Transportable Array Station 457A in Florida: first such seismic station on the U.S. East Coast. Credit: IRIS |
Yulee, Florida. Not a place one usually thinks of as an Earthquake Epicenter.
But this swampland not far from the Georgia state line is now home to a state-of-the-art seismic station known as 457A.
Here,
within a few miles of the Atlantic Ocean, 457A has been installed to
record ground motion from earthquakes. Earthquakes do happen on the East
Coast of the United States, as the Virginia quake of August, 2011
attests.
The
new seismic station is part of EarthScope, a project funded by the
National Science Foundation (NSF). It’s one of some 400 stations
collectively called the Transportable Array.
The
array has—one-by-one—slowly been making its way across the country in a
wave of instrumentation. Transportable Array Station 457A is the first
such station to reach the East Coast.
On
the West Coast in 2004, the array started its eastward migration. As it
moved, it transmitted information from more than 1,350 locations across
the United States.
By
the end of 2013, the array’s East Coast stations will occupy 400 sites
from Florida in the south to Michigan and Maine in the north, including
sites in the southernmost regions of Ontario and Quebec, Canada.
Researchers placed the stations in a grid approximately 70 km, or some 43 miles, apart each operates for about two years.
Data
recorded by the seismometers help scientists develop a better
understanding of the geologic structure inside the North American
continent.
“Scientists
can use these data to generate 3-D images of Earth’s interior that are
very similar to CT scans in medicine,” says Greg Anderson, NSF program
director for EarthScope. “The images show Earth’s structure from the
core to the surface in never-before-seen detail.”
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“With
the installation of 457A,” says Anderson, “the Transportable Array has
stations active on all four coasts of the ‘lower 48’: Pacific, Atlantic,
Great Lakes and Gulf of Mexico.”
Each
station is self-contained, using solar panels to recharge the batteries
that provide power to the seismometer and other sensors and electronic
systems. The entire instrument is placed in a vault and buried six feet
below the surface.
“Because
the western part of the country regularly experiences earthquakes, that
region has dozens of permanent seismometers to observe fault
movements,” says Bob Woodward, director of the USArray, the seismic
component of EarthScope.
“Seismic
stations in the eastern third of the U.S. are much less common,
although earthquakes do occur, as we all learned last August.”
Transportable
Array seismometers are extremely sensitive. They can detect earthquakes
at magnitude 5.0 or greater—”sensing” them as far away as the opposite
side of the planet—as well as record smaller quakes that occur
regionally and locally.
Each station includes a high-performance barometer and an infrasound microphone, and sensors to record temperature and pressure.
Data
collected by the station’s instruments are transmitted in real-time to
the Array Network Facility at the University of California, San Diego,
then archived at the IRIS (Incorporated Research Institutions for
Seismology) Data Management Center in Seattle for use by researchers
around the world.
From its underground crypt, 457A will be sending messages to geologists–and to all of us.
