Chimney Sweep

Massive CA Earthquake Could Kill Hundreds; ‘It May Occur Tomorrow’

SAN FRANCISCO, CA — The “big one,” a powerful earthquake that could devastate California at any moment, will likely kill thousands of people and topple buildings, crumble bridges and roads, sever water lines and ignite numerous fires.

And “it could happen tomorrow,” earthquake engineering expert Keith Porter told USA Today.

“We don’t know when,” he told the newspaper. But “it will happen.”

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The US Geological Survey estimates that it’s far more likely than not that an earthquake measuring magnitude 6.7 will hit Los Angeles or the San Francisco Bay Area in the next 30 years: 60 percent and 72 percent, respectively.

The agency gives it about a coin-flip chance that the two regions will see an earthquake measuring magnitude 7.

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Experts are working hard now to mitigate the devastation of those disasters before they happen, especially since they know what to expect based on three devastating earthquakes that rocked the state in 1868, 1906 and 1989.

1868 Hayward Fault Earthquake

On Oct. 21, 1868, a powerful earthquake shook the fog-shrouded San Francisco Bay Area for more than 40 seconds.

The magnitude 6.8 earthquake happened on the Hayward Fault and was one of the most destructive in the state’s history, topping brick buildings, walls and chimneys in Oakland, San Francisco, Santa Rosa and San Jose. Napa and Hollister also saw serious damage.

Frightened people saw the ground move in waves and ran from homes. Cattle and fire engine horses panicked and bolted.

Shaking was felt as far away as Nevada. Aftershocks rattled the Bay Area for weeks after the initial jolt.

Even though the region was only sparsely populated — San Francisco had a population of just 150,000 at the time — about 30 people died in the quake. Even today, it ranks as one of the most destructive earthquakes in California history.

Towns in the East Bay sustained the most severe damage. Almost every building in Hayward, which had about 500 residents at the time, was destroyed or severely damaged.

San Leandro, with about 400 residents, saw many buildings destroyed. The second floor of the Alameda County Courthouse collapsed.

San Francisco Earthquake, 1906

On the morning of April 18, 1906, a massive earthquake shook San Francisco. The magnitude 7.8 quake, which lasted less than a minute, ignited several fires around the city that burned for three days.

Nearly 500 city blocks were destroyed.

“Despite a quick response from San Francisco’s large military population, the city was devastated,” according to The Center for Legislative Archives.

An estimated 3,000 people died in the earthquake and ensuing fires. About 400,000 people — around half the city’s residents — were left homeless.

Survivors faced weeks of difficulty and hardship, sleeping in tents in city parks and at the Presidio, standing in massive lines waiting for food, and cooking in the street to avoid setting off even more fires.

1989 Loma Prieta Earthquake

On Oct. 17, 1989, 83 years after the San Francisco quake, a 20-second tremor rumbled through the San Andreas fault, roughly 56 miles south of San Francisco and 10 miles northeast of Santa Cruz, near Mt. Loma Prieta in the Santa Cruz Mountains.

The Loma Prieta Earthquake killed 63 people and left more than 3,700 others hurt. More than 12,000 people were left homeless amid an estimated $10 billion in damage and economic interruption.

In all, more than 18,000 houses and 2,500 businesses were damaged. Another 963 homes and 147 businesses were destroyed.

“The most notable damage included the collapse of the elevated Cypress Structure section of Interstate 880 in Oakland, the collapse of a section of roadbed on the Bay Bridge, and extensive damage to downtown Santa Cruz and San Francisco’s Marina District,” according to the California Department of Conservation.

The Bay Bridge was unusable for a month. The World Series between the San Francisco Giants and Oakland A’s was postponed.

The magnitude 6.9 quake was felt as far away as San Diego and western Nevada, and was followed by several aftershocks, including a magnitude 5.2 aftershock that happened less than three minutes after the main earthquake.

In the week following Loma Prieta, 20 aftershocks of a magnitude 4.0 or greater were recorded.

The ‘Big One’ Is Coming

The Hayward Fault “will rupture violently again, and perhaps soon,” the geological survey warns. Studies showed that similar Hayward Fault quakes repeatedly jolted the region in the past, and the fault could be ready to generate another earthquake with a magnitude of 6.8 to 7.0.

A magnitude 7.5 earthquake on the Hayward Fault in the East Bay could result in $65 billion in damage, state conservation officials said.

