Alaska aquiver: With 40,000 earthquakes a year, state to have its ground examined

Alaska averages 40,000 earthquakes per year,with more large quakes than the other 49 states combined, andAmerica's shakiest state is about to have its ground examined likenever before.

• RELATED |4.2 magnitude earthquake hits near Yukon, B.C. border
• RELATED |Several earthquakes hit central Alaska over the weekend

A federal agency that supports basic science research iscompleting installation in Alaska of an array of seismometers aspart of its quest to map the Earth's upper crust beneath NorthAmerica.

When the magnitude 9.2 Great Alaska Earthquake ripped through thestate in 1964, there were two seismometers in Alaska. At the end ofthis summer, there will be 260, swathing the state with instrumentsthat record seismic waves and give geologists a picture of the upper 80 kilometresof the Earth.

Alaska state seismologistMichael West calls it a "big freaking deal."

"This footprint of instrumentation rolled across the country andis now wrapping up this grand, 15-year project" in Alaska, Westsaid. The seismographs are deployed for the National ScienceFoundation by a consortium of U.S. universities that acquires anddistributes seismological data.

Engineering them for Alaska was a challenge.

A helicopter flies in a lightweight drill rig to dig into bedrockor permafrost for the seismograph, said Bob Busby, transportablearray manager for Incorporated Research Institutions for Seismology.

• Yukon, Alaska, northern B.C. rocked by quake, then another

• More than 100 aftershocks follow 6.2 quake that jolted Yukon, northwest B.C.

Like pieces of shell onhard-boiled egg

Solar panels mounted on fibreglass huts must gather energythroughout summer to charge lithium iron phosphate batteries equivalent to two or three batteries in a Prius that powerequipment through the long winter.

The array of seismometers, part of the science foundation'sEarthScope project, has the ambitious goal of explaining howcontinents formed as well as something of more immediateinterest: where dangerous earthquakes of the future may occur.

It's tied to the theory of plate tectonics, which holds thatEarth's rigid outer layer is broken into large, mobile plates, like
pieces of shell on a hard-boiled egg, if the shell pieces movedalong, over and under each other.

Tectonic plates average 80 kilometresthick and moveonly as fast as fingernails grow. But when they intersect, pressurebuilds until plates slip, causing earthquakes and volcanoes.

"Any kind of ground shift is somehow related to the tectonic plates," said Maggie Benoit, EarthScope science program director.

The study of plate tectonics is only about 40 years old, Benoitsaid, and the National Science Foundation made a
quarter-billion-dollar commitment to advance the field.

Alaska sees 11% of world's earthquakes

Alaska is especially active, with 11 per cent of the world's earthquakes every year, because it's located where two great plates converge, with the Pacific Plate slowly being pushed under the NorthAmerican Plate.

There are three big pieces to EarthScope. One is a borehole intothe San Andreas Fault to understand fault structure. A second is aseries of GPS stations that document plate movement.

The third part is USArray, the network of hundreds of portableseismographs. The array was placed first in western states and over a decade moved east to other states. In the Pacific Northwest, the data has contributed to imaging chambers of molten rock at Mount St. Helens.

Scientists in California are using GPS data to study groundwater use. A Brown University researcher is using data to
study the formation of North America in southern and eastern states.

Alaska is more than twice the size of Texas but has nearly 350,000 fewer people than Rhode Island. Earthquakes that would devastate cities elsewhere often go unnoticed in Alaska because they occur in the Aleutian Islands or other sparsely inhabited areas.

Data impacts building codes, tsunami prep

The 260 seismic stations in Alaska will be about 80kilometresapart. For added value, many are piggybacked with equipment to monitor weather and soil temperatures.

"That wasn't the original goal," West said. "But frankly, ifyou're going to go out and plop down a power system and real-time communications to some remote locations, you might as well hang a bunch of widgets off of it."

West said it's interesting to think about the evolution of theEarth over 100 million years, but his use of the data will be for less theoretical purposes.

Every public structure, he said, uses building codes created onhistorical earthquake data. The data helps set insurance rates anddesign tsunami evacuation zones for Alaska coastal communities.

Companies routinely make hundred-million-dollar design decisions formines, pipelines and ports based on knowledge of earthquake hazards.

"If they know what the hazard is, they can build to it," West said.