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EarthScope Peeks Beneath the Crust


SAFOD rig, August 2004

Drilling rig at SAFOD site is 60 meters tall, August 2004.

Photo (c) Andrew Alden, licensed to About.com (fair use policy)

The beauty of funding science with public money is that groups of scientists can carry out large-scale, pathbreaking projects that pay back the investment many times over in unexpected ways. The space program is full of examples, but there's one in the works that promises "a new view into Earth." It's EarthScope, a major initiative funded by the National Science Foundation that aims to take the best current technology and theory and concentrate them downward on the whole North American continent.

The multiyear project has three parts, designed to complement each other as well as push science forward on their own.


The first element is a longtime dream of earthquake researchers—to drill a hole deep into an active fault zone and place instruments where earthquakes are born. This project is the San Andreas Fault Observatory at Depth, or SAFOD. The aim of SAFOD is to use the latest tricks from the oil companies to drill a curved shaft across this notorious fault at a site near Parkfield, in central California. Then the latest generation of miniaturized smart sensors will be placed in the hole to monitor conditions where no one has gone before. The three photos accompanying this article are from the SAFOD site in August 2004.


Second is "a Hubble telescope into Earth," a portable network of advanced seismographs called USArray. A grid of hundreds of instruments will be laid down like a doctor's stethoscope on different patches of the American countryside for six months at a time, building pictures in kilometer-scale detail of the whole thickness of the crust.

Over its ten-year life this traveling scientific show will come near the hometown of every American. It will be the first truly systematic exploration of the continent's crust. Local press and local educators will get citizens involved everywhere USArray goes. (Read more about it in this article.)


Third is a similar network of sensors, the Plate Boundary Observatory or PBO, to be placed permanently on the parts of the western United States where the Pacific and North American plates meet. Although most of the motion between the two plates is on the San Andreas fault zone, much of it is spread across a wider region extanding far eastward.

The PBO network will precisely measure crustal movements from the west coast to Wyoming. Instruments will include special seismometers, strainmeters, and hundreds of receivers tied to the Global Positioning System (GPS) satellite network. These instruments measure immediate, short-term, and long-term motions respectively. They would be most useful for studies of earthquakes and volcanic activity. Together, some 1,000 instruments will map the crust's motions to an accuracy of a millimeter per year or so. Mexico and Canada are preparing to join the program too.

EarthScope had to pass muster with the National Science Board and the White House, the agencies that judge the priority of large research proposals. The president's budget request included it three times, but Congress kept letting projects from other fields—space, physics, ecology—push EarthScope out of its place in line. Finally the money was pledged to the National Science Foundation, and the work is under way.

EarthScope relies on the old wisdom, proved many times, that new instruments reveal new science. Here's another example from paleontology—a study, using advanced tools, of a single fossil horse tooth.

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