“Revisiting the 1989 Loma Prieta earthquake serves as an important reminder to all residents of California that the geologic processes responsible for creating the beautiful natural landscape we enjoy can sometimes occur suddenly and violently, so it’s important to be prepared,” the state said.

And that’s just the Hayward Fault.

Residents in northern California, Washington, Oregon or British Columbia live in what’s known as the Cascadia subduction zone, where the geologic forces that helped shape the region remain active. Cascadia is known as a “region of earthquakes,” because of a massive, 700-mile fault that lies in wait just offshore.

The set of tectonic plates to the west is sliding beneath the North American Plate. Plate movements are irregular — and they aren’t smooth, according to a 2013 report by the Cascadia Region Earthquake Workgroup.

The plates are stuck, and stress builds until finally the fault suddenly breaks. It last happened 322 years ago, triggering a magnitude 9.0 earthquake, followed within minutes by a large tsunami.

“Stresses have now been building along the Cascadia subduction zone for more than 300 years, and the communities of Cascadia can be certain that another great quake will again shake the region,” the group said.

The quake would be akin to the massive tremor and tsunami that struck Japan in 2011. The Great Tohoku earthquake, as it became known, killed more than 15,000 people and destroyed or damaged more than 330,000 buildings. It left an estimated $199 billion in damage in its wake.

And in Southern California, the geological survey warned that big earthquakes on the San Andreas Fault are not only inevitable, they’re “extremely common” in geological terms.

In a report on so-called hypothetical “ShakeOut Scenarios,” the geological survey said the southern San Andreas Fault generates large earthquakes on average every 150 years.

The last earthquake similar to that of a hypothetical magnitude 7.8 earthquake on the southern tip of the fault happened more than 300 years ago.

Should such a quake happen again, the geological survey identified several major areas of loss. That includes older buildings that were built using outdated standards, damaged infrastructure — particularly to water systems — and ensuing business disruptions; and resulting fires.

And in San Diego, the local chapter of the Earthquake Engineering Research Institute found in a 2020 report that as many as 8,100 buildings are vulnerable to earthquakes.

A magnitude 6.9 earthquake could destroy 8,000 buildings and damage more than 100,000 others. An estimated 36,000 households would be left homeless, and the region could see $38 billion in building and infrastructure damage.

“Due to the location of the fault rupture zone, coastal communities may be cut off from nearly all lifeline utility and infrastructure services,” the report said. “Water, wastewater, and gas line services west of the fault rupture zone are estimated to be out for months.”

Furthermore, transportation lines along the Interstate 5 corridor could be severely impeded due to crumbling roads and bridges.

“We’re expecting a large fault rupture, almost six feet, a lot of liquefaction impacts, which basically is softening of the soil that causes a lot of impact to underground infrastructure like water distribution pipes,” Heidi Tremayne, executive director of the institute , told KPBS. “We’re worried that coastal communities could really be lacking some basic services for many months after an earthquake of this magnitude.”

Mitigating Disasters

Keith Porter, the earthquake engineering expert, told USA Today that areas affected by a major earthquake would see widespread cell service and power outages, water shortages, and massive fires.

Electricity could be gone for weeks. Thousands of people could become trapped in elevators, as first responders are busy helping elsewhere. This is particularly problematic at health care facilities such as hospitals, where stuck elevators could trap or prevent patients from changing floors, becoming a life-threatening scenario.

“That means people are dead in those elevators,” Porter said.

Survivors would need help from firefighters with special training and tools to escape.

Authorities have launched mitigation efforts, including by creating the Seismic Hazards Zoning Program to help with preparations and minimize death and property damage.

A year after the Loma Prieta earthquake, state lawmakers enacted legislation directing the California Geological Survey to map out areas most vulnerable to liquefaction, landslides and severe ground shaking.

Non-reinforced masonry, or “URM,” buildings are especially vulnerable to earthquakes, experts said, as they are inherently brittle and lack strength to withstand lengthwise stress as well as being pushed or pulled. The buildings are “prone to collapse even in earthquakes of moderate size,” the geological survey said.

Many non-ductile, reinforced-concrete moment-frame, or NDRC, buildings are also vulnerable. Experts recommend retrofitting “URM buildings” and many NDRC buildings using modern engineering techniques.

Additionally, hospitals and other facilities where disrupted service could threaten lives should consider implementing guidelines for restoring service after an earthquake, without inspection, experts recommend. Sensors should also be added to elevators so they stop and open doors at the nearest floor when strong shaking is detected.

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