U.S. space agency scientists say they've used satellite data to observe, for the first time, the healing of subtle, natural surface scars from an earthquake.

The 6.6 magnitude earthquake occurred at Bam, Iran, in 2003 on a buried fault and killed more than 30,000 people.

National Aeronautics and Space Administration geophysicist Eric Fielding and colleagues analyzed radar images from the European Space Agency's Envisat satellite to study the land surface above the fault that's buried about half a mile below the Earth's surface. They said they discovered a shallow, narrow surface depression that formed and then evolved after the quake.

Fielding said the results have implications for assessing the risk of future earthquakes associated with known buried faults.

The study is also helping researchers anticipate the future behavior of the fault. Initially, they said they were concerned that if stress at depth wasn't relieved at the surface, a subsequent earthquake could result. But because the rupture's stress was absorbed in the damage zone, as indicated by the depression, the researchers believe the fault is no longer a risk.

The research that included Paul Lundgren, Roland Burgmann and Gareth Funning appears in the journal Nature.