June 6, 2008
NASA Scientists Achieve Breakthrough For Earthquake Predictions
NASA scientists report being close to a major breakthrough in their work towards developing a method to forecast earthquakes. The researchers discovered a close link between atmospheric electrical disturbances and imminent earthquakes.
Precisely such a signal was observed prior to China's recent catastrophic quake. The NASA team has partnered with British experts to investigate the potential for a space-based early warning system. However, many in the scientific community are skeptical about whether such signals actually indicate an imminent quake.
But physicist Minoru Freund, director for advanced aerospace materials and devices at California's NASA Ames Research Center, believes such a system is indeed possible.
"I do believe that we will be able to establish a clear correlation between certain earthquakes and certain pre-earthquake signals, in an unbiased way," he told BBC News.
"I am cautiously optimistic that we have good scientific data, and we are designing a series of experiments to verify our data," he added.
There are currently no reliably accurate ways to forecast future earthquakes, although most experts agree some type of early warning system would save the lives of tens of thousands.
The signals the NASA researchers are studying occur in the ionosphere, which is different from other layers of the Earth's atmosphere because it is electrically charged through solar radiation exposure. Satellites have frequently detected disturbances in this part of the atmosphere 100-600km above areas that have later experienced earthquakes. Most importantly, they have observed fluctuations in the density of electrically charged ionosphere particles.
A previous study conducted by Jann-Yeng Liu from the Center for Space and Remote Sensing Research in Chung-Li, Taiwan, examined more than 100 earthquakes with magnitudes of 5.0 or larger in Taiwan over several decades. The results of the research showed that almost all of the quakes down to a 35 km depth were preceded by distinct electrical disturbances in the ionosphere.
Although complete details are yet to be released, BBC News reported that scientists also observed a "huge" signal in the ionosphere before China's May 12 magnitude 7.8 earthquake.
NASA researchers have been working with Surrey Satellite Technology Limited (SSTL) in Britain to determine the feasibility of a satellite-based early warning system.
So far, the results look promising.
"The evidence suggests we're now crossing the boundary in terms of technology readiness," Stuart Eves, SSTL's head of business development, told BBC News.
"What we don't know is how big the effect is and how long-lasting it is before the earthquake."
Minoru Freund believes other quake precursors could also be used with the early-warning system, such as anomalies in low-frequency electric and magnetic field data and enhanced emission of infrared (IR) radiation from the quake's epicenter.
Minoru and his father Friedemann Freund, also from NASA Ames Research Center, developed the underlying scientific theory behind these precursors. The theory is based on the idea that when rocks are compressed, which occurs when tectonic plates shift, they behave like batteries, producing electric currents.
"We now pretty much understand the solid-state physics of these rocks," Minoru added.
The theory postulates that the charge carriers consist of pholes, specific type of electrons which laboratory research shows can travel large distances. When the pholes travel to the Earth's surface, it becomes positively charged. And this charge can be strong enough to affect the ionosphere, causing the disturbances observed by satellites.
When these pholes "recombine" at the Earth's surface, they enter an excited state, after which they "de-excite" and emit mid-infrared light particles, or photons, which could explain the IR observations.
"At this point, the connection between the laboratory phenomena and processes at work in the Earth has not been demonstrated and is the subject of research," Dr Mike Blanpied, a geophysicist at the US Geological Survey (USGS), who is not involved with the NASA work, told BBC News.
Blanpied, who is based in Reston, Virginia, criticized the work in two areas. First, the experiments were done on dry rocks at room temperature and pressure. This differs from rock deep in the Earth's crust, which have all their voids filled with mineral solutions and are subjected to high pressures and temperatures. Secondly, the scientists' hypothesis held that fast changes in stress and strain in the crust started a few days before earthquakes. But there has never been an observation of rapid strain changes prior to an earthquake, he said, which means precursor strains before the quakes might be too small to have been detected.
Minoru Freund acknowledged that additional work is needed to improve on the theory, but said he was planning to develop a proposal for a low-cost, space-borne early warning system based on at least three satellites.
Image Courtesy Wikipedia
On the Net:
Nasa Ames Research Center
Nasa Goddard Space Flight Center
Surrey Satellite Technology Limited