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!
GPM sees deadly tornadic storms moving through US Southeast
01.12.2016 | NASA/Goddard Space Flight Center
Cyclic change within magma reservoirs significantly affects the explosivity of volcanic eruptions
30.11.2016 | Johannes Gutenberg-Universität Mainz
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy