MENDOCINO CO., 7/17/26 — On Friday, July 10, the ground under Round Valley wouldn’t stop moving. A run of quakes rolled through north of Covelo over a few-hour span — at least six of magnitude 2 or greater, topping out at magnitude 4.4 just after 6 p.m. and felt as far off as Ukiah, Willits and Fort Bragg. It did no real damage. It was the second time this summer a major fault under Mendocino County has slipped hard enough to be felt across the whole county.
The first was June 24, when the Maacama fault that runs under Willits produced a magnitude 5.6 near Tomki Road in upper Redwood Valley — the largest quake on that zone in about 75 years, enough to knock out power to roughly 8,000 customers and empty the county courthouse in Ukiah. Last week’s swarm was on a different fault, the Bartlett Springs, one of the least-studied fault systems in Northern California. Two of the county’s big inland faults, both talking, just over two weeks apart.
Mendocino County already knows what a larger one would do, because the county has run the numbers.
The county’s draft 2026 hazard mitigation plan — the document that sets out how it prepares for disasters — models a magnitude 7.4 earthquake on the Maacama-Garberville fault, the same system that slipped on June 24. Using FEMA’s Hazus loss-estimation software and a U.S. Geological Survey shaking map, and assuming the quake hits at 5 p.m., the plan puts the total direct economic loss at $1.07 billion.
A 7.4 is well within what the Maacama can produce; scientists put its ceiling somewhere north of magnitude 7, and consider the Bartlett Springs — the fault that swarmed last week — capable of a major quake of its own. A magnitude 7.0 isn’t hypothetical on the coast either. The county’s own plan notes that a magnitude 7.0 struck offshore near Cape Mendocino on Dec. 5, 2024, the strongest on the North Coast since the magnitude 7.2 Cape Mendocino quake of 1992.
What a billion dollars looks like on the ground
Most of the loss is where people live. The plan estimates $863 million in building-related damage, with 41% of it falling on homes and another 12% on interrupted business. Replacing utility systems — water, sewer, gas, power, phone — racks up about $162 million. Roads, bridges and other transportation take nearly $45 million. The quake would generate an estimated 83,000 tons of debris, the wreckage of buildings that topple.
The human toll in the model is smaller than the dollar figure but not zero. At 5 p.m., the plan estimates, a 7.4 on the Maacama would displace 41 households, send 25 people to public shelter, injure 39 badly enough to need medical care — nine of them hospitalized, four with injuries the plan says could turn life-threatening without prompt treatment — and kill one person.
Lifelines would hold better than the property. The county expects its essential services to be at 88% function within a week and fully restored within 30 days. That’s the optimistic half of the model.
Why the Maacama is the worst quake for these towns
The plan models a second scenario — a magnitude 7.8 on the northern San Andreas, a larger earthquake by every measure. It comes out to $263.7 million, less than a quarter of the Maacama’s bill.
The reason is geography. The San Andreas runs offshore and west, away from where people live. The Maacama runs straight under them — through Ukiah, Willits, Hopland, the Highway 101 spine. A smaller quake on the closer fault does far more damage than a bigger one farther away. For Mendocino County, the Maacama is not the second-worst fault. It is the one that matters most.
The buildings the plan singles out
The plan reserves its plainest language for one kind of structure: unreinforced masonry — brick and block buildings put up before modern seismic codes, without the steel that lets a wall flex instead of fall. They are, the plan says, “highly vulnerable to cracking, partial destruction, or even total collapse.” To make the point, the county’s own document includes a photograph of a warning sign posted inside a Ukiah restaurant, telling customers the building is unreinforced and may not be safe in a quake.
Those signs exist because state law requires them. They are the version of an earthquake warning the county has now: a notice on the wall, and a plan on the shelf that already carries the number.
The city of Ukiah has never taken a full count more recent than a 2014 inventory, which found about 50 unreinforced masonry buildings — the type most likely to fail in a strong quake. “We haven’t had any buildings retrofitted since that time,” said Shannon Riley, the city’s deputy city manager.
The public’s window to weigh in on the plan has already closed. The county posted the draft for comment on April 6 and took comments through April 20. It has not adopted the plan yet, and there’s nothing on the council agenda.
The faults gave their own comments — on June 24, and again on July 10.
“The city of Ukiah has never taken a full count more recent than a 2014 inventory, which found about 50 unreinforced masonry buildings — the type most likely to fail in a strong quake. “We haven’t had any buildings retrofitted since that time,” said Shannon Riley, the city’s deputy city manager. ” – Any updates on the Palace hotel? Is this building getting steel reinforcement?
Models likely provide mapping of potential threats. Where can I find the maps?
I’m just a yahoo on the internet, but this analysis strikes me as wildly optimistic. Would love to know more about what went into the scenario and how it was evaluated, because I can’t help recalling the unpleasant surprises Ukiah got when unknown gas lines were discovered during street work, and the fact that so much quake damage is often from fires in their wake. And I’m happy to shift my worry over to the Maacama fault, but wasn’t 1906 pretty damaging to this area? Very interesting piece, but it raised a lot of questions along with concern that the county seems to be just hoping for the best and letting this slide.