It lurks ominously beneath California’s many natural wonders, a reminder that nothing in this landscape is truly permanent.

It’s been described as “the mother of all earthquake faults,” the source of both our geological birth and, perhaps, our ultimate undoing.

But the most unnerving thing about the San Andreas fault these days may be its silence. It’s a mystery scientists are still trying to unlock.

The San Andreas is central to any discussion of California. It’s the massive 800-mile spine of the state, trundling up the Coachella Valley to the San Gabriel Mountains, and pushing along the edge of Silicon Valley to beyond the Golden Gate.

There is no simple answer for why California’s longest fault, responsible for some of America’s most powerful earthquakes, has produced so few in the last century.

But it is clear that the quiet period is only increasing strain on the San Andreas, as well as on the state’s second-longest fault, the San Jacinto.

A new study underscores the concern. Researchers estimated that key sections of the fault in Southern California are at their highest level of tectonic strain in the last 1,000 years.

The San Andreas, in other words, is locked, loaded and inevitable.

Ticking tectonics

There are generations of Californians who have never experienced the fury of the San Andreas.

The fault was responsible for a megaquake that ripped through the then-sparsely populated state in 1857 — an event that, if repeated today, would reap mass destruction.

In 1906, “a crack in the edge of the world,” as author Simon Winchester described it, flattened San Francisco.

Modern Californians have been forced to make do with Hollywood’s CGI versions of the fault, which cast it as one of our state’s darkest villains.

But sooner or later, scientists say, California’s earthquake faults will rupture in a way not seen in the modern era. While California has seen sizable temblors since the great San Francisco quake of 1906, the state’s faults are capable of producing intense shaking over a much larger area than seen during more modern events such as the Sylmar, Loma Prieta or Northridge quakes.

“We keep accumulating that earthquake energy, and it has to be released. And the only way it gets released is through large earthquakes,” said U.S. Geological Survey geologist Kate Scharer, one of the new study’s co-authors. “The small ones don’t really do it.”

A section of the California Aqueduct crisscrosses the San Andreas fault dozens of times.

Advertisement

• Share via Close extra sharing options

Advertisement

The latest study, published last month in the Journal of Geophysical Research: Solid Earth, set out to create a model that calculated the seismic strain on three key segments of the San Andreas and San Jacinto faults where they intersect at the Cajon Pass in San Bernardino County.

The model is based on a number of factors: the estimated timing of earthquakes on the faults over a record of the last 1,000 years; satellite observations of how fast tectonic plates are moving; and estimates of how rigid Earth’s crust is, which determines how much stress can be accommodated and then released, Scharer said.

The computer model “found that tectonic stress has now reached higher levels than at any point in that entire record. From the model, we see that the conditions that historically preceded large joint ruptures crossing both fault systems are now approaching,” said Liliane Burkhard, the lead author of the study and a scientist at the University of Bern in Switzerland and the Hawaii Institute of Geophysics and Planetology at the University of Hawaii.

The last major temblor to strike urban Southern California, the magnitude 6.7 Northridge earthquake of 1994, resulted in severe damage and the deaths of about 60 people. But it was also mostly limited to a relatively small area of Los Angeles County.

By comparison, a hypothetical magnitude 7.8 earthquake on the southern San Andreas would simultaneously bring violent shaking to L.A., Orange, Riverside, San Bernardino, Ventura and Imperial counties and could result in 1,800 deaths, according to a U.S. Geological Survey estimate published in 2008.

The findings of the latest study don’t change the overall expectation of a big earthquake hitting Southern California. But they underscore the persistent risk — as well as the possible scale of the disaster.

There’s a 60% chance of a magnitude 6.7 or greater earthquake striking the Los Angeles region by 2045, according to USGS estimates published in 2015. There’s about a 1 in 5 chance of such a quake striking on the San Andreas fault within L.A. County and the Inland Empire.

Why the drought?

The decades-long relative earthquake drought “is an unusually long interseismic period, and stress has been accumulating continuously throughout,” Burkhard said.

The authors created a 28-second animation, showing how tectonic strain increased along the faults over the last 1,000 years. Big earthquakes then release that strain, before the cycle starts again.

This animation condenses 1,000 years of the Cajon Pass’s earthquake history into 28 seconds. Tectonic stress, shown in shades of orange and red, builds up along three fault segments. Following an earthquake, that stress is released. (Liliane Burkhard / University of Bern / University of Hawai’i at Manoa)

Advertisement

The study calculated that the San Andreas fault just northwest of the Cajon Pass and the San Jacinto fault just southeast of the pass are at their highest tectonic strain since the year 1100.

The pass, located roughly 50 miles northeast of downtown Los Angeles, marks the dividing line between the San Gabriel Mountains to the west and the San Bernardino Mountains to the east.

