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The Big One What If The San Andreas Earthquake Hits California Tomorrow
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Mar 31, 2025
The "Big One" is an oft-used nickname for the big San Andreas earthquake that is predicted to hit California sometime in the near future. But while this earthquake will certainly be hugely destructive and very large, it won't be nearly as powerful as popular culture likes to portray it. That said, California will still need to buckle up because it's going to be a very bumpy ride.
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Underneath California lies one of the most infamous fault lines in the world
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the San Andreas Fault Line. Extending from the Gulf of California through Southern California and the San Francisco Bay Area
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and along the coast into Northern California, the San Andreas will, at some point, rip through California once more
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So what if the big California earthquake hits tomorrow? Today's episode is sponsored by Babbel, one of the top language learning apps in the world
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Hello, and welcome to What If Geography, where we try and answer the great geographic what-if
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questions of the world. I'm your host, Jeff Gibson, and today we're going to talk about
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one of the most researched, seismically active fault lines in the world. I am, of course
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talking about the San Andreas fault line. This is a fault line that will someday wreak havoc
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once again on the state of California. But before we get into today's episode
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consider following me on Twitter and Instagram to find more of my geographic content
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Links are in the description below. The San Andreas Fault is a continental fault line that extends roughly 750 miles through the state of California
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The fault is the dividing line between the Pacific Plate and the North American Plate
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But while it's all the same fault line, it is actually divided into three segments
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each with different characteristics and different earthquake risk. This is why specific areas in California are far more seismically active than others
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All that's to say, the fault line is quite unique amongst those in the world
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Luckily, the San Andreas Fault line also happens to be one of the most studied seismically active areas in the world
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The San Andreas Fault was first identified in 1895 by Professor Andrew Lawson of UC Berkeley Following the 1906 San Francisco earthquake Lawson concluded that the San Andreas Fault was not localized to the northern part of California
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but rather extended all the way into Southern California as well. This would be very important information
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for later on in the century. Speaking of the 1906 earthquake, this was really the first major earthquake
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of the industrialized world that struck near a major population center, and it absolutely destroyed the city of San Francisco
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However, because the earthquake preceded the Richter scale by a few decades
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we don't actually know how strong it was. Current estimates put the earthquake somewhere around a 7.7 to an 8.3 on the Richter scale
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Put this in perspective, a magnitude 6 earthquake will typically only last for a few seconds
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a magnitude 7 earthquake for about 15 seconds, a magnitude 8 earthquake for about 2 minutes
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and a magnitude 9 earthquake for at least 4 minutes. So this earthquake would have shook for somewhere around a minute and a half on the low end
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and over two minutes on the high end. But while the earthquake was absolutely devastating for San Francisco
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it would actually be the fires caused by the earthquake that would go on to destroy roughly 90% of the city
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When all was said and done, the 1906 earthquake is estimated to have caused roughly $8.86 billion in damage in 2020 dollars
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This was on top of the fact that over 3,000 people were left dead and a further 300,000 left homeless
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the San Andreas Fault Line would go on to wreak havoc on the state over the next 100 years
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Since the 1906 earthquake, over 60 major earthquakes of at least a 5.5 scale
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have struck the state of California causing some form of damage. This would include the 1989 earthquake that struck San Francisco
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which caused roughly $6 billion in damage, and the 1994 earthquake that struck Los Angeles that caused upwards of $40 billion in damage
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It's a relatively safe assumption that, about every other year, the San Andreas Fault Line will send a little shake up the spine of California
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wreaking havoc wherever it might hit. Sometimes that's near a major population center
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Sometimes it's not. Today, the San Andreas Fault Line continues to be a major source of concern for millions of Californians
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Not really knowing when or where it will hit gives off a certain amount of anxiety
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Luckily, California is perhaps more prepared than most areas of the world for a looming earthquake
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But before we dive into what a major earthquake in California would look like today, If you're enjoying this video, now would be a great time to subscribe
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More fun what-if geography videos are just a single click away. The Big One is an oft-used nickname for when the San Andreas Fault eventually erupts and
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splits California in half. That won actually happen for a number of reasons but it a popular concept that has been featured as part of multiple movies including a fairly recent movie called San Andreas starring Dwayne Johnson
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In this movie, a magnitude 9.1 earthquake strikes Los Angeles, splitting the earth open and causing unimaginable amounts of destruction for the city
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But while that is all very dramatic, the reality is much less so
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The San Andreas fault line will generate another big one sometime in the not-too-distant future
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It's an active fault line and there's no getting around that. So it's not a matter of if, but rather when and where
