Scientists have traveled about 60 percent of the way in what they call a modern-day journey to the center of the Earth, an approximately 3-mile drill hole alongside and across California's San Andreas Fault to explore earthquakes.
The drilling in Monterey County began June 11, and it had traveled 8,250 feet into the Earth by last week, when the National Science Foundation and the U.S. Geological Survey gave the media a tour of the their joint project.
Engineers plan to drill about 2 miles vertically and then about 1 mile horizontally _ at a 55-degree angle _ to intersect the San Andreas Fault.
They will line the hole with pipe and concrete and insert tools deep underground to create the world's first underground observatory of an active fault, the San Andreas Fault Observatory at Depth.
"This operation is essentially the Hubble Telescope underground," said Rep. Sam Farr, D-Calif.
The observatory is part of the $236-million EarthScope project, a combination of seismographic stations, global positioning systems and other instruments placed around the United States to record and report on the Earth's movement and stresses from its crust to its core.
Scientists hail EarthScope as the largest systematic survey of the North American continent since the Lewis and Clark expedition 200 years ago.
"We are standing on a planet with a million mysteries," said Arden Bement Jr., acting director of the National Science Foundation. "We have a long way to go to understand them." At the San Andreas observatory alone, scientists expect to gather enough data each day to fill 100 400-page novels, or 40 DVDs.
They plan to measure movement, stress, core pressure and water content in the Earth. They also plan to collect fluids, gas and other samples to better understand the ground around the fault.
With the information, scientists hope to determine if earthquakes can be predicted and how to build safer buildings by figuring out how tremors move through soil and rock.
"We are going to be monitoring these earthquakes for 20 years and answering questions that have been unanswerable for decades," said Mark Zoback, a Stanford University professor of geophysics.
The $20-million observatory is EarthScope's most extensive operation at one site. It is about 1,800 feet from the San Andreas Fault, the juncture between the Pacific and the North American plates.
The two plates rub sideways against each other, triggering small and large quakes.
In this part of the state, small tremors are such a common occurrence that the nearby community of Parkfield bills itself as the "Earthquake Capital of the World."
Crews are working on a huge drilling rig, using 12\-inch drill bits. Drilling mud drives the earth that is excavated to the surface.
Farr, who toured the site, called it a "remarkable" project that will allow scientists to complete the exploration Lewis and Clark began.
"We have gone the lineal distance," he said. "Now we are going the vertical distance."