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The ShakeOut Earthquake Scenario

Shakeout Earthquake Scenario

The Shakeout Earthquake Scenario. Image from U.S. Geological Service.

There is no debate among scientists about whether Southern California will experience a major earthquake. The question is when.

In 2008, the U.S. Geological Survey brought together a team of scientists, engineers and other professionals from their own agency, the California Geological Survey, Southern California Earthquake Center, and nearly 200 other partners in government, academia, emergency response, and industry to produce the “ShakeOut Scenario.” The project applied the best current scientific understanding to create a major earthquake scenario, meant for planning, training and identifying what could be done to minimize the catastrophic impact of such an earthquake in southern California.

The scenario envisioned a magnitude 7.8 earthquake on the southern San Andreas Fault, a location selected due to the amount of stored strain on that part of the fault, posing the greatest risk of imminent rupture. From there, seismologists and computer scientists modeled the ground shaking that would result. Engineers and other professionals then projected how that shaking would damage buildings, roads, pipelines, and other infrastructure. Social scientists and others projected casualties, emergency response, and impact on southern California’s economy and society. Although this was not considered the worst possible scenario, and only one realistic outcome, it is was a scenario worth preparing for and mitigating against.

Because the hypothetical ShakeOut Scenario was meant to be used for earthquake drills and emergency response exercises, it was assigned an arbitrary date, time and even weather conditions (the Almanac assigned new specific dates and times for our version below). It included plausible aftershocks and detailed numbers of casualties, collapsed structures and losses. Although this scenario is hypothetical, such a destructive eruption on the San Andreas Fault, as described, is not only considered highly probable, but even the most likely to occur anywhere in California.

The ShakeOut Scenario is not a prediction. Each earthquake creates unique patterns of shaking and damage and the next big earthquake will produce a different number of casualties and losses. What is entirely predictable, though, is that structures not built or reinforced to withstand intense shaking will be damaged or destroyed, as will every road, rail line, and pipe crossing the fault rupture. Also predictable is the widespread social and economic impact on the region. It is hoped that the ShakeOut Scenario, in addition to being used for earthquake drills and emergency response exercises, encourages southern Californians to be better prepared for a major earthquake of similar size.

The Scenario...

January 14

Thursday, 4:24 pm (...the quake begins)

Salton Sea

The Salton Sea in Imperial County. Image by Samboy via Wikimedia Commons.

The San Andreas Fault suddenly ruptures at Bombay Beach on the Salton Sea in Imperial County, sending shock waves racing along the fault at 2 miles per second. The ground on both sides of the fault is offset almost 44 feet. Within 30 seconds, the Coachella Valley experiences nearly a minute of strong shaking, inflicting serious damage. Ten miles of the 10 freeway are dismantled. The eastern portion of Riverside County is cut off the western portion.

Thursday, 4:25 pm (...1 minute after the quake began)

Freeway Collapse

Collapsed freeway structures. Image by Robert A. Eplett, FEMA.

The Los Angeles area is unaware of the event as the Coachella Valley lies devastated. The first waves hit the Cajon Pass, severing Interstate 15 in a number of places. Landslides cover roads and rail lines and other rail lines bend and break. A train descending through the pass derails. Roads are broken apart, separated by as much as 15 feet. The strong shaking hits the highly populated areas of Riverside and San Bernardino counties. The Coachella Valley continues to shake.

Thursday, 4:25:30 pm (...1 and a half minutes after the quake began)

Los Angeles Basin

Los Angeles Basin. Image by ArminEP via Pixabay.com.

30 seconds after hitting the Cajon pass, earthquake shock waves enter the Los Angeles Basin, shaking the region violently for 55 seconds. Many commuters in the Los Angeles area are heading home from work in slow moving freeway traffic. K-12 schools were out for the day and students are at home or heading home, or in after-school activities. Incoming earthquake waves are big and long and, although many structures manage to ride these like boats on a choppy sea, some simply cannot. Hundreds of old masonry buildings, older commercial and industrial concrete buildings, wood frame buildings and even five high-rise steel buildings collapse. Everything in homes, shops and offices that was not secured is overturned and thrown to the floor, leaving floors strewn with broken glass and ceramics, cords, liquids and other debris. Roads and airport runways are deeply cracked. Old warehouse districts and historic downtowns crumble. Hundreds of people are killed when structures collapse around them and thousands more are trapped inside. Newer homes suffer only minor damage, but many older wood-frame buildings and mobile homes are shifted from foundations, breaking gas and water lines. Five steel high-rises are collapsed and 10 others are determined unsafe to enter. Many unreinforced structures—typically those built before 1933— made of bricks, cinderblocks, or adobe, are destroyed. Many office buildings built in the late 1960s and early 1970s are severely damaged. Because workers were still in these buildings, thousands are injured and hundreds of deaths occur in workplaces. Water pours from broken water lines, flooding buildings and residences. Although some water lines continue to flow, warnings are issued not to use the water, due to possible contamination by broken sewer lines.