Specifically, the study’s authors calculated that the current tectonic stress was 2.8 megapascals on the San Andreas northwest of the pass, surpassing the previous highs of 2.7 just before big quakes in 1469 and 1691.

For the San Jacinto, the authors calculated a current seismic stress of 3.6 megapascals, surpassing the previous high of 2.9 before an earthquake in the year 1249.

The study noted that it has been an unusually long time since a megaquakes has hit Southern California. The San Andreas fault northwest of the Cajon Pass usually has big quakes every 100 to 150 years, Scharer said, though intervals of about 200 years are not unheard of.

On the San Andreas southeast of the pass, big quakes usually happen every 200 to 250 years. But the most recent quake on the San Andreas along the Salton Sea, close to the Mexican border, was about 300 years ago.

There are some limitations to the study’s model, scientists acknowledge. For instance, the model presumes that when large earthquakes hit, all the tectonic stress that had been accumulated in the fault gets released, “so you start at a ground state of zero and then you accumulate back up until you have that next big event,” Scharer said.

But whether all that stress actually gets released during a big quake is not definitively known.

The Mormon Rocks in Phelan, Calif.

Tectonic risks

Whenever it strikes, a supersized earthquake on the southern San Andreas would be like no earthquake seen in living memory in California.

The 1857 quake, estimated to be a magnitude 7.9, produced 63 times more shaking energy than the 1994 Northridge earthquake, and across a much larger swath of the state.

In 1994, “violent shaking,” or Level 9 on the Modified Mercalli Intensity Scale, causing great damage in substantial buildings, affected only part of the San Fernando Valley.

But a magnitude 7.8 San Andreas quake hypothesized by the USGS in its 2008 ShakeOut scenario would cause that kind of shaking across Southern California.

In 1994, emergency responders from across Southern California were able to focus the bulk of their efforts on especially hard-hit areas. That wouldn’t be possible in a regionwide disaster.

It might be tempting for Californians to tune out talk of the “Big One” after hearing about it for most of their lives. But generational catastrophes do strike — be they an earthquake in San Francisco in 1906, a hurricane in New Orleans in 2005 or tsunamis in the Indian Ocean in 2004 or Japan in 2011.

Tectonic rewards

Earthquakes are part of the bargain of living in California, a product of the same forces that allow people to ski and surf on the same day. The same tectonics that drive earthquakes act as the state’s landscape artists, said Julian Lozos, associate professor of geological sciences at Cal State Northridge.

“Because we are on the edge of the continent, we’re on a plate boundary, and have been a plate boundary for a couple hundred million years. There’s constantly been stuff crashing into North America, and getting stuck to it, and getting uplifted, and erupted through, and slid around,” Lozos said.

The Sierra Nevada, California’s mightiest mountain range, “are the guts of the volcanoes that used to be there when there was a subduction zone … and then when those volcanoes stopped erupting, the guts of them lifted up through the crust,” Lozos said.

Big Pines Highway rises out of a valley to ride a ridge created by the tectonic forces of the San Andreas fault, two miles southeast of the unincorporated Mojave Desert community of Valyermo, home to about 450 residents.

The same forces that produce earthquakes are also what led gold to form in the Sierra foothills, inciting the state’s famous rush.

Tectonic movement also created today’s Central Valley, a highly productive agricultural area that was once part of the ocean, then an inland sea, and then a freshwater lake, Lozos said.

“Everything about what we see here is stuff that formed because of that plate boundary then, and it’s getting moved around by the plate boundary now,” Lozos said. “And so if we didn’t have anything like that, we would be Nebraska.”

But the risks, like the rewards, are significant. The San Andreas runs right through cities in the Inland Empire. The Los Angeles Basin is also at risk.

If an earthquake on the San Andreas comes from the south and heads north, it would shuttle all that shaking energy “right into downtown,” Lozos said, causing shaking that could last two to three minutes.

“Geologically, L.A. is a bowl of Jell-O. It is a hard rock bowl full of really soft, squishy stuff that shakes very easily,” Lozos said.

It is business as usual at the Wrightwood Inn on a recent Tuesday night. According to a recent study, seismic pressure has been gradually building in the area for more than a century.

It’s not certain why it’s been so quiet between earthquakes, said Scharer. Another study, published in 2023, suggested the lack of sudden, major floodwaters funneling into Lake Cahuilla, the larger historical predecessor to the Salton Sea, may have something to do with it.

Scharer said the study’s results are a good reminder to prepare for the next big earthquake.

To be sure, the computer model’s results are not a prediction, and all models have their limitations and uncertainties. Still, its suggestion that the fault systems are “more loaded than at any point in the 1,000-year record,” Burkhard said, “is a finding worth taking seriously.”

“In the end, the most important message is a simple one: Let’s make sure we are prepared,” she said.

