Now, we're getting a clearer picture of what that impact will look like, thanks to a team of seismologists and mathematicians working with a powerful supercomputer at the Lawrence Livermore National Lab.
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"Hundreds of thousands of individual computer chips that are working together to solve one problem," said geophysicist Arthur Rodgers.
In this case, the problem is one that could face the Bay Area any day now: a magnitude 7 earthquake on the Hayward Fault.
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"An earthquake like this happened in 1868, but only 3,000 people lived in the East Bay. Now, we've got 2.5 million," Rodgers said.
Along with the people came, houses, freeways, and water mains -- like the big pipe that recently burst in Hayward, in a failure that's been attributed to fault creep.
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"Our water and electricity and gas and our transportation corridors have to cross many major faults," Rodgers said.
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That's where the new simulation comes in. Rodgers showed it to us on a giant monitor at the lab.
"The earthquake starts in the north part near Richmond, and travels to the south. The colors show the intensity of the ground shaking," he explained.
Though it's not a real earthquake, the most detailed computer simulation ever made of a magnitude 7 quake in the East Bay is based on real measurements.
'We look at small earthquakes like the magnitude 4 earthquake that happened in Berkeley last month," Rodgers said.
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The simulation shows more clearly than ever one of the peculiarities of the East Bay's geology. When it comes to shaking, the area around the Hayward Fault is, in a sense, backward: the hills shake more than the flatlands.
"These rocks have been dragged along the Hayward Fault for millions of years," explained, gesturing to at the topographical shading on the simulation map. "And they've been scrunched up and compressed and thickened."
In other words, he said, the hills east of the fault are made of soft rock that could shake much more violently than the flat ground west of the fault. The simulated quake runs for 20 seconds, but in Livermore, it shows the ground shaking for a minute and a half. Rodgers says that's because it's a "sedimentary basin" where soft material has accumulated on top of the bedrock.
Of course, the greatest damage is still likely to be closest to where the fault ruptures, Rodgers said, especially when buildings aren't made to withstand it -- something downtown Napa experienced firsthand during the South Napa Earthquake. Rodgers says more detailed simulations could help engineers design more resilient structures in the future.
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