Damaged Utilities

Damaged utility poles and burning ruptured gas lines. Image from U.S. Geological Survey.

Fires break out everywhere. Electrical lines arc, gas lines leak, and chemicals are spilled and mix. Explosions occur as seeping gas makes contact with already burning fires. Throughout the Los Angeles area, 1,600 large fires are now burning simultaneously. Firefighters are unable to engage every fire. Even if firefighters happen upon a fire, they may be blocked from fighting the fire due to impassable roads, debris from collapsed structures, abandoned vehicles or downed utility lines. If they manage to get close to a fire, water pressure may be poor or non-existent due to broken water lines. Many fires therefore burn unimpeded and, in some cases, become conflagrations that engulf dozens of blocks. Some residents in stricken neighborhoods band together to try to fight small fires with garden hoses, provided they still have enough water pressure.

Damaged Apartments

Damaged apartments. Image from FEMA.

As many as 2,000 people are killed as a result of the earthquake, about 800 in collapsed structures. Others die mostly as a result of fires and accidents. Still-functioning hospitals are overwhelmed with 50,000 injured people.

Most homes and buildings are now without water or electricity. Surface streets become gridlocked with cars, trucks and buses as traffic lights no longer operate and electric trains are immobilized. Drivers that cannot move anywhere begin abandoning their vehicles for the long walk home. Cell phones become useless as cellular networks are jammed with callers. People trapped in elevators and buildings alternate between crying out for help and sitting to wait in hope of rescue. Because the event occurs during the winter, darkness without any light is not far off.

Destroyed Vehicles

Vehicles destroyed by fallen bricks. Image by Andrea Booher, FEMA.

Thursday, 4:26 pm (...2 minutes after the quake began)

The fault rupture stops near Palmdale, but the seismic waves continue north into Bakersfield, Oxnard and Santa Barbara. Throughout most of southern California, electrical power is out. Emergency generators that were secured are now the only source of electrical power. Although the shaking has ceased in the Coachella Valley, aftershocks begin there and occur throughout southern California. The continuing aftershocks, many large enough to feel, inflict some additional damage and add to the stress of an already traumatized population. Many people are separated from loved ones and concerned that they are unable to communicate with them. Some of those who made prior arrangements to contact and communicate through people living outside southern California manage to get through by telephone and obtain news about the status of separated family members.

Trying to Telephone Out

Woman trying to call out. Image by Fotografierende via Pixabay.com.

Although most state highways, having been retrofitted, survive intact, traffic deaths occur in crashes due to the intense shaking. Many local bridges and overpasses, not having yet been retrofitted, are damaged or destroyed. Hospital buildings have also survived, but, non-structural damage, such as damaged water pipes, leaves some hospitals nonfunctional.

Damaged Freeway

Damaged freeway. Image by Robert A. Eplett from FEMA.

Thursday, 4:29 pm (...5 minutes after the quake began)

Those who are able to get news from battery-operated radios, learn that the earthquake was a magnitude 7.8. The nation and the world turn its attention to southern California. News helicopters begin coverage of the devastation. With power out, people without radios talk to anyone they meet to get news. Surviving telephone systems, including 911, are unusable, overwhelmed by the sheer number of callers trying to get through.

Thursday, 4:54 pm (...30 minutes after the quake began)

Emergency operation centers are activating in every community. Police, fire and medical responders have shifted into major emergency mode, focusing on local incidents as best as they can.

U.S. Army Corps of Engineers Emergency Van

U.S. Army Corps of Engineering Mobile Van. Image from Defense Visual Information Distribution Services - Dvidshub.net.

As emergency responders do a "windshield survey" that involves rolling through neighborhoods to tally damage and identify areas of greatest need, they begin to see the extent of the tragedy. Hundreds of older buildings believed to be vulnerable to a major earthquake are indeed lying in rubble. Thousands of other structures, although still standing, are so badly damaged as to be forever uninhabitable.

Collapsed Home

Collapsed home. Image from FEMA.

People begin inspecting collapsed homes and buildings in their neighborhood to see if anyone is trapped or injured. If they find any running water with water pressure, they try to put out fires. When they have reason to believe people are trapped or injured in the wreckage of homes and buildings, even without proper gloves and tools, they try to pull debris away with bare hands. Most people who are rescued are rescued by fellow victims.

Rescue Worker

Rescue worker. Image by USAF TSGT Rob Marshall from NARA Archives, archives.gov.

