Earthscope Array helps seismic researchers across Alaska

Twenty-five thousand earthquakes occur in Alaska each year, ranging from little shakers to large, damaging jolts.

So in response, some say, "Deploy the Earthscope Transportable Array!" – it sounds like a line from a science fiction series or movie. In reality, it is the newest line of research equipment helping to detect earthquakes, volcanic eruptions and weather in some of the most rugged stretches of the state.

Recently, the Campbell Creek Science Center's

series hosted speakers involved in the U.S. Array project. The audience was able to learn about the challenging weather and mosquito-infested installation sites, while enjoying a nice fireplace.

This past summer, the last of 193 seismic stations, or huts, were installed in Alaska, making it a part of 280 instruments that cover Alaska and northwest Canada – the last link in a grid that covers the Lower 48, as well. The project started in 2004.

According to Bob Woodward, director of Instrumentation Services for Incorporated Research (ISIR) Institutions for Seismology, "The project here, in Alaska, has been the last several years of a 15-year project."

He says it's a $40-million endeavor, with each hut, or enclosure, holding the seismic sensors and batteries, along with a lightweight drilling system that is sometimes trucked or flown, but mostly delivered by helicopter.

Max Enders, station deployment coordinator for IRIS, gets the equipment into places where sometimes no one has been before. Helicopters are a main mode of transportation for the hut.

"That hooks up to a helicopter sling, and all of it goes out to the station in one helicopter load," Enders explains. "We unpack it, put the sensor in the ground and by the time we get it there – since we've done all the preparation beforehand – it's basically running the minute we get the system in."

A lightweight drilling system was key to transport to the sites and get a good hole to safely ensconce the sensors in the ground. Whereas, older sensors sit on concrete pads.

Woodward says by putting the sensor down in this bore hole, it makes the sensor much quieter and lets the research scientists see the signals better.

These new instruments can also detect infra-sound, or atmospheric acoustics, like a thunderstorm passing by and volcanic eruption. And this data came in handy, when one station went down without warning. The instrument allowed scientist to see some seismic rumblings, like heavy footsteps. When Ryan Bierma, a field operations manager, was dispatched to the site for repairs and a look around, he knew what had happened right away.

"The bear had just really gotten upset for some reason, and he yanked all the cables out," Bierma said.

But bears and setbacks aside, the main focus of this multi-year project is to study seismology and map the earth's crust.

Robert Busby, transportable array manager for IRIS, says it will allow researchers to get a better handle on which faults are active, and how they move.

"That gives us a better idea of how plate tectonics work," he adds.

The Alaska Earthquake Information Center and National Weather Service benefit from this new data stream, too. One-hundred and thirty-two of these installations provide temperature, pressure, wind speed and direction observations.

Bierma says the information will be invaluable.

Think of all the air charter and air traffic – all the villages are relying on good weather data and forecasts," he says.

IRIS Seismologist Kasey Aderhold says the next two years will be a steep learning curve, because the new array is feeding in so much information, and it is free to the public.

"We're going to see some really interesting stuff. What's down there, what other things can we detect?" says Aderhold. "It's just going to be really exciting."

Woodward adds, "Already, the data are contributing to improved weather forecasts and improved seismic understanding in Alaska."

The U.S. Transportable Array is expected to be dismantled in 2019, unless the state or other interested agencies can purchase some of the instruments. But until then, research will continue.

IRIS is a coalition of 114 universities and institutions, and it is sponsored by the National Science Foundation.