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Get ready

turnagain

Anchorage’s Turnagain Heights neighborhood after the Good Friday earthquake of 1964/Alaska Seismic Hazards Safety Commission photo

Geophysicists from the Universities of Colorado and Montana are warning that 2018 could be a rockin’ and rollin’ year for major earthquakes due to a slowing of the Earth’s rotation, and Alaska is past due for a big shake.

 

“Since 1900, Alaska has had an average of one ‘great’ earthquake (magnitude 8 or larger) every 13 years,” according to the Alaska Seismic Hazards Commission. The last 8.0 or larger quake in the 49th state came in 1986.

Alaskans were lucky in that the 1986 shake was centered off the Andreanof Islands in the Aleutian Island chain more than 1,000 miles west-southwest of the state’s urban core.

“The quake, which caused a tsunami, popularly known as a tidal wave, damaged buildings at Adak Naval Air Station. Walls cracked, and windows shattered,”  the Los Angeles Time reported. “But the 5,000 residents of Adak Island, most of them part of the Navy contingent, already had been evacuated to higher ground when the wave hit.”

Tsunami warnings were issued for the U.S. West Coast and Hawaii, but no serious damage was reported.

Sixteen years later, the 2002 Denali Earthquake rattled not only Alaska, but the entire North American continent. A 7.9 tremblor, it didn’t quite rise to the  8.0 standard, but it cracked the Richardson Highway in Eastern Alaska, and rattled the TransAlaska Pipeline System (TAPS) that generally parallels the highway for 368 miles south from Fairbanks to the Port of Valdez.

 

denali quake

Overdue

It has now been more than 15 years from that November shake, and the planet is entering a year in which University of Colorado scientist  Roger Bilham and University of Montana geophysicist Rebecca Bendick have suggested more earthquakes than normal are to be expected due to a slight change in the speed at which the earth spins.

“On five occasions in the past century a 25 to 30 percent increase in annual numbers of greater than magnitude 7 earthquakes has coincided with a slowing in the mean rotation velocity of the Earth,” according to the abstract of a report they presented to the annual meeting of  The Geological Society of America in Seattle back in October. 

The Seattle presentation of a model to predict periods of increased seismic activity caused a small media tremor.

“Huge uptick in earthquakes predicted in 2018, as geologists note Earth’s rotation is slowing,” a Fox News headline screamed in late November, but the warning was quickly forget when North Korea launched what was believed to be an intercontinental ballistic missile (ICBM).

Which is a greater threat to Alaska – another big earthquake or a Korean ICBM – is impossible to say, but North Korean leader Kim Jong Un is at the moment making nice and claiming his aggressive pursuit of nuclear weapons and long-range missiles was only a matter of self-defense.

Jong Un is unpredictable, but earthquakes are even more so. The U.S. Geological Survey is blunt about this.

“No,” it answers. “Neither the USGS nor any other scientists have ever predicted a major earthquake. We do not know how, and we do not expect to know how any time in the foreseeable future.”

Bilham and Bendick, however, say there is strong evidence for suggesting an increase in the likelihood of earthquakes based on the speed at which the earth spins. And as a simple statistical matter, Alaska is overdue.

Good news

The good news, at least for Alaskans, is that the Bilham-Bendick examination of the past indicates the place where the greatest change in earthquake activity is likely to take place is near the Equator where the force of the spinning earth is greatest.

Bilham and Bendick aren’t sure why a millisecond shift in speed of the spinning planet influences earthquake activity, but they have theorized it might be related to a slight shift in the gravitational pull between the planet’s mantel and its core.

“The striking thing we’ve noticed is that the deceleration of the Earth is five years ahead of the earthquakes,” Bilham told Newsweek last year. “If it were the other way around, it would be boring.”

We are this year at the point of the five-year lag from the last slow down.

The Bilham-Bendick theory might seem a little bit out there, but a fair number of other scientists seem to think it has validity.

“I’ve worked on earthquakes triggered by seasonal variation, melting snow. His correlation is much better than what I’m used to seeing,” Michael Manga, a geophysicist at the University of California, Berkeley, told Science Magazine. 

The bad news for Alaskans is that what happens at the equator might not stay at the equator.

There’s a lovely debate in the scientific community about whether major earthquakes are somehow linked. Quakes appeared to ripple around the globe in 2014, but a later study by the USGS concluded the unusually large number of big quakes that year remained within the range of random possibilities.

“Basically, we can’t prove that what we saw during the first part of 2014, as well as since 2010, isn’t simply a similar thing to getting six tails in a row,” USGS research geophysicist Tom Parsons told LiveScience. “(But) it’s possible that global-level communications happen so infrequently that we haven’t seen enough to find it among the larger, rarer events.”

Scientists have previously found linkage between smaller quakes.

blurb

Get ready

No matter that no one knows when exactly the next big Alaska earthquake will come, what is known is that one will come.

The Pacific and North American tectonic plates collide beneath the Aleutian Trench just off Alaska’s southern coast. As the Pacific plate pushes beneath the North American, it reduces the pressure of the earth’s mantle pushing down on the planet’s superheated core, melting some of core rock and sparking a push upward as the molten lava that sometimes flows from the string of volcanoes that stretches from the Aleutians Island to the Aleutian Range peaks clearly visible across Cook Inlet from downtown Anchorage.

“In the Gulf of Alaska region, the subduction of the Yakutat plateau complicates the area, and is responsible for mountain building in the Chugach-St. Elias Ranges and the Alaska Range,” adds the Incorporated Research Institutions for Seismology of the National Science Foundation.

The IRIS website has a nice video illustrating how this all works to set Alaska to shaking, an inevitability for which all Alaskans should be prepared but too many aren’t.

Are you? What would you do if Anchorage was without gas or electricity for a matter of days?

Is there extra food in the house? Water?

“I think of the Good Friday quake yet with 85 percent of the state’s  food coming on three barges weekly into the port of Anchorage,” emailed Art Nash, a University of Fairbanks Extension Service authority disaster preparedness. “I’ve thought even a decent tsunami from here to Seattle could really be a problem.”

Nash stressed that Alaskans need to be prepared for natural disasters. While the Federal Emergency Management Agency (FEMA) advises residents of the Lower 48 they should always keep on hand provisions to survive at least a three-day disaster, the agency boosts that recommendation to seven days in Alaska. 

“Simple stuff,” Nash said, “making sure the gasoline in the generator isn’t stale, having grill propane cylinders full,  having a wood burning back-up for heat/cooking/thermoelectric abilities, having a short hose for the bottom of the hot water heater if the well pump doesn’t power on, etc… ”

All of those things, he said, “can go a very long way whether it is a disaster or just power lines down” from the sort of mega-snowstorm that hit the Copper River valley late last year.

UAF provides a whole lot of emergency preparedness information here. An emergency supply checklist is here.

It makes sense to be ready because it’s not a matter of if Alaska will get hit with another big earthquake; it’s just a matter of when.

The state is already overdue.

 

 

 

 

 

 

 

 

 

 

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