As residents of one of the world’s most seismically active regions, many of us harbor concerns about the possibility of a large earthquake hitting San Francisco.
Whether it’s when we're taking BART between Embarcadero and West Oakland, driving over the Bay Bridge, or sleeping in our early 20th century brick homes, the thought of “the big one,” however fleeting, has crossed each and every one of our minds at one point or another.
Blockbuster films like "San Andreas" paint images of what a disaster might look like in our city; however, if we ditch the Hollywood drama, over-the-top CGI, and Dwayne Johnson, what would a large-scale earthquake really look like in San Francisco today?
In light of the anniversary of the Great 1906 Earthquake, 110 years ago today, as well as recent earthquakes in Japan and Ecuador, we decided to take a closer look at what would happen if the earthquake that brought San Francisco to its knees in 1906 struck today.
On the morning of April 18th, 1906, at approximately 5:12am, an earthquake struck San Francisco. Although decades before the creation of the Richter Scale, experts estimate that the earthquake, with an epicenter just off the coast, registered between 7.8 and 8.3. (The 1989 Loma Prieta earthquake, for comparison, was a 6.7 and originated near Santa Cruz.)
The earthquake’s shock was felt over an area of roughly 375,000 square miles — roughly eight times greater than that of the 1989 Loma Prieta Earthquake — from Coos Bay, Oregon, all the way to Los Angeles, and as far east as central Nevada. Destruction was targeted in the Bay Area but extended from the southern part of Fresno County to Eureka, stretching between 25 and 30 miles on either side of the San Andreas Fault zone.
City Hall in ruins, 1906, from Larkin and Grove Street.
The earthquake lasted for less than a minute; however, the quake ignited several fires around the city, which burned for over three days. Even though the two disasters were linked, it was the fire, and not the earthquake itself, that devastated the city. The flames destroyed 490 city blocks and a total of 25,000 buildings.
Here’s an account from Jerome B. Clark, a businessman who lived in Berkeley but worked in San Francisco. On the day of the 1906 earthquake, he traveled to the city as usual, via ferry.
“Fires were blazing in all directions, and all of the finest and best of the office and business buildings were either burning or surrounded. They pumped water from the bay, but the fire was soon too far away from the waterfront to make efforts in this direction of much avail. The water mains had been broken by the earthquake, and so there was no supply for the fire engines and they were helpless. The only way out was to dynamite, and I saw some of the finest and most beautiful buildings in the city, new modern palaces, blown to atoms. First they blew up one or two buildings at a time. Finding that of no avail, they took half a block; that was no use; then they took a block; but in spite of them all the fire kept on spreading."
San Francisco waterfront after the 1906 earthquake.
The combined earthquake and fires killed an estimated 3,000 people and left more than 250,000 residents homeless in San Francisco. Damage estimates range from $350,000,000 to $500,000,000. In many ways, the city was destroyed. It would take many years for the city to recover and get back on its feet.
The 1906 San Francisco Earthquake remains one of the worst natural disasters in United States’ history.
What If The 1906 Earthquake Struck Today?
To get a sense of what a major earthquake, on the same scale as the 1906 quake, might look like in San Francisco today, we reached out to Laurie Johnson, an urban planner with over 25 years of experience in disaster-related consulting, and Patrick Otellini, the city’s Chief Resilience Officer.
According to Johnson, if an earthquake with the same magnitude as the 1906 quake struck San Francisco today, there are three main issues, besides the potential $34 billion dollar price tag, that are of concern to her.
Number one is having the same thing happen that occurred in 1906: a devastating earthquake followed by an even more devastating fire. “Given the high concentration of wood structures and vulnerability to both electric and gas related ignitions, a large-scale fire is a huge threat to the city,” said Johnson.
San Francisco in flames (1906).
A 2006 academic report, “When the Big One Strikes Again,” by Kircher et. al., says that a conflagration similar in scale to the 1906 fire is unlikely; the 1906 fire was responsible for over 80 percent of all losses. The report, however, does state that following a 1906-esque earthquake, several hundred individual fire ignitions will cause building damage and human deaths.
“We shouldn’t just be worried about the earthquake, we should be worried about the fire afterwards,” said Otellini, “especially looking at the fact that most water heaters, even though it has been required by code for a long time, often are not braced properly at home. That can be the single largest ignition source after a disaster. We not only need to think about what happens during the shaking,” he said, “but what happens the moment after the shaking stops and the fire starts.”
Ruins of the Armory destroyed by the 1906 earthquake and fire.
Johnson’s second concern is in regards to the city’s older concrete masonry buildings that are scattered throughout the city. Generally built prior to 1970, these buildings include many of the gorgeous, mid-rise structures in Pacific Heights, Nob Hill, and the Financial and Mission Districts.
