Quake research to map Earth’s crust

ANCHORAGE, Alaska — Alaska averages 40,000 earthquakes per year, with more large quakes than the rest of the U.S. combined, and America’s shakiest state is about to have its ground examined like never before.

A federal agency that supports basic science research is completing installation in Alaska of an array of seismometers as part of its quest to map the Earth’s upper crust beneath North America.

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

The seismographs are deployed for the National Science Foundation by a consortium of U.S. universities that acquires and distributes seismological data.

The array of seismometers, part of the science foundation’s EarthScope project, has the ambitious goal of explaining how continents formed as well as something of more immediate interest: where dangerous earthquakes of the future might occur.

It’s tied to the theory of plate tectonics, which holds that Earth’s rigid outer layer is broken into large, mobile plates, like pieces of shell on a hardboiled egg, if the shell pieces moved along, over and under each other.

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 North American Plate.

Earthquakes that would devastate cities elsewhere often go unnoticed in Alaska because they occur in sparsely inhabited areas.