Los Angeles International Airport and other local airports divert air traffic away from southern California.

Flight Over Los Angeles

Flight over Los Angeles. Derived from image by Alexman89, via Pixabay.com.

Anxiety builds as millions of people, having no pre-planned emergency communications plan, continue to be unable to contact family members, many of them children. These include many first responders, now fully engaged in search and rescue.

Rescue Workers Help Earthquake Victim

Rescue workers help earthquake victim. Image by MCS 2nd Class Justin Stumberg from U.S. Navy.

Engineers race out to inspect dams around southern California. Some are found showing signs of potential failure. Emergency responders, already spread thin, must now try to evacuate people in downstream areas that are threatened by a dam collapse. Fortunately, no dams actually fail in this particular earthquake.

Thursday, 4:57 pm (...33 minutes after the quake began)

A magnitude 7.0 aftershock erupts in the Salton Sea area, but, the waves move southward into relatively unpopulated areas. Firefighters from San Diego County who were preparing to convoy north to assist are diverted to respond to areas in their own county hit by the aftershock.

San Diego Firefighters

San Diego area firefighters. Image from County of San Diego.

Thursday, 6:24 pm (...2 hours after the quake began)

Burning Structure

Burning structure. Image by Kolyaeg via Pixabay.com.

A number of smaller fires that burned unimpeded have merged into conflagrations, engulfing dozens of blocks, especially in areas with a lot of wooden structures in close proximity. National and international media entities are now focused on urban Los Angeles and frequently showing a few severely damaged and collapsed structures. The media images make the overall damage appear much worse than it actually is. Firefighters and other emergency responders from Arizona and northern California mobilize to enter southern California, but, many key routes into the area are determined to be impassable. Functional hospitals are filled with injured victims that arrive or are brought in, but ambulances struggle to reach and transport victims.

Medical Workers

Medical workers attend to a patient. Image from U.S. Air Force.

January 15

Friday, 7:24 am (...14 hours after the quake began)


FEMA mobile unit. Image from FEMA.

The President has already issued a Disaster Declaration for southern California and Federal resources are committed. A Joint Incident Command Center is set up by the Federal Emergency Management Agency (FEMA), the California Governor’s Office of Emergency Services (OES), and other emergency management agencies. Because normal communication systems are unreliable, ham radio operators step in to assist emergency responders. People outside southern California continue to try to reach family and friends here, but few succeed.

Removing Belongings

Residents salvaging belongings from damaged apartment. Image from FEMA.

Friday, 8:41 am (...15+ hours after the quake began)

As if the Los Angeles area hasn’t had enough, a massive magnitude 7.2 aftershock erupts near San Bernardino and the rupture moves west along the base of the San Gabriel Mountains, stopping after 18 miles near Monrovia, east of Pasadena. The aftershock inflicts yet more damage to already-weakened infrastructure and overextended emergency resources. The aftershock triggers even more aftershocks, causing yet more damage.

Destroyed Apartment

Destroyed apartments. Image from FEMA.

Friday, 4:24 pm (...24 hours after the quake began)

Utility companies work non-stop to restore electricity, water and gas service. Large areas, however, especially those hit with the most shaking, continue without basic utilities. Utility workers, like emergency responders, drive forward with their work despite personal concerns about their own families.

Donations arrive from all parts of the country. Red Cross and other shelters open at schools and other undamaged public centers, distributing food, water, and essential personal items. Many, if not most people, are camping outdoors.

Red Cross Assistance

Red Cross distributes food and assistance. Image by Robert A. Eplett, FEMA.

Some families are finally able to reunite. Emergency responders use helicopters and whatever means to move around more quickly. For people in general, bicycles and four-wheel-drive vehicles become important modes of transportation.

January 16

Saturday, 5:56 am (...2+ days after the quake began)

Stressed Person

Person stressed by events. Image by Kate Jayne via Pexels.com.

A magnitude 5.7 aftershock occurs with the epicenter in Rialto.

Fearful rumors (such as widespread looting, dead bodies causing disease outbreaks, an impending much larger earthquake, and authorities withholding information), although unfounded, are prevalent.

January 17

Sunday (...3 days after the quake began)

People outside southern California are beginning to be able to contact friends and family here. Search and rescue teams are still making rescues, but finding fewer survivors. Most major fires are extinguished, except super-conflagrations (merged conflagrations consuming hundreds of blocks).

Rescue Workers With Search Dogs

Rescue workers with search dogs. Image by C.E. Meyer from U.S. Geological Survey.

Many medical staff members have worked without sleep since first responding to the disaster.