Two firemen standing in front of a building destroyed in the October 17, 1989 Loma Prieta earthquake.
Otellini agreed. “Since 1906,” he said, “we haven’t experienced that kind of ground shaking in San Francisco at all. We can see building collapses of all types, but primarily those ones that we know are dangerous: soft-story buildings, certain concrete buildings, and older steel moment frame buildings. These are all hazardous occupancies that have been targeted under the earthquake safety implementation program for that reason: we don’t think they would survive that type of shaking.”
Fifty percent of the estimated deaths that would occur given an earthquake like 1906 striking San Francisco today would be caused by the collapse of unreinforced masonry buildings, older concrete buildings, and other structures that have not been strengthened, according to the Kircher paper.
“These are structures that are very vulnerable to collapse,” explained Johnson, “so we can have huge life loss in those structures depending on the time and day and how occupied they are. Some of them are places where people are living, some of them are places where people are working.”
San Francisco in ruins after the 1906 earthquake and fire, view from Rincon Hill.
The Kircher report estimates that there will be between 800 and 3,400 deaths as a result of building collapses across the region after an earthquake similar to the one in 1906. Human loss is expected to be greater if the earthquake happens during the day. The study also estimates that about 40 percent of San Francisco’s commercial buildings would sustain structural damage.
The city has made improvements to strengthen this aging infrastructure that predates many modern building codes. In 2013, a law was passed that requires soft-story buildings to undergo mandatory seismic retrofits by 2020.
“There’s been a tremendous amount of work that’s gone into upgrading our infrastructure and our building stock in the Bay Area,” said Johnson, “but a lot still needs to be done.”
The third issue that Johnson highlighted is the state of BART’s Transbay Tube. Opened in 1974, the tube is an underwater tunnel that carries four of BART’s transbay lines under the bay between San Francisco and Oakland.
A section of the Transbay Tube being lowered into San Francisco Bay. Photo courtesy of BART.
“There’s a vulnerability of the tube experiencing a failure that could cause catastrophic flooding,” said Johnson, “not to mention what would happen to any cars inside the tube at the time.”
According to the Kircher report, if an earthquake with the same magnitude as 1906 struck today, the Transbay Tube would be forced to close for two years, and would cost BART an estimated $860 million dollars to repair damages, undoubtedly wreaking havoc on our region’s public transit.
A seismic retrofit of the tube is in progress, and although the vulnerability of the Transbay Tube that Johnson mentioned is being addressed, the project won’t be completed for another few years.
We Know It’s Coming, So Be Prepared
“It’s not someone else, it’s us,” said Johnson. “People need to have a plan.”
To prepare for an earthquake, Otellini stressed having a communication plan. San Francisco has come a long way since Lotta’s Fountain, with technology like Twitter and texting, but according to Otellini, “a communication plan is the first step,” especially with family members, and with at least one out-of-state contact.
“Having a communication strategy with a person outside the region to be your point of contact for your family and friends is a bare minimum,” Johnson said. “Having food and water for 72 hours to me is another bare minimum. Thinking through your financials so that you have access to records and cash, I think these are the things that we need to think very carefully about in the Bay Area.”
S.F. Red Cross & Relief, No. 1, Relief Camp 8 - Lobos, July 28, 1907.
When the actual quake strikes, she said that “our instructions are to duck, cover, and hold. And not to run outside. Things can be falling off structures and wires can be breaking.” According to Johnson, even if you’re outside when the earthquake happens, you should try to get to a safe place and find protection.
In terms of when the earthquake, the “big one,” will strike San Francisco, no one can say for certain. “We have essentially something where stress has been accumulating over time. We’re getting closer and closer, we just don’t know because it’s geologic time and not human time.”
“We’re way overdue,” said Johnson. “When I started working in this field, the big earthquake was supposed to be in the next 30 years. There was a 70 percent chance of a major earthquake happening in the Bay Area, and we’re pretty close to the end of that 30 years.”
“I look at all the young people who’ve moved here to work in high tech and they think ‘Oh, that’s gonna happen in someone else’s lifetime,’” said Johnson. “That’s what I thought when I was their age 25 years ago — I thought I was infallible. It hasn’t happened yet, and if it didn’t happen in my time frame, and given the knowledge we have, it’s much more likely to happen in the next 30 years.”
“We know that the population of San Francisco is projected to be a million residents by 2040,” added Otellini. “No one disagrees with that. If we’re looking at systems that are stressed now, imagine how it’s going to be when we have an extra 150,000 people.”
“I think we have to take this as a real possibility and not just in our lifetimes,” said Johnson, “but in our near future — sooner rather than later.”
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