Three-quarters of Colorado residents said they were worried about whether they would be able to afford to continue living in the state, according to a poll conducted this spring.

Last year, about 70% of people responding to the Colorado Health Foundation’s annual Pulse poll said they weren’t sure living here would remain financially feasible. That rose to 76% this year.

“That majority concern was cutting across regions, across income levels, across racial and ethnic groups,” said Lucia Del Puppo, senior vice president at FM3 Research, which works with Democrats.

The poll found that the majority of those sampled said they had already cut back on entertainment spending and charitable giving, with smaller shares saying they’d skipped meals, delayed medical or dental care, or paid a utility bill late.

Only about one in four people said they hadn’t changed their spending or dealt with a financial setback in the last year, with older people and Republicans reporting less budget strain.

“It’s significant and it affects the overall economy” when people reduce their discretionary spending, said Lori Weigel, principal of New Bridge Strategy, which works with Republicans.

The responses suggested a significant minority expected further financial strains in the coming year:

• About two in five worried they or a family member would lose health insurance
• Three in 10 worried about affording enough food
• One-third thought they might lose their housing because they couldn’t afford their mortgage or rent

Notably, more than half of renters were worried about whether they could continue to afford their housing, Weigel said. One-third said they’d avoided asking their landlords to fix problems to avoid rent increases, and one-quarter said they’d taken on high-interest debt, such as payday loans or credit card balances, to deal with housing costs, she said.

Lower-income people and those who identified as Black, Hispanic or Native American reported greater financial struggles than other groups.

Even people who haven’t had to cut back are worried about affordability. When asked to rate the seriousness of a list of potential problems, 85% said both the general cost of living and the cost of housing were either “very serious” or “extremely serious.” Additionally, 82% said the cost of health care was a very serious or extremely serious problem.

Younger people were particularly worried about housing costs, with 94% of millennials and 90% of Generation Z members describing the problem as very or extremely serious.

At the same time, when respondents got the chance to name the most important issue facing the state, the largest share — 28% — chose government and politics. The cost of living and inflation came close behind, with 25% deeming it the top issue.

It’s been a deadly summer on Hawaii roadways so far.

Since Memorial Day on May 25, there have been at least a dozen fatalities, accounting for roughly 25% of the total, which stood at 48 as of Friday. At the same time last year, the number was at 69.

The period between Memorial Day and Labor Day is known nationally as the “100 Deadliest Days” for teen drivers. Due to inexperience, speed, distractions and drunken driving, experts says summer is when teens are 20% more likely to be involved in a fatal crash than the rest of the year, and Hawaii is no exception.

“While it’s encouraging to see fatalities lower than this time last year, every life lost on Hawaii’s roads is one too many,” said Makena Young, MADD Hawaii program director, in a statement. “The recent deaths of these young people are heartbreaking reminders that summer is an especially dangerous time to be on our roads.”

She added, “At MADD Hawaii, our mission is to end impaired driving, but we also know that safe driving requires responsible choices behind the wheel every time. Whether it’s speeding, distraction, impairment, or simply taking unnecessary risks, those decisions can have lifelong consequences for families and entire communities.”

Hawaii residents are still reeling from the death of a 16-year-old, identified as Kalena Abelmann of Hawaii Kai, who died after her car flew off of the Pali Highway last month.

Honolulu police said at about 6 a.m. on June 18, the teen was driving Kailua-bound on the Pali at a high rate of speed when she lost control after the tunnels, went airborne, and dropped about 50 feet into a ravine.

Firefighters found her in the brush below, and she was pronounced dead at the scene.

In June, another teen died in a fiery crash on Daniel K. Inouye Highway, also known as Saddle Road. Hawaii island police identified the teen as Mackenzie Valentin, 17, of Hilo.

On June 4, police said Valentin was driving a Toyota 4Runner westbound on the highway when she lost control at a curve near mile marker 18. The car hydroplaned into the oncoming lane and collided with a Ford F-450 truck, then caught fire, with her trapped inside.

Valentin was taken to Hilo Benioff Medical Center, where she later died.

The Hawaii Department of Transportation afterwards declared a traffic emergency zone between mile posts 5.5 and 28 on the highway. Police said they would step up enforcement along the stretch, as it was the fifth fatality there.

Fatalities of every age

Hawaii’s traffic fatalities included a broad age range – from a 1-year-old boy hit by a car in a cul-de-sac in Hawaii Kai to a 93-year-old man who crashed after driving the wrong way up an H-1 freeway off-ramp.

At the start of the year, two tragedies involved elderly citizens struck by cars in marked crosswalks.

Stella T. Nakamura, 93, of Honolulu, died on Feb. 11 after being struck outside of Kuakini Medical Center in Liliha.

