Two recent earthquakes in the San Francisco Bay Area highlight the region’s precarious position of experiencing one of the deadliest and costliest natural disasters in recent American history.
On Saturday, April 6th, around 11:15 a.m., a 3.4-magnitude tremor struck around 7 miles deep near Garber Park on the Berkeley-Oakland border. That earthquake was felt across the SF Bay Area, with anecdotal reports of buildings in downtown SF swaying, albeit ever so slightly, and houses shaking as far down as San Jose; no immediate injuries or structural damages have been reported.
Two days later, another sizable earthquake — a 3.2-magnitude tremor — shook the ground about two miles away from The Geysers, the world’s largest geothermal field located in the Mayacamas Mountains of California, roughly 72 miles north of San Francisco. That earthquake, too, produced light trembling, capable of being felt tens of miles away from its epicenter; weak shakes were felt as far down as Windsor and Santa Rosa.
Several smaller, far less detectable — detectable here connoting the ability to be felt by us bipedal apes, sans equipment — quakes occurred in and around these epicenters. These all happened just days after several tremors rattled parts of Northern California, a magnitude of 4.4, shook the area around Chico.
What do both these objectively large earthquakes have in common? They occurred along connected fault lines where “The Big One” is expected to transpire next.
Those geological breaks? The Rodgers Creek Fault and the Hayward Fault.
Up until 2015, it wasn’t all too clear if these fault lines, which exist in near parallel to one another — the Hayward Fault dipping below the San Pablo Bay; the Rodgers Creek Fault running through Sonoma County, begging off (or in) the San Pablo Bay — were connected. That all changed in 2016 when geologists discovered the two lines were connected with the ends of the two faults linked between Point Pinole and Lower Tubbs Island. Moreover: The same study showed the Hayward Fault is a component of the much larger Calaveras Fault, the latter fault benign branch of the San Andreas Fault System.
As a result, geologists have labeled the two connected fault lines the “most dangerous” geological break in North America; their relation to one another means these two fault lines, now referred to as the Rodgers-Hayward Fault system, could collectively produce a quake as strong as 7.2 magnitudes; it’s also hypothesized that any major seismic event on either fault has the potential to involve movement on the other, compounding the risk of “slipping” and additional seismic activity.
Per Earth, An earthquake of the aforenoted strength in this part of the country would prove catastrophic — in more ways than one.
The loss of human life could number in the hundreds, if not thousands, leaving tens of thousands more injured; over 100,000 businesses sit within the Rodger-Hayward Fault system, and such a tremor could cost billions in lost productivity, and Meta, Apple, and Google’s headquarters all sit within shaking distance of a Rodgers Creek-Hayward-epicenter earthquake; billions of dollars in structural damages would occur — 1989’s Loma Prieta caused $6.8 billion in related damages; (for context, the theory lay 7.2-magnitude earthquake yet to strike the Rodgers-Hawyard Fault System would be priority three-times stronger than the 6.9-magnitude Loma Prieta tremor, according to the USG’s “How Much Bigger…?” Calculator); the tunnels operated and managed by the Bay Area Rapid Transit (BART) that run underneath the San Francisco Bay would likely experience surfer extreme damages… which could take years to repair.
It’s a catastrophe that seems imminent.
A study conducted by the UC Berkeley Seismology lab concluded that the Hayward Fault has a 31.7% chance of rupturing in a 6.7 magnitude earthquake or greater before 2036. And given what you know about its relationship to the Rodgers Creek Fault line, it’s a predicted tremor that could be amplified and across a larger swath of the Bay Area
The intentional catastrophizing that are narratives around “we’re overdue for ‘The Big One’” are often slandered. They’re based on fear-mongering (and in the day and age of the internet, built around clickbait hooks) and fail to offer the pragmatism needed to head this threat with level-headedness.
You’ve got the facts. You know the outcomes. Go and make sure those emergency earthquake kits are well stocked (or… well… made).
Feature image: Courtesy of USGS
