First-of-its-kind experiment: The San Andreas Fault Gravity Gradiometer Project

Sep 07, 2004
The San Andreas Fault Gravity Gradiometer Project

Using classified technology developed by the military during the Cold War, a team of geoscientists led by Rice University's Manik Talwani is conducting a first-of-its-kind experiment on California's famed San Andreas fault this week. The researchers will gather data that could give scientists a much clearer picture of the fault's "gouge zone," a region 2-3 kilometers beneath the earth consisting of gravel-sized rock that is created when continental plates grind against one another.

Little data has been collected on the deep underlying structures of fault lines because it's very expensive to drill deep wells and install instruments that far below ground. This week's experiments take advantage of extremely sensitive gravity instruments that will be flown over the site in an airplane. By taking to the air, Talwani and his colleagues will be able to cover a 100-square kilometer region of the San Andreas near the town of Parkfield, in central California.

"If this technique works, it will open the door for geoscientists to affordably gather information about fault lines and other subsurface areas of interest," said Talwani, the Schlumberger Professor of Geophysics. "Moreover, these flights will give us a baseline measurement that we can compare with future surveys to find out how things are changing in the shallow crust beneath the surface of the fault."

The experiments take advantage of the fact that gravity varies slightly over the Earth's surface, due to small changes in the mass of subsurface rock and sediments. Using sophisticated instruments developed for nuclear submarines during the Cold War, the research team will measure the gravity gradient, or the rate at which gravity changes from place to place along the San Andreas.

The flights are being conducted near Parkfield, because that is the site of the International Continental Drilling project, a scientific mission that's taking core samples within the region that Talwani's team is measuring. This physical evidence will help Talwani's team as it analyzes its data.

Ultimately, Talwani hopes the technology will change the economics of studying fault lines by making it affordable to conduct baseline and follow-up surveys of significant portions of fault lines -- something that just isn't cost effective with land-based instruments.

The gravity gradiometer that's being used this week was developed at great expense by Lockheed-Martin during the Cold War. It was originally developed as a silent navigation system for nuclear submarines, and some of the underlying technology of the instrument remains classified.

Talwani's group is contracting with the Houston-based Bell Geospace Inc. to carry out the airborne gradiometer survey. The project is supported by the National Science Foundation, the National Imagery and Mapping Agency and several industrial firms.

More information about the San Andreas Project is available at: cohesion.rice.edu/naturalsciences/earthscience/research.cfm?doc_id=2815

Explore further: Bright points in Sun's atmosphere mark patterns deep in its interior

add to favorites email to friend print save as pdf

Related Stories

Charting Icelandic glacier dynamics

Mar 14, 2014

Mark Simons, professor of geophysics at Caltech, along with graduate student Brent Minchew, recently logged over 40 hours of flight time mapping the surface of Iceland's glaciers. Flying over two comparatively ...

Eight seconds of terror

Jan 17, 2014

(Phys.org) —Twenty years ago this week, in the predawn darkness of Jan. 17, 1994, at five seconds before 4:31 a.m. PST, the ground ruptured violently on a blind thrust fault (a crack in Earth's crust that ...

Recommended for you

Astronauts to reveal sobering data on asteroid impacts

11 hours ago

This Earth Day, Tuesday, April 22, three former NASA astronauts will present new evidence that our planet has experienced many more large-scale asteroid impacts over the past decade than previously thought… ...

Rosetta instrument commissioning continues

11 hours ago

We're now in week four of six dedicated to commissioning Rosetta's science instruments after the long hibernation period, with the majority now having completed at least a first initial switch on.

Astronaut salary

12 hours ago

Talk about a high-flying career! Being a government astronaut means you have the chance to go into space and take part in some neat projects—such as going on spacewalks, moving robotic arms and doing science ...

User comments : 0

More news stories

Cosmologists weigh cosmic filaments and voids

(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational ...

Hubble image: A cross-section of the universe

An image of a galaxy cluster taken by the NASA/ESA Hubble Space Telescope gives a remarkable cross-section of the Universe, showing objects at different distances and stages in cosmic history. They range ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Deadly human pathogen Cryptococcus fully sequenced

Within each strand of DNA lies the blueprint for building an organism, along with the keys to its evolution and survival. These genetic instructions can give valuable insight into why pathogens like Cryptococcus ne ...