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But unlike popular culture, the big one will not split California in half
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In fact, the upper limit of the San Andreas Fault is put at a relatively low 8.2 magnitude
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which means that the big one will not be nearly as strong as the earthquake
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that will eventually wreck the Pacific Northwest, nor will it be as big as the Fukushima earthquake that rocked Japan in 2011
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But this doesn't mean it won't be incredibly destructive. If the big one was to strike tomorrow
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the amount of damage it causes would largely depend on where it hits specifically. And seismologists today are largely predicting
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that the next big earthquake will strike somewhere in the southern part of the fault line. This would largely include the Los Angeles
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and San Diego metro regions, but probably more likely to be the Inland Empire region
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San Bernardino and Riverside are expected to bear the brunt of the big one that's coming
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A US geological survey study predicted in 2008 that the next big earthquake
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that hits the Southern California region would likely result in around 1,800 deaths and over $200 billion in damages
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Determining the exact aftermath of a major earthquake is always going to be a huge challenge
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because there are so many variables at play. Recall the earthquake that hit San Francisco in 1906
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While the earthquake itself was very destructive, it was actually the fire that was started by the
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earthquake that did the most damage. Similarly, the 2011 earthquake in Fukushima absolutely wrecked
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that region of Japan, but it was the damage caused to a nearby nuclear power plant that caused far
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and away the most damage. However, thanks to that same 2008 study, we can at least make an educated
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guess at what California can expect. As mentioned already, there are really two causes of the damage
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the earthquake itself, and whatever might occur because of the earthquake. For the earthquake
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itself, the 2008 study is predicting that somewhere around 1,800 people will die and just about 213
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billion in damage will occur. This might sound like a lot, and truthfully it is, but it could
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actually be so much worse. Thanks to aggressive retrofitting undertaken by the state over the
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last few decades, the earthquake itself is expected to be relatively easy on key pieces of infrastructure
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such as lifeline highways bridges and buildings However one area of concern for Southern California is that the region is particularly vulnerable to large fires While the respective fire departments are well to tackle smaller or relatively isolated urban fires throughout the metro region an earthquake of this
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size could start hundreds of large fires everywhere. And given California's current dry and hot climate
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conditions and its proclivity for wood-framed buildings, the region is something of a tinderbox
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at the moment. Overall, a fire caused by the big one is expected to cause somewhere around $65
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billion in damage. And of course, there would also be huge business disruptions for the region and
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country at large. Recall back in 2021 when there was a huge bottleneck at the port of Los Angeles
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and Long Beach due to containers not being able to unload. Whenever the big one does hit the region
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it will grind all of this work to a halt and the ripple effect will be felt all over the country
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continent, and even the world. If you thought 2021 was bad for getting things delivered
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this will be far worse. The Cascadia subduction zone fault lies somewhere around 50 to 100 miles off the coast of the
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Pacific Northwest and runs about 620 miles from the northern part of California all the way
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through Oregon and Washington and ending off the coast of Vancouver Island, British Columbia
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And this fault will generate an earthquake far and way bigger than the San Andreas Fault
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In theory, the really big one could strike anywhere along this fault line
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However, scientists at the California Institute of Technology have calculated that the southern portion of the fault line is the most likely location of the next big earthquake
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This would place the likely epicenter somewhere off the coast of northern California up to about central Oregon
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And the implications for the San Andreas Fault are clear. It could trigger a chain of earthquakes down into California
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The Cascadia Subduction Zone Fault is expected to generate a magnitude 9.0 or more earthquake sometime in the next hundred years
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And when it does, there's a strong likelihood that the San Andreas Fault will erupt as well
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somewhere in the northern part of the state of California. This would very much include the Bay Area
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So while current models still predict the big one to hit somewhere in southern California
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given the Cascadia subduction zone, northern California is absolutely not safe. The San Andreas Fault Line will trigger another major earthquake
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However, determining when and where has been extremely tricky. Scientists have made multiple predictions over the years
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but none have really materialized as of yet. And each time a prediction comes and goes without occurring
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the public largely writes off what scientists might predict later. It's a very nasty feedback loop
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But again, it's not a matter of if, but when the San Andreas fault line
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decides to stir up some trouble. I hope you enjoyed today's episode on the big one
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If you did, please subscribe to my channel. And if you wanna watch more of my videos
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you can do so here. Thanks for watching. See you next time
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