Just before 7 a.m., a motorist turning left from a driveway onto North Kuakini Street struck Nakamura, a retired registered nurse at Kuakini. She was in a marked crosswalk with a walk signal.

About two weeks later, King Leung Lau, 82, of Honolulu, was hit by a large SUV while in a marked crosswalk on Alexander Street in Punahou. Firefighters extricated her from beneath the vehicle, where she was pinned. She later died at a hospital.

The Kuakini neighborhood has had other pedestrian fatalities, including in 2012, when 88-year-old Martha Miura of Nuuanu was hit by a sedan while crossing Kuakini.

Donda Spiker, spokesperson for Kuakini Medical Center, said driver and pedestrian safety is a 24/7 concern, and that the center sends internal messages to staff about driving and walking carefully to and from campus.

“Kuakini Street has become a busy street due to the numerous health and medical facilities and schools in the neighborhood,” said Spiker in an email. “Although Kuakini Health System is on private property, many drivers drive through our property as a shortcut to get to and from School Street or Kuakini Street and the freeway onramp/off ramp.”

In 2023, the center requested an additional sign from the city at the corner of Kuakini and its Waikiki Service Road to remind drivers to stop before turning right onto the campus.

But the Honolulu Department of Transportation Services at the time informed her additional signs were not possible due to height and number limitations.

Taking action

After a record-setting high of 128 traffic fatalities last year, the state and police have doubled down on efforts to bring down those numbers.

The state Legislature this year passed bills updating the traffic codes on e-bikes, approving the use of technology to stop speeding, and installing pedestrian safety improvements near schools.

The “stop super speeders” bill, or Senate Bill 2023, allows courts to require anti-speeding technology for drivers convicted of excessive speeding and drag racing.

DOT, which supported the bill, said approximately one-third of all traffic fatalities in the state in recent years have involved speeding-related factors.

Senate Bill 3234 — introduced in honor of road victim 19-year-old Tehya Mahelona — appropriates $2 million toward pedestrian safety improvements near school properties. Mahelona died in October while walking to her early morning job in Nanakuli due to a chain-reaction crash caused by speeding.

The improvements would include all-way crosswalks, similar to the one in Waikiki, raised intersections, or both.

Key bills that would have helped protect vulnerable pedestrians and bicyclists, however, did not pass.

The goal of Senate Bill 2470, or the “pedestrian head start bill,” was to help prevent these types of tragedies, according to Malia Boksanski, transportation equity policy analyst at Hawaii Appleseed.

It would have authorized DOT to install two low-cost tools — leading pedestrian intervals and accessible pedestrian signals — at certain intersections.

These tools are recommended by the Federal Highway Administration and have proven effective in other states, according to Boksanski.

The leading pedestrian intervals give pedestrians a head start of 3 to 7 seconds before drivers get a green light. It makes pedestrians more visible to turning vehicles and helps those who are slower to start.

The FHWA recommends the use of LPIs for intersections with high-turning vehicle volumes and for an aging population.

The accessible pedestrian signals communicate “walk” and “don’t walk” signals through audible and vibrotactile cues, making them accessible to blind and low-vision pedestrians.

The Hawaii Association of the Blind supported the bill, saying its members have encountered very dangerous intersections despite traffic signals.

Hawaii Appleseed will advocate for the bill again next year.

Another Senate bill that did not pass would set up a task force to examine Finland’s tiered traffic fines system, which charges higher fines from those with higher incomes

The Honolulu Police Department, which in April launched a “Safer Roads Together” initiative, is now carrying out a ”Summer Safety Surge” with public service announcements and stepped-up enforcement of speeding and other violations in targeted areas across Oahu.

HPD in June reminded drivers that many recent crashes shared common, preventable factors, such as speeding, failure to yield – and impaired, distracted, and reckless driving.

“While traffic fatalities are down compared with this time last year, progress does not mean complacency,” said acting Deputy Chief Brandon Nakasato in the release. “Every decision behind the wheel matters, and by slowing down, eliminating distractions, and making responsible choices, we can help protect ourselves, our loved ones, and the most vulnerable members of our community.”

The number of pedestrian fatalities has dropped to 11 so far this year compared to 24 at the same time last year.

There have so far been no bicycle fatalities in the state this year, compared to five at the same time last year. There have, however, been collisions involving bicyclists that resulted in critical injuries.

The number of fatalities involving vehicle collisions was the exception, having increased to 27 this year compared to 20 at the same time last year.

The latest fatality occurred on the Fourth of July, when a woman, identified by the Medical Examiner as Savalivali Vivao, 28, of Honolulu, crashed into a concrete barrier on the H-1 freeway.

Police said Vivao was heading westbound when she crossed several lanes of traffic and for unknown reasons crashed into the barrier. She was pronounced dead at the scene.