Russia quake triggered 19-hour tsunami advisory; local surge fizzled

Last week’s 8.8 earthquake in Russia initially triggered a tsunami watch on the West Coast, indicating a tsunami was possible and to be prepared. That was later elevated to a tsunami advisory, which means a tsunami is expected to strike and could cause dangerous currents and waves, potentially flooding beaches and harbors. People are advised to keep their distance. (via NOAA)

The Tiburon Peninsula was under a tsunami alert for nearly 19 hours last week after an 8.8-magnitude earthquake off Russia’s coast triggered the strongest global tsunami-alert system activation in more than a decade.

No local evacuations were ordered, and no injuries or damage was reported.

The National Oceanic and Atmospheric Administration’s National Tsunami Warning Center in Palmer, Alaska, first issued a tsunami watch July 29, the lowest-level alert, for the U.S. West Coast shortly after the quake struck at 4:25 p.m. Pacific. That was upgraded to an advisory at 6:30 p.m., with the initial surge predicted to hit San Francisco at 12:40 a.m. July 30.

“Stay away from the water! Stay away from beaches and waterways! Remain away from shore until local officials say that it is OK to return,” the National Weather Service Bay Area warned on social media.

Those warnings are standard under a second-tier tsunami advisory, which is issued when the surge is expected to produce strong currents and waves capable of flooding beaches and harbor areas but without widespread coastal inundation. A tsunami warning — like the one briefly issued on the Tiburon Peninsula after December’s 7.0-magnitude quake off Humboldt County — is more severe, signaling a dangerous surge likely to cause major flooding and prompting evacuation of at-risk zones.

By Ark estimates, roughly 1,000 homes, businesses and public facilities sit in Tiburon’s and Belvedere’s combined tsunami inundation zones as mapped by the California Geological Survey, though that’s for an extreme event — a 9.3 Alaskan quake that would send a 13-foot wall of water to the peninsula.

When the tsunami arrived in San Francisco Bay at 1:12 a.m. July 30, initial surges were less than one foot atop normal tides and storm surges. Within hours, the bay experienced tidal swings of 2 to 5 feet within 15-minute periods, creating dangerous currents, according to the weather service.

While tsunami wave heights may seem modest, they travel at jet-plane speeds across deep ocean waters before slowing to 20-30 mph near shore, creating rapidly rising surges that appear as fast-moving floods rather than breaking waves.

Point Reyes recorded the highest tidal deviation in Marin, nearly 2 feet at 4 a.m., more than three hours after the initial surge arrived, the weather service reported. The regional alert was canceled about 11 a.m. July 30, though water levels continued to fluctuate and strong currents remained possible for several days, the weather service said.

“The ocean remains dynamic and dangerous,” it said, warning beachgoers to check with lifeguards before entering the water.

The Pacific alert was canceled about 7:20 a.m. July 31.

Local response and communication

No evacuations were ordered in Marin or for the Tiburon Peninsula, and as with the December alert, local public officials were silent throughout the event, with no use of the Tiburon Talk or Belvedere Breeze newsletters, press releases or other means to contact residents about the advisory or direct them to AlertMarin or the county’s Public Emergency Portal for updates.

“It did get upgraded to an advisory, but it never got to a warning level,” joint disaster coordinator Laurie Nilsen of the Tiburon Police Department said. “The city managers, police chief, fire chief and other staff were all monitoring and communicating during this time.”

While local officials have said they rely on AlertMarin — the county service that sends alerts by phone, text, email or smartphone app — just 35% of adults in Tiburon and 38% in Belvedere are signed up for the system as of June 30, according to data provided by Marin Director of Emergency Management Steven Torrence.

The combined 34% for the 94920 ZIP is on par with the county’s overall 33% sign-up rate for adults, but it leaves a large majority unconnected to the primary alert system.

