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Sudden 6.5 earthquake in long-quiet Alaska region sets off alarms

Jennifer GibbinsThe Cordova Times

CORDOVA -- A 6.5 magnitude earthquake rolled through the neighborhood earlier this week. The quake took place at 10:42 a.m. on Monday, 165 miles south of Cape Yakataga in the Gulf of Alaska. While one or two locals felt a little shake, rattle and roll, the event went mostly unnoticed -- except at the West Coast and Alaska Tsunami Warning Center in Palmer, Alaska.

"Oh yeah, the alarms were going off," said Cindi Preller, tsunami program manager at the center. "The seismometers are live, real-time feeds. The first alarm that goes off is a voice alarm. Then a beeping alarm. We knew within two minutes the location and magnitude."

Because of the quake's location, more than 150 miles offshore, a tsunami was not expected and no watch, warning or advisory was issued by the center. However, this quake definitely caught the attention of geologists and emergency management specialists.

"This was a big quake, 6.5, and it took place on the edge of the Yakatat Block. The last time we have seen any significant activity in this area was in the 1980s," said Preller. "The northeast area of the Pacific Ocean has been a little quiet and ideally we'd like to see more activity in the range of 3-4 magnitude. This event definitely perked our ears up."

Coincidentally, Preller and a team of 18 geologists, emergency management specialists and local responders from state and federal agencies and nine communities had just been in Cordova the prior week for a Tsunami Operations Workshop. But more about that later.

Yakatat Block perks up

Earthquakes happen constantly around the world, and particularly across Alaska. Hop onto the USGS website on any given day and there is a good chance you will see multiple events taking place across Alaska. The number of earthquakes annually in Alaska far exceeds California’s total. On Tuesday of this week, six of the first 12 events listed were all in Alaska, and five of those were in the vicinity of the now not-so-quiet Yakatat Block.

The Yakatat Block, is an area of the earth's crust along southcentral coast of Alaska. It converges with the Pacific plate along its southern edge, with the Fairweather Fault to the north and the Aleutian Megathrust to the west. Looking at a map of earthquakes in Alaska, it is clear that, as Preller says, the Yakatat Block has been quiet back to 1987. What especially concerns Preller and others is that after such a long period of inactivity, there is a lot of built up pressure and the likelihood is greater that there will be a significant quake with the potential to generate a tsunami -- similar to what happened in 1964.

The 9.2-magnitude great Alaska earthquake of 1964 is still the second highest recorded earthquake anywhere on the planet. Of the 132 deaths associated with the event, 122 were attributed to the Pacific-wide tsunami it generated. Peller says it is not a question of "if", but when and knowing what to expect is the key to recovery preparedness.

Small-wave myth

"There are the big myths," said Preller. "That a tsunami is a giant wall of water, that there is only one wave, that it is something you can surf -- or that it simply won't happen."

Peller's laptop is loaded with an almost-kaleidoscopic array of hundreds of colorful charts, diagrams, maps and videos. Ask her any question and she immediately starts tapping on the keyboard, opening up images to illustrate her point.

The great wall of water is perhaps one of the most important myths for the team to debunk.

"For Cordova and other Alaska coastal communities, the more likely scenario is a wave in the neighborhood of one meter," said Peller. "And that is a very destructive wave. It is really important for everyone to understand the severity of the small wave."

Preller spins her laptop around and plays a video of the 2011 tsunami in the Santa Cruz Yacht Harbor, 14 hours after the Japan earthquake. In the video it is a sunny day, police are patrolling the waterfront asking the public to move away from the harbor area, but the public is not heeding the request. Instead, people can been seen walking along the docks, lined along the shoreline with cameras and packed shoulder to shoulder along an elevated walkway waiting for the tsunami like the next big act at SeaWorld.

At first the docks start to roll gently, but in an instant the water silently charges through the harbor with speed and force, tossing boats up on docks and snapping floats into pieces as the crowd ooo's and ahh's. In this instance, the height of the wave never rises above the bank, but the destruction is evident. One very lucky man manages to ride out the wave standing on a dock surrounded by boats ripped from their slips. The speed and force of the wave's exit is impressive, too.

This leads to the second myth: there is only one wave, and the third myth, that you should hop in your boat and ride it out.

"There were reflections from the Japan earthquake across the Pacific Ocean for seven days," said Peller. "There is a lot of energy behind a tsunami."

Indeed. Tsunami waves can travel across the open ocean at speeds well over 600 mph, as fast as a jet flies. Speed is influenced by the depth of the ocean. But the potential threat from a wave is higher as it reaches shore. In an area enclosed by land, such as Prince William Sound, the energy can reflect, reverberating and sloshing waves around as if confined in a bath tub.

Tsunami ready?

During the recent workshop emergency personnel and city staff from Port Graham, Seward, Homer, Yakutat, Seldovia, Valdez, the Kenai Peninsula Borough and Cordova participated in table-top exercises, drilling on how information is received, evacuation procedures, sheltering, medical services and more.

"Training and exercises help develop consistent understanding and language between local, state and federal operations," said Preller. "Who issues a warning? How is that information received? What does it mean? What is your plan?"

"Harbor staff are not typically included as emergency responders, but in the event of a tsunami, the big player is the harbor."

The town of Cordova is considered a Tsunami Ready Community, with a designated evacuation plan and personnel trained in recovery preparedness. A weekly siren that goes off at noon can be heard all over town on Wednesdays telling the community that in a real emergency, they will be directed to safety. Additional sirens are in the plan for outlying neighborhoods and signs have been ordered telling people to move to higher ground in the event of a tsunami, designating Cordova’s Mt. Eccles Elementary School as the evacuation destination.

Preller and her counterparts in Homeland Security and other agencies also urge citizens to become educated. Part of the team's time in Cordova included visits to local schools to teach students the science behind earthquakes and tsunamis and to train kids in what to do. In the 2004 tsunami in Thailand, the lives of some 100 tourists were saved by a 10-year old girl from England who warned them to flee to safety moments before the tsunami engulfed the beach. The girl recognized the signs after learning about tsunamis in her geography class.

Preller advises people to prepare personal emergency kits and to plan to be able to self sufficient for seven days.

Jennifer Gibbins is editor of The Cordova Times. Reach her at editor@thecordovatimes.com. Used with permission.