Earthquakes and tsunamis dominated social media in Southeast Alaska Saturday evening, but the resulting tidal surges thankfully were nonexistent or very small.
A tsunami warning for much of the West Coast turned into an opportunity for emergency drills in southern Southeast Alaska, with no observed surge in Ketchikan and slight waves on Prince of Wales Island and other outer coastal communities.
On Saturday evening, a magnitude 7.7 earthquake hit Haida Gwaii, also called the Queen Charlotte Islands, south of Ketchikan off the coast of British Columbia.
Shortly after the temblor hit, tsunami warnings began. One alert predicted a 2-1/2 foot surge in Ketchikan harbors, and warned residents to avoid the waterfront.
The alert later was downgraded for the entire West Coast and Hawaii, with a warning only of potential “non-damaging” sea-level changes for some communities.
There was a surge of about four inches in Craig, according to City Planner Brian Templin. While the actual wave was small, the city made sure everyone was ready for a much larger event.
“Police officers began going door-to-door in the low-lying coastal areas that were most vulnerable, advising people that they should move to higher ground,” he said. “We opened the pool and elementary school on one side of Craig, and the recreation center and city gym on the other side of Craig as points that people could evacuate to.”
People in the Craig harbor also were asked to evacuate or take their boats out to deep water. Templin said emergency equipment also was moved to high ground on both sides of Craig. After the first tsunami wave hit at about 9:10 p.m., the emergency response team sent observers to the shore.
“The police officer that went and observed saw the water run out a little ways and come back in,” he said. “His observations matched pretty much what the tidal gauge here in Craig showed, … which was about a third of a foot run-up above the normal tide level.”
Templin said the community was ready. Officials came up with a response plan about a month before last year’s earthquake and tsunami in Japan. They modeled their evacuation plan on the tsunami from Alaska’s 1964 Good Friday earthquake.
“So we actually talked through all of these issues, not only how we would respond, but how we would make some of the decisions about evacuation, where we would choose to position emergency equipment,” he said. “Craig is a series of islands connected by causeways, so there’s high points on east and west Craig, but the harbor is between the two, so in a large event, transportation would be difficult back and forth.”
Saturday’s tsunami warning was a good test of Craig’s plan.
“It went very well,” he said. “I think that was the big part of it. Having talked it through before, having practiced it before, that we showed up and really everybody did exactly what we talked about, exactly what we practiced. It worked out very well.”
Jim Baichtal, a U.S. Forest Service geologist in Thorne Bay, said the primary fault that affects Southeast Alaska is the Queen Charlotte Fault, which runs up the side of Haida Gwaii, and along the outer coast of Southeast to Yakutat.
“The Pacific side of the plate is moving northward at about 2 inches a year. Somewhere along that,” he said. “So it builds up stress and strain on some places in this fault and every once in a while it ruptures.”
Baichtal said that since 1898, which is as far back as records go, there have been 322 ruptures, or earthquakes, along that fault, or about three per year. Of those, 34 have been greater than a magnitude 6.
“The most notable earthquake that recently affected Southeast Alaska would have been on Aug. 22, 1949, which was an 8.1 on that same fracture system, just to the very northern tip of Haida Gwaii, or the Queen Charlotte Islands,” he said. “It’s the largest earthquake that’s occurred in British Columbia, historically. And it was felt in Craig and Ketchikan and all the way down to Seattle.”
That quake caused significant damage in Craig, and a cannery sank on its pilings. More recently, in June of 2004, a magnitude 6.8 earthquake occurred on the Queen Charlotte fault.
Baichtal said frequent smaller quakes are better, because they’re letting off some of the pressure.
”But, we will have and continue to have occasionally large earthquakes associated with the movement of that Queen Charlotte fault,” he said.
There reportedly was little damage from Saturday’s quake, even at its epicenter. Some Ketchikan residents reported feeling the quake and its aftershocks, others noticed nothing.
Coast Alaska member stations reported little or no effect from the earthquake in other Southeast communities. In Sitka, authorities didn’t evacuate anyone, but encouraged harbor residents to head upland for a while; in Juneau, some people reported that their hanging light fixtures swung a little during the quake; and in Haines, boat owners were asked to tighten their mooring lines.
No Alaska communities experienced surges of more than 6 inches. In British Columbia, the surges were closer to a foot; and parts of Hawaii experienced waves of about two feet.
Unfortunately, for many people hoping to find up-to-the-minute information, the West Coast and Alaska Tsunami Warning Center’s website was intermittently down for about two hours Saturday evening.
According to the center, there was a “configuration problem with the web-caching company.” That problem has since been fixed.
The center suggests that if the site is down again in the future, people try an alternative site, www.tsunami.gov.