Further, for those who are signed up, AlertMarin partially failed amid December’s tsunami warning, with notifications reaching some residents more than an hour after being triggered but just minutes before the surge was predicted to hit Marin’s northern coastal areas. During that hour, however, state and county officials were learning the warning was about to be called off, and the surge never materialized locally.

Last week, Torrence said, the Office of Emergency Management posted the upgraded advisory to the county’s Public Emergency Portal website at 6:30 p.m. July 29, then initiated text alerts through AlertMarin at 8:30 p.m.

For Ark staff, those arrived within about 20 minutes. About the same time, neighboring jurisdictions including the Sausalito and Mill Valley police departments issued separate alerts to their residents, repeating the warning issued by AlertMarin: “There is a tsunami advisory in effect for Marin County’s ocean and bay coastlines. Avoid coastal areas, beaches and waterways. No evacuations are advised at this time. Strong currents are expected to arrive around 12:40 a.m. Updates and tsunami inundation map visit: emergency.marincounty.gov.”

“Timing and message type differed based on this event being a ‘distant source’ tsunami versus the December event being a possible ‘near source’ tsunami,” Torrence said, noting the two-hour delay between the upgraded alert level and the AlertMarin notification was strategic to allow coordination, monitoring and validation with the National Tsunami Warning Center, California Office of Emergency Services and other regional partners regarding wave heights and threats.

The National Weather Service, which issued wireless emergency alerts in December, determined those weren’t necessary this time, Torrence said. He said AlertMarin also has wireless emergency alert capability, where all cellphones connected to towers in the alert area vibrate, play a loud tone and display an emergency message — with no need for sign-ups or special apps. Recent upgrades also allow the county to directly activate the Tiburon and Southern Marin fire protection district emergency sirens when necessary.

“These functions are the fastest, loudest and most far-reaching methods for alerting, and they will be used in the event of a significant threat to the community,” he said.

After the December quake, Tiburon Peninsula public-safety officials said an examination of local communications, including with media outlets, would be part of a post-incident review and potential integration into emergency-response plans, but it’s unclear whether any protocol changes were made.

Global impact and earthquake details

The Russia quake struck on a mega­thrust fault about 80 miles southeast of its far-eastern Kamchatka Peninsula, where waves reached 10-13 feet in some areas, though the Kremlin reported no casualties.

It tied for the sixth strongest earthquake ever recorded and the most powerful since the 9.0 magnitude earthquake that devastated Japan in 2011.

The area is a seismic hot spot that was rattled by five powerful earthquakes earlier in July, the largest measuring 7.4 magnitude. The region sits on the Pacific Ring of Fire, an area of intense seismic and volcanic activity.

The 8.8 quake triggered tsunami alerts across one-quarter of the Earth, affecting coastlines from Russia to Chile. Hawaii was placed under a tsunami warning, with residents evacuating coastal areas as waves reached more than 5½ feet.

Nearly 2 million people in Japan were under evacuation advisories as waves up to 10 feet struck its Pacific coast. Chile elevated its warning to the highest level for most of its Pacific coast and evacuated five prisons in low-lying areas.

The hardest-hit area on the U.S. West Coast was Crescent City in Northern California, where tsunami waves reached 4 feet on top of a 4-foot high tide, creating combined wave heights of 8 feet. The city activated tsunami sirens and evacuated low-lying areas late July 29. Initial damage estimates of $100,000 were later revised to about $1 million, but no injuries were reported.

Crescent City has a long history of tsunami damage due to its geography. In 1964, a tsunami killed 11 people and destroyed 289 buildings in the city.

On the Tiburon Peninsula, the last tsunami to cause damage was in January 2022, when local seas swelled 3 feet following the eruption of an underwater volcano in Tonga. The surge caused a floating dock and gangway to break free in Richardson Bay at The Cove at Tiburon apartments, temporarily stranding a resident who was rescued by good Samaritan boaters.

Public-safety reporter Tyler Callister contributed to this report. Reach Executive Editor Kevin Hessel at 415-435-2652.