Open-air trauma centers are operating adjacent to evacuated hospitals that were seriously damaged. There is a shortage of medical equipment such as kidney dialysis machines. Some patients are evacuated to hospitals in other parts of California and to Nevada and Arizona. The patient load at Los Angeles area hospitals is unevenly distributed, with some hospitals overloaded, while others receive few patients.

Mobilized National Guard units assume some specialized, earthquake-related law enforcement duties, allowing local law enforcement to resume normal law enforcement operations. Fear of widespread looting, stoked by media reports and rumors, begins to subside. Police and security personnel secure damaged structures, but tenants and owners are allowed some controlled and limited access.

National Guard

California National Guard exercise police duties. Image from California State Guard, Wikiwand.com.

February 12

Friday (...30 days later)

Most power and gas utility services are restored and most major roads are reopened. Piles of debris, however, line the roads. Landfills are filled with millions of tons of debris. Local bridges that were damaged or destroyed cut off some local roads. Some damaged freeway sections also remain closed for repairs. Many long distance commuters are unable or unwilling to return regularly to work. Tens of thousands of people remain without permanent shelter or jobs—or both.

Without Shelter

Thousands of people who lost homes find shelter. Image by Andrea Booher from FEMA.

Where earthquake damage was not severe, most water service is restored. Residents with running tap water, however, are cautioned to boil their water before use, due to confirmed or possible contamination, especially in areas with damaged sewer systems. Water systems will not be certified as safe for a year or more. Some sewer systems remain under repair.

Toilets in scattered areas still cannot be flushed due to damaged sewer pipes. Near the fault, although plenty of water is available, it still cannot reach some homes, schools and businesses. Some communities decide that, rather than try to find and repair numerous breaks in their damaged water system, it would be faster and less costly and to just replace the entire system. Orders for water pipes and connectors become so backlogged that debate arises over which orders should be prioritized.

Scrapped Damaged Water Pipes

Scrapped damaged water pipes. Image from PxHere.com.

In places with minimal structural damage and water service, businesses reopen, however, most lost computers, stock, and files to fire or flooding. Businesses that carried earthquake insurance are better positioned to move forward. Some face problems reconnecting with former suppliers, not to mention former customers and employees. Manufacturers struggle with delays and additional costs for transporting products out of southern California. The local economy faces a prolonged struggle to return where it was before the earthquake.

Closed Property

Closed property. Image by J.K. Nakata from the U.S. Geological Survey.

Because of the loss of homes, jobs, and schools, some residents decide to leave southern California to stay with family or friends elsewhere. Most still expect to return.

Almost all public K-12 schools and community colleges are reopened. Unlike universities and private schools that were not subject to strict building codes, public school facilities suffered relatively little structural damage. Yet they still struggle to replace damaged furniture, equipment and supplies. At the same time, some families have relocated or are keeping their children home, thus reducing class sizes. Some teachers have not returned. Universities and private schools, having suffered more significant damage than public schools, are struggling to reopen. Some university students transfer to less damaged schools or outside southern California.

Damaged Classroom

Damaged classroom. Image from the U.S. Geological Survey.

The earthquake inflicted a terrible toll on the Los Angeles area. The cost to Southern California is 2,000 deaths, 50,000 injuries, and $200 billion in damage.

July 14

Wednesday (...6 months later)

Water is again running in homes, schools and businesses across the region. Many businesses, however, especially smaller businesses with less resources, have been forced to close. Closing businesses create a domino effect and, as jobs disappear and become less available, increasing numbers of people are struggling economically.

Some faith communities have also been forced to disband, due to severely damaged houses of worship and dwindling congregations.

Damaged Church

A seriously damaged church. Image by Petr Kratochvil via PublicDomainPictures.net.

Competition for building materials and construction crews is fierce. Communities that proactively planned for a disaster, see rebuilding well underway. Other communities with less expeditious building procedures and paperwork struggle to launch post-disaster reconstruction.

Many multi-family residences throughout the region still remain uninhabitable, with tenants still living outdoors.

Temporary Shelter

Temporary shelter using a FEMA-supplied tent. Image from FEMA.

As businesses close and people give up trying to recoup losses, financial institutions find themselves with a growing number of loans in default.


Homes foreclosures. Image from U.S. Bureau of Labor Statistics.

2 Years Later

How this story turns out depends on us. We begin writing this story by how we prepare for this scenario now.

More information on the science behind this project at The ShakeOut Scenario .

Source: The ShakeOut Earthquake Scenario—A Story That Southern Californians Are Writing - U.S. Geological Service

Earthquake, Disaster
Know What To Do - Before, During & After a Major Earthquake

See Forecasting California’s Earthquakes—What Can We Expect in the Next 30 Years?, U.S. Geological Survey Fact Sheet 2008-3027.