But what gets less attention is the aftermath of such a huge quake, which could leave whole neighborhoods uninhabitable and hundreds of thousands of people without homes.
Officials are trying to determine where all those refugees would go.
In the San Francisco Bay Area, more than 400,000 could be displaced in a magnitude 7 earthquake on the Hayward fault, which runs underneath cities like Berkeley, Oakland, Hayward and Fremont, said Ken Hudnut, the U.S. Geological Survey’s science adviser for risk reduction. And it’s possible that more than 250,000 people in Southern California could be forced out of their homes after a major earthquake on the San Andreas Fault, Hudnut said.
Not everyone would have to stay in public shelters. Many would stay with relatives, friends and hotels. Still, more than 175,000 people might have no choice other than stay at public shelters in Southern California, which could be challenged with acute shortages of food, water and medicine, according to ShakeOut, a USGS report simulating a major Southern California earthquake.
And in the Bay Area, so many buildings built under minimal codes could be so damaged that many may be forced to move away “for at least several months, and possibly permanently” because of the region’s housing shortage, according to a separate USGS report on a hypothetical Northern California earthquake.
“So many people will be displaced they won’t be able to stay within the metro area,” Keith Porter, a University of Colorado Boulder professor and chief engineer of the USGS earthquake reports, said of a major Bay Area earthquake. “So they’ll move away, just like they moved away from New Orleans after Hurricane Katrina.”
Arizona recently took a major step in dealing with this question. Officials in May launched a full-scale exercise that simulated the arrival of 400,000 evacuees from Southern California. The drill gave emergency workers a chance to consider how they would respond to the many elements of the disaster: providing food and shelter, helping unaccompanied minors, assisting in family reunification, and dealing with transportation and resource problems.
The exercise was aimed at beginning to think about how to deal with such a refugee crisis, though experts in California said it’s unlikely that many people would end up in Arizona. It might be quite difficult to leave California after an earthquake moves one side of the San Andreas past the other by as much as 30 feet, severing routes to Phoenix on Interstate 10 in the Coachella Valley and Las Vegas on Interstate 15 at the Cajon Pass.
Complications would be a widespread lack of power, thwarting the ability of motorists to refuel. “If you choose to go, it’s going to be difficult to do so. It’s a pretty hot desert between you and Phoenix,” seismologist Lucy Jones said.
In the hypothetical magnitude 7.8 earthquake on the San Andreas Fault, many people living in eastern Los Angeles County, Riverside, San Bernardino and the desert cities of the Coachella Valley would probably leave for less-affected areas.
But even in Southern California, it would be hard to move around. Streets would be clogged with debris, traffic lights wouldn’t work and bridges would be damaged, the USGS says.
Experts said it probably won’t be necessary for quake refugees to go all the way to Arizona or Nevada. Even if a magnitude 7.8 earthquake hits the southern San Andreas, areas farther from the fault would still be habitable, such as Orange, Ventura and San Diego counties, Jones said.
“There’s going to be a lot of Southern California that’s not going to be devastated,” Jones said.
Which areas would be most affected depends on which fault ruptures. A magnitude 7.5 earthquake on the Puente Hills thrust fault directly underneath downtown Los Angeles would be catastrophic there, but would leave Riverside in better shape.
Experts say it would be much better to shelter in place at home. Owners can prepare to do so by retrofitting older houses or apartments at risk of sliding off their foundations or collapsing in an earthquake. Residents can prepare by storing water, food, medicine and other supplies to sustain themselves for, ideally, two weeks, or at least 72 hours. A gallon of water per day per person is recommended.
But most Californians don’t prepare, and not stocking up on something as basic as drinking water could lead residents to leave even if their homes are structurally sound.
“It’s clear the public doesn’t think about these things,” Hudnut said. “I’d rather be one of those people who doesn’t have to go and has more water stored.”
But a wild card that would push people to flee is fire after an earthquake, with shattered pipes making firefighting difficult.
Most hydrants in the East Bay would be dry in a magnitude 7 earthquake on the Hayward fault, the USGS says, helping to allow fires to burn a building floor area equal to 52,000 single-family homes. In Southern California, it’s possible the equivalent of 133,000 single-family homes would be charred.
In three great urban earthquakes in modern history — Lisbon in 1755, San Francisco in 1906 and Tokyo in 1923 — the fires after the earthquakes were particularly devastating.
“The fires were overwhelming,” said Jones, author of “The Big Ones: How Natural Disasters Have Shaped Us and What We Can Do About Them.” “If the firestorms are getting going, and we’re going into Santa Ana conditions, and they haven’t been able to control the fires,” it’s possible that people may seek to flee to other states, Jones said.
But states like Arizona could have other problems than just dealing with evacuees. Those states could suffer fuel shortages from the severing of pipelines in California where they cross the San Andreas Fault, Jones said.
While California may have to deal with a short-term shelter crisis, a longer-term concern is whether so many people move away permanently that communities wither, jobs are lost and businesses shutter, Jones said.
The only years that L.A. has ever lost population were the two years after the 1971 Sylmar and 1994 Northridge earthquakes, Jones said.
The 3 1/2 day simulation near Phoenix — planned over a year, involving 75 agencies and more than 1,000 people — first focused on Arizona counties closest to California’s border.
“They will be the first to experience fuel or food shortages, cellphones getting overloaded and a medical surge,” said Judy Kioski, spokeswoman for the Arizona Department of Emergency and Military Affairs. “We’re worried about where are people going to shelter, how do we feed them, and family reunification.”
The exercise included mass of tents on a field near Phoenix simulating a shelter; some people acted as evacuees, others practiced how to render aid.
Some lessons have already been learned. “One of the things we identified was turning rest areas into locations where we could have additional information, and providing hard copies of information if cellphones go out,” Kioski said.
Previous drills have taken place in Utah, where the Wasatch fault zone threatens the Salt Lake City area with earthquakes as large as magnitude 7.5, and Missouri, where the New Madrid Seismic Zone generated several earthquakes between magnitudes 7 and 8 in the winter of 1811-12.
In California, officials have conducted their own emergency simulations and drills. Recently, a simulation was held envisioning a tsunami wiping out roads in Humboldt and Del Norte counties, and officials flew C-130 aircraft and helicopters in an exercise to test how supplies could be flown in and which airports could be accessible, said Kelly Huston, a deputy director of the California Governor’s Office of Emergency Services.
In September, the Bay Area will undergo its annual Urban Shield training, which tests the region’s response capabilities in a disaster. This year, the exercise will focus on mass care and sheltering.
Elements of emergency plans have already been used. When more than 100,000 people were ordered evacuated downstream of Oroville Dam last year lest an emergency spillway collapsed, officials opened evacuation centers, including one in Sacramento.
But one lesson that has been learned is that most people aren’t inclined to flee long distances, as was the case in the Wine Country wildfires last year.
“We found most people want to stay near to or close to their homes,” Huston said, even if it meant pitching tents in front of damaged properties. That means a key priority may be, for example, “to provide food and assistance to neighborhood by neighborhood.”
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