U.S. researchers studying deep earthquake faults in the Earth report they've discovered a "runaway" effect that allows tremors far below the surface to spread.

Analyzing seismic data from a region in Colombia with a high concentration of intermediate-depth earthquakes, scientists at MIT, working with colleagues from Stanford University, report they've identified a "runaway process" in which the sliding of rocks at great depths causes surrounding temperatures to spike.

Intermediate depth earthquakes originate at between 30 miles to 180 miles below the surface.

The creation of heat by sliding rocks at that depth in turn encourages more sliding -- a feedback mechanism that propagates through the region of the fault, generating an earthquake, the researchers said.

Once thermal runaway starts, the surrounding rocks can heat up and slide more easily, raising the temperature very quickly, they said.

"What we predict is for medium-sized earthquakes, with magnitude 4 to 5, temperature can rise up to 1,000 degrees Centigrade, or about 1,800 degrees Fahrenheit, in a matter of one second," MIT geophysics Professor German Prieto said. "It's a huge amount. You're basically allowing rupture to run away because of this large temperature increase."

The study has been published in the journal Geophysical Research Letters.