Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Satellite data reveals gravity change from Sumatran earthquake

For the first time, scientists have been able to use satellite data to detect the changes in the earth's surface caused by a massive earthquake.

The discovery, reported in the latest issue of the journal Science, signifies a new use for the data from NASA's two GRACE satellites and offers a possible new approach to understanding how earthquakes work.

The research paints a clearer picture of how the earth changed after the December, 2004 Sumatra-Andaman earthquake, the 9.1-magnitude temblor in the Indian Ocean which caused a deadly tsunami killing nearly 230,000 and displacing more than 1 million people.

Centered off the west coast of northern Sumatra, the event followed the slipping of two continental plates along a massive fault under the sea floor. The slippage occurred along 750 miles of the line where the Indian plate slides under the Burma plate, a process called subduction. The quake raised the seafloor in the region by several meters for thousands of square miles.

“The earthquake changed the gravity in that part of the world in two ways that we were able to detect,” explained Shin-Chan Han, a research scientist in the School of Earth Sciences at Ohio State .

First, he said, the quake triggered the massive uplift of the seafloor, changing the geometry of the region and altering previous GPS (global positioning satellite) measurements from the area. Those changes were detectable by GRACE's instruments.

And second, the density of the rock beneath the seafloor was changed after the slippage, and an increase or decrease in density produces a detectable gravity change, Han said.

The GRACE (Gravity Recovery and Climate Experiment) satellites were launched in 2002 and have been gathering global gravity measurements ever since. The identical instruments orbit some 186 to 310 miles (300 to 500 kilometers) above the planet's surface and fly 136 miles (220 kilometers) apart.

The satellites can detect changes in the density of the earth's crust, or in GPS measurements on the ground, and that can now signal changes in the planet's gravity at that point.

Along with colleagues C.K. Shum and Michael Bevis, both professors in the School of Earth Sciences, Han assembled several years of data covering the Indian Ocean region and filtered out seasonal variations. The changing flow of the massive Mekong River, for example, affects gravity measurements for the area and these annual shifts must be removed from the data to detect changes caused by a quake.

The researchers then plugged the data into the latest seismic computer model which painted a picture of gravity increases on one side of the fault line and decreases on the other.

“With this seismic model we were able to explain and interpret the GRACE observations,” Han said, adding that earthquake models are still evolving. “But the observations can also be used to validate the quality of the model itself and therefore improve our knowledge about the solid earth's dynamics.”

The detection of such quakes comes only after extensive data analysis. Real-time detection is far off in the future – if possible at all. And currently, this GRACE technique was applied to understand the mechanism of “great” earthquakes – those exceeding magnitude 9 – which are very rare events.

Detecting “major” quakes – those measuring a magnitude of 7 to 8.9 – which occur frequently is being investigated. NASA's planned extension of the current mission, dubbed GRACE 2, and its enhanced instrumentation should aid in that effort.

However, Han is hopeful that NASA's planned expansion of the current mission, dubbed GRACE 2, and its enhanced instrumentation, might allow the detection of “major” quakes – those measuring a magnitude 7 to 8.9 – which occur frequently.

Chung-Yen Kuo, a post-doctoral researcher in the School of Earth Sciences at Ohio State , and Chen Ji, an assistant professor of earth science at the University of California, Santa Barbara , both participated in the study. Support for this research came from the National Aeronautics Space Administration, the National Science Foundation and the Ohio Supercomputer Center.

Shin-Chan Han | EurekAlert!
Further information:

More articles from Earth Sciences:

nachricht Ice shelf vibrations cause unusual waves in Antarctic atmosphere
25.10.2016 | American Geophysical Union

nachricht Enormous dome in central Andes driven by huge magma body beneath it
25.10.2016 | University of California - Santa Cruz

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

Fluorescent holography: Upending the world of biological imaging

25.10.2016 | Power and Electrical Engineering

Etching Microstructures with Lasers

25.10.2016 | Process Engineering

More VideoLinks >>>