Earth's got the shakes. What's worse is that the ripple effects from those shudders -- in the form of earthquakes -- kill thousands each year and cause billions of dollars in damage.

Scientists are looking into a satellite system that can spot the stresses and strains of looming earthquakes, perhaps providing short-term forecasting of the vicious events.

On June 22, a strong quake, registering 6.1 Richter scale struck northern Iran, killing and injuring hundreds of people and destroying dozens of villages spread across a mountainous rural area. On Thursday, northern Taiwan was rattled by an earthquake and in Sydney, Australia, public authorities there were recently surprised to find an earthquake fault line next door to the projected construction site of an expensive nuclear reactor.

	Images
	Launched by the European Space Agency (ESA), the Earth Remote Sensing (ERS-2) uses radar system that can watch for day/night earthquake phenomenon around the planet. Click to enlarge.
	Europe's Earth Remote Sensing spacecraft use radar signals that may offer clues in how best to spot earthquakes before they occur. Each cycle of colors (for example, going from yellow to purple to turquoise and back to yellow again) represents a change in the ground-height, dependent on position of spacecraft above Earth. Click to enlarge.
	Digital Tectonic Activity Map shows a world of trouble. Click to enlarge.
	Earthquakes unleash tremendous energy causing billions of dollars of damage worldwide. Click to enlarge.
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Meanwhile, a new study by the largest disaster relief organization -- the International Federation of Red Cross and Red Crescent Societies -- calls for early warning systems to help avert human and economic losses from Mother Nature's nasty knock-out punches, be they from earthquakes, hurricanes, floods or droughts.

Congress allocated $2 million in 2000 to NASA, kick-starting an assessment of how space technology can be on the lookout for imminent earthquakes. The outcome is the Global Earthquake Satellite System (GESS) study.

What has scientists excited is the advent of satellite synthetic aperture radar interferometry. That's a mouthful but also labeled simply as InSAR. The technique has proven revolutionary.

InSAR relies on image pairs to derive displacements to the resolution of radar wavelength. Topography changes can thus be observed, like crustal deformation, particularly when combined with continuous Global Positioning System (GPS) satellite arrays.

Boosting confidence in the idea is radar data churned out by European Remote Sensing Satellites. ERS-1 and ERS-2, respectively launched in 1991 and 1995, clearly revealed complex deformation fields of many earthquakes. ERS sensors gathered evidence of stress transfer and earthquake triggering between neighboring faults in southern California.

The GESS study focuses on a dedicated InSAR system. Having the hardware in orbit would lead to greater understanding of earthquake physics and better earthquake hazard assessments, said Carol Raymond, a geophysicist at the Jet Propulsion Laboratory in Pasadena, California. She is leading the GESS study effort.

Now underway, Raymond said, is production of a 20-year roadmap for earthquake monitoring from space. "We have focused our efforts on interferometric synthetic aperture radar techniques as these appear most promising," she told SPACE.com.

A first step is placing in low Earth orbit a single "pathfinder" mission that is optimized for earthquake studies. That would be followed by a set of satellites operating at low altitude, orbiting in such a way as to maximize coverage. Finally, a small constellation of higher altitude spacecraft would churn out higher quality data and have operational flexibility, Raymond said.

Some of the GESS study is directed towards technology development. Large deployable antennas and advanced processing systems are under review, as is coming up with ways to enhance remote sensing of Earth from space.

GESS study members are also looking into other types of measurements. Susceptibility of terrain to shaking, liquefaction hazards, landslide vulnerability are part of the review. Possible precursory signals to a quake are being studied too, such as changes in Earth's magnetic field; enhanced heat flow in the ground; even reported flashes of light. These types of phenomenon could be forewarning indicators.

How soon could GESS be up and operating?

The high-orbit, high-performance radar mission could be launched within a decade, perhaps less, given funding, Raymond said. "The low Earth orbit constellations are absolutely doable now if funds were allocated," she said.

Earthquake prediction is a tough assignment, contrasted to forecasting, said Paul Lowman, a geophysicist in the Geodynamics Branch at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

"If you're doing earthquake prediction, you've got to come up with time, place, and magnitude. If you miss any one of those three, you haven't really made much of a prediction," Lowman told SPACE.com.

The approach now, Lowman said, is picking a specific area and give some idea of the probability of a sizeable quake within some reasonable time frame.

Lowman is author of the long awaited tome, Exploring Space, Exploring Earth. The book is set for release this August by Cambridge University Press and details the extraordinary findings about Earth gleaned from decades of space research.

The combination of orbiting hardware, novel space geodesy techniques, GPS, and a range of airborne and ground gear is a potent new way to study earthquakes, Lowman said. "You should be able to focus on areas from space that you might say would be flashing yellow. That means you better take a harder look at those places and get there with ground equipment," he said.

Considerable attention is paid to "interplate" boundaries in regions like Southern California, and other spots around the Ring of Fire of the Pacific Ocean basin. These areas are where the edges of tectonic plates collide, and are marked by concentrations of earthquakes.

But attention should also be paid to "intraplate" tectonics too, said Jacob Yates, a scientist within NASA Goddard's Geodynamics Branch. He along with Lowman point out that some of the most catastrophic earthquakes on record did not occur along plate boundaries.

Yates and Lowman see GESS as instrumental in monitoring intraplate activity, especially in remote regions of the world. Unfortunately, many of the most devastating earthquakes of the 20th century occurred at the intraplate level in Third World countries, Yates told SPACE.com.

Intraplate earthquake areas deserving of study include the Hudson Bay, Australia, the Ural Mountains, and the Aegean Sea. Understanding intraplate earthquakes would be a very effective use of the GESS mission, Yates said.

A co-investigator on intraplate crustal dynamic study for GESS, Yates said that space radar technology has matured greatly over the years.

"It's time to take the next step at looking at vertical and horizontal motion from InSAR to determine crustal motion. I'd say that InSAR is the way to go for monitoring sudden changes in crustal motion that may be precursors to seismic motion or volcanic activity," Yates said.

While GESS would operate around the clock, Lowman said, there's no doubt that even forecasting earthquakes will not be easy. Great care must be taken in not issuing false alarms.

"I think, eventually, we'll get to the point where earthquakes can be predicted. But even today, it's going to be years down the road," Lowman said.

Then there's the need to provide GESS-generated data in a timely manner to responsible governments and agencies. That is key if government-driven disaster preparedness and planning is to be successful.

"It gets much more complicated than just science," Lowman said.