rock” Johnson in 2015’s San Andreas. There is likewise a villain, in the public official who covers up the warning, or a selfish, scared victim who claims the last lifeboat for himself.

    We have choices to make, right now, that could make our cities much more likely to survive and recover from these great natural disasters when they strike.

    We show compassion for the victims, knowing that we could have been the one hit. Indeed, it is the randomness of the victimization that forms much of our emotional response, that encourages generous donations. For many people, helping the victims serves as a sort of unconscious good luck charm, warding off the same fate for themselves. We pray to God to protect us from the danger.

    When the prayers fail and the catastrophe is upon us, we seem incapable of accepting that it is inexorably, infuriatingly random. We turn to blame. For most of human history, the great disasters have been seen as a sign of the gods’ displeasure. From the biblical Sodom and Gomorrah to the devastating earthquake of 1755 in Lisbon, those who survived, those who witnessed, declared that the victims were being punished for their sins. It allowed us to pretend that we could protect ourselves by not making the same mistakes— that we had no reason to fear the bolt out of the blue.

    Modern science may have changed many of our beliefs, but it hasn’t swayed our subconscious impulses. When that great Southern California earthquake finally strikes, I know two things will happen. First, rumors will spread that the scientists know that another earthquake is coming, but that we aren’t saying anything to avoid scaring the public. This is the all-too-human rejection of the random, an attempt to form patterns, to find reassurance. Second, there will be blame. Some will blame FEMA, accusing them of a poor response. Some will blame the government for allowing bad buildings to have been constructed (maybe even the same people who fought against mandatory improvements of those weak buildings). Some will blame scientists for not listening to that week’s earthquake predictor. Some, in a pattern we have seen for centuries, will blame the sinners of the hedonistic La-La Land.

    The last thing any of us will want to do is accept that, sometimes, shift just happens.

    Most cities have the potential for a Big One in their future. Those harbors, fertile fields, and rivers that make everyday life viable are there because of natural processes that can produce disasters. And that Big One will be qualitatively different from the smaller-scale disasters in our recent past. It is a disaster when your house is destroyed. It becomes a catastrophe when not just your home but your neighbors’ homes and so much of your community’s infrastructure are destroyed that societal functioning itself collapses. We have choices to make, right now, that could make our cities much more likely to survive and recover from these great natural disasters when they strike. We can make informed choices only if we consider our potential future, and if we take a hard look at our knowable past.

    With this book I tell the stories of some of the earth’s greatest catastrophes, and what they reveal about ourselves. Each was the Big One of its region, shifting the nature of that community. Together they show how our fear causes us to respond to random catastrophe—the reasoning we employ, the faith we manifest. We will see the limitations of human memory, which keeps us from believing that the one-in-a-million, or even the one-in-a-thousand, will ever affect us. And we will face the knowledge that our risk is growing. Because of the increasing density and complexity of our cities, more people than ever before are at a greater risk of losing the systems that maintain life.

    We will come to a place where all our defenses are stripped bare, forced to consider the kind of suffering without meaning that could crush a human spirit. Because in the end, we face disasters like everything else in our lives—searching for meaning. What is left when we are denied a scapegoat or the specter of divine retribution? Our cries of “Why now?” or “Why us?” may never be satisfactorily answered. But if we can look beyond meaning, we’ll find a question with profound moral implications: How, in the face of catastrophe, do we help ourselves and the people around us survive and make a better life?


    From The Big Ones by Lucy Jones. Copyright (c) 2018 by Lucy Jones. Published by permission of Anchor Books, an imprint of the Knopf Doubleday Publishing Group, a division of Penguin Random House LLC.

    Lucy Jones
    Lucy Jones
    Dr. Lucy Jones was a seismologist for the U.S. Geological Survey for thirty years, most recently as Science Advisor for Risk Reduction. She created the Great ShakeOut Drill, an earthquake preparation experiment that by 2016 included 53 million participants around the world. A research associate at Caltech, she holds a PhD in geophysics from MIT and a BA in Chinese language and literature from Brown University. She lives in Southern California.

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