Here’s some good news in the wake of Japan’s disaster: A new study says big earthquakes don’t set off other dangerous ones around the globe*. Big quakes do trigger local aftershocks*, but researchers found no sign of setting off moderate-sized events beyond about 960 kilometers away.

    That won’t surprise most experts, said lead study author Tom Parsons. But it’s different from his prior research, which did find a global effect for setting off small quakes, said Parsons, of the U.S. Geological Survey in Menlo Park, California.

    Parsons and Aaron Velasco of the University of Texas at El Paso reported the work online Sunday in the journal Nature Geoscience.

    They looked at worldwide earthquake records for the 30 years ending in 2009. There were 205 big earthquakes, with magnitude of 7 or more, and 25,222 moderate ones with magnitudes between 5 and 7.

    Then the researchers looked at the timing of these events for evidence* that the larger quakes triggered* the moderate ones. They checked for delays of up to 24 hours, long enough to let the seismic waves from the big quakes peter out.

    They did find an increase in moderate quakes, but only within about 960 kilometers of the initial event, and nearly all within 600 kilometers.

    While the study didn’t look at whether big quakes trigger other big quakes far away, the new data suggest they do not, Parsons said.

    (SD-Agencies)