Why one of the biggest earthquakes ever recorded caused so little damage

Los Angeles Times

2 days ago

SAN FRANCISCO — It was one of the largest earthquakes ever recorded, a magnitude 8.8 monster off the eastern coast of Russia.
Despite its remote location, the size of the quake immediately brought potential danger of tsunami to a significant swath of the globe, including Japan, Canada and the United States. Tsunami alerts immediately went out, covering millions of people, including the entire U.S. West Coast.
But for all its fury, the quake ended up not being a catastrophe. Dangerous waves that rose more than 10 feet never materialized outside of Russia, and even there, officials had no reports of deaths, and damage appeared to be limited.
'In this case, we mostly dodged a bullet,' said Mike Rademaker, harbormaster for the Crescent City Harbor, a place that saw deadly tsunamis both in 1964 with the Alaska mega-quake and 2011 when the great Japanese quake hit.
While those events represent worst-case scenarios, Tuesday's temblor represents a best-case scenario.
'With tsunamis, location and directionality is everything,' said Nathan Wood, a tsunami scientist with the U.S. Geological Survey.
The area near the epicenter off Siberia's Kamchatka Peninsula did see damage, but it was sparsely populated. Video of the town of Severo-Kurilsk, on an island just off the peninsula, showed a building being swept away.
But for areas farther out, initial modeling suggests the tsunami's energy was directed into the open Pacific Ocean, roughly between Alaska and Hawaii, and had time to weaken before it hit more populated areas.
'It just kind of shot right between the two of those [states],' Wood said.
The tsunami 'impacted the local community that was right next to the source [earthquake] where it happened,' Wood said. 'But for everyone else, it kind of just shot right down this empty hallway — in between the Aleutian Islands chain and the Hawaiian islands — and so there wasn't really a whole lot in its way.
'So by the time it got to the West Coast, like California, Oregon, a lot of the energy had been dissipated,' Wood said.
Russia saw tsunami waves as high as 16 feet, according to news wire reports, but tsunami heights maxed out at 4 feet in Crescent City, 3 feet in Arena Cove in Mendocino County, 2.7 feet at Port San Luis in San Luis Obispo County, 2.6 feet at Point Reyes in Marin County and 1.5 feet in Monterey. The totals were even smaller in Southern California.
The highest wave in the U.S. was 5.7 feet in Kahului, Hawaii, on Maui.
'It's a relatively good day,' state Sen. Mike McGuire, who represents a large swath of the Northern California coast, said Wednesday.
The extensive alerts issued after the earthquake struck at 4:25 p.m. Tuesday PDT sparked concern across the Pacific, as scientists raced to forecast how extensive the tsunami could be. A magnitude 8.8 quake ranks as the sixth most powerful earthquake on record in the past 125 years.
But by Tuesday evening, the National Tsunami Warning Center's forecasts indicated that Crescent City would see a tsunami that would likely cap out at no more than 5 feet, and with places like San Francisco and Los Angeles harbor at less than 1 foot or so.
Dave Snider, the tsunami warning coordinator at the National Tsunami Warning Center in Alaska, said it might be too early to assess how much damage this tsunami did, but 'it is true, maybe this one wasn't as bad as it could have been.'
'If the focus of this tsunami's energy is not pointed right at your coastline, the impacts to you could be pretty limited,' Snider said.
The magnitude of the earthquake is important, but it's 'more about how much of that water moved, and what direction was that energy pointed at the coastline,' Snider said. 'In this case, it looks like maybe it just wasn't focused at the California coastline with that intensity of other known events.'
There are other tsunami scenarios that pose far greater risks to California. One involves a near-shore tsunami, such as a magnitude 9 earthquake along the Cascadia subduction zone, just off the coast of California's North Coast, Oregon and Washington.
Depending on the strength and location of the quake, life-threatening waves could approach the coastline in as few as 10 minutes, perhaps not even enough time for an emergency alert to be issued, much less arrive on your cellphone.
Near-shore tsunami from other offshore earthquakes could result in waves of up to 6 feet above mean sea level at San Francisco's Ocean Beach; 8 feet in Long Beach and the Santa Monica Pier; 9 feet in Malibu and 30 feet on Catalina Island.
Another worst case scenario involves a major earthquake in Alaska, sending tsunami to California. Maximum projected distant-source tsunamis could bring waves of 15 feet above mean sea level to the Santa Monica Pier and Marina del Rey and 32 feet at San Francisco's Ocean Beach.
Awareness of tsunami alerts has improved over the years in large part to deep ocean pressure senors that can detect tsunami that are overseen by the National Oceanic and Atmospheric Administration, said Eric Geist, research geophysicist for the USGS.
'There were several, fortunately, in operation right off the Kamchatka subduction zone,' Geist said. 'So we knew, really quick, that a tsunami — and a fairly sizable one — was generated.'
One of the tragedies of the 2004 Indian Ocean tsunami was a lack of warning.
Helping matters is that the tsunami hit California when there was a lower tide.
The extensive warnings offered California officials another chance to handle a tsunami at a time when experts are urging both the public and government agencies to be more prepared.
In December, a tsunami warning from an earthquake about 30 miles from the Humboldt County coast prompted a decidedly uneven response across Northern California.
It was the first time the San Francisco Bay Area had ever received a warning of a 'near-shore' tsunami with little time to evacuate, and the response demonstrated how the public had little awareness of whether they lived or work in a tsunami hazard zone.
In the end, only a tiny tsunami, measured at 5 centimeters, was recorded in December.
Even Tuesday night, there were problems. The California Geological Survey recently updated its tsunami hazard map — showing places in California that are at risk of tsunami inundation. The state's website crashed, yet again — a repeat of the website failing during the December 2024 tsunami warning, although this time, media outlets, including The Times, made interactive versions available.
But other efforts at preparation against tsunami have borne fruit.
In Crescent City, officials noted that the one dock that structurally failed — 'H' dock — during Wednesday morning's tsunami actually worked as designed.
''H' dock was engineered as a wave-and-current attenuator with closely spaced pilings, which are specifically designed to disrupt and dissipate tsunami energy before it reaches the Inner Harbor,' Rademaker said. 'So its sacrificial role in the overall design appears to have functioned as intended, absorbing the brunt of the surge, and helping to protect the more interior docks.'
The Crescent City harbor was totally destroyed during the 2011 tsunami, and also suffered damage from a 2006 tsunami — events that each took a three-year rebuilding process. The statewide total in damage from the 2011 tsunami was estimated at more than $100 million. One person in 2011 died after being swept into the sea while taking pictures of the tsunami. The Crescent City tsunami in 2011 topped out at 8 feet.
The 1964 Alaska earthquake set off a catastrophic tsunami that devastated Crescent City, washing away 29 blocks and killing at least 11 people. Surges reached 21 feet above the average low tide.