Tsunami waves triggered by Pacific volcano eruption raise water levels in La Jolla

An undersea volcano that erupted in the South Pacific near Tonga produced tsunami waves that raised coastal water levels by 6 inches in La Jolla and 1.4 feet at San Diego Bay on Jan. 15, according to the National Weather Service.

The San Diego County Office of Emergency Services sent out an alert at 6:55 a.m. that the National Tsunami Warning Center had issued an advisory for the West Coast following the volcanic eruption roughly 5,300 miles southwest of San Diego. An advisory is less serious than a warning.

The weather service canceled the advisory in San Diego at 1:30 p.m. when it was apparent the surge here had played out.

The waves began arriving shortly before 8 a.m., roughly coinciding with a 6-foot-1-inch high tide. The extra water also showed up as surfers were trying to catch the tail of a west swell that had been pounding local beaches since midweek.

To many watching the beaches, the change in water level was not easily discernable.

“Even a foot change can be difficult for anyone to notice with the swell going on,” said Encinitas lifeguard Lt. John Strickland.

Lifeguards along the county coast restricted access to the water line but didn’t officially close beaches.

The county’s emergency operations team monitored the situation and was in communication with the local coastal jurisdictions, the weather service and the state.

“This was really weird; we usually associate this kind of thing more with earthquakes than underwater volcanoes,” said Brandt Maxwell, a forecaster at the National Weather Service office in Rancho Bernardo.

Tsunamis are rare in Southern California because the area is far from regions that produce the kind of underwater earthquakes and volcanos that generate such events.

But they do happen. A magnitude 8.8 earthquake that occurred off Chile in 2010 produced a small tsunami in San Diego Bay that damaged some docks.

— San Diego Union-Tribune staff writer Morgan Cook contributed to this report. ◆