Undersea eruption spurs tsunami alert
Humboldt County: Biggest flooding threat after eruption in Pacific ‘is over,' Eureka NWS says
Humboldt County residents awoke to a tsunami advisory alert Saturday morning following an undersea volcanic eruption near the Pacific island nation of Tonga in the early morning hours, which triggered high waves in the Pacific Ocean.
The advisory issued for Alaska, Hawaii and the West Coast of the United States, warned people to stay away from coastal waters and away from the shore. The National Weather Service’s Eureka office announced the advisory at 5:16 a.m. with then-predicted arrival times of 7:35 a.m. for Fort Bragg and 8 a.m. for Crescent City, with waves rolling in for an extended period.
As part of the advisory, Humboldt County issued phone alerts to residents.
Unlike a tsunami warning, which would call for immediate evacuations for people in lowlying areas due to flooding and dangerous currents, an advisory
recommends staying away from coastal waters and beaches.
Compared to the tsunami which originated in Japan and reached Crescent City in 2011, this tsunami is small. Deep sea sensors mark the volcano’s waves as being inches high, compared to the 2011 tidal wave which sensors at three feet in height. These waves increase in size as they approach the coast.
Humboldt State University geologist Lori Dengler monitored the event all morning long on Saturday. Speaking to the TimesStandard at around 10 a.m., waves continued to arrive on the North Coast’s shores.
“The highest water height so far in Crescent City is just over a foot and a half and that is arriving at high tide, so what it’s doing is adding another foot and a half of water on top of an already pretty high tide,” she said.
Dengler explained tsunami signals were still coming across the Pacific Ocean on deep water sensors, with surges predicted to continue to be picked up for an unpredictable period as the volcano continues to erupt.
Experts will continue to assess the situation to determine when the advisory will be lifted.
“We have to monitor the source, and as long as we’re seeing the source sending out tsunami energy, it’s not safe,” Dengler said. “When the water levels have dropped to a point, the National Tsunami Warning Warning Center will cancel that advisory. At that point, and based on what the county says, the tsunami threat will have passed.”
At around 12:35 p.m. the Twitter page for the NWS Medford office reported the maximum wave height observed in Crescent City up to that point in time to be 3.7 feet, or 1.12 meters.
NWS Eureka meteorologist Jonathan Garner pointed to the tsunami surge between one to three feet along with ocean conditions as a factor in strong currents in bays and harbors as well as effects on low lying areas.
“There will be some minor coastal flooding as well, although a high tide occurred (at about 9:15 a.m.), so the biggest coastal flooding threat is over,” he said.
Garner emphasized the risks of being too close to coastal waters even as the high tides had already passed.
“Stay off of those docks, those piers, the jetties and if you want to be safe stay away from the shoreline and definitely out of the water because of those swift moving currents,” he said.
Dengler pointed out recent geologic events are reminders for local residents that Humboldt County is prone to these threats.
“Back in December, we had an earthquake, which was a good time to remind you that we live in earthquake country. And today, we’re having a tsunami, which is a good time to remind you that we do have a tsunami threat. The most important thing you need to find out is if you live in a tsunami hazard zone, and you can find that out very easily by going online. The Redwood Coast Tsunami Work Group has a link to the California State tsunami hazard maps,” she said.
Folks who lack internet access or are not proficient with computers can call the Humboldt County Office of Emergency Services at 707268-2500 or the Eureka National Weather Service office at 707-443-6484 for more information on tsunami zones in the region.