Study: Large Earthquakes Are Not Offset Other Later

NEW YORK - This is good news in the wake of the disaster in Japan: A new study shows that major earthquakes do not trigger another world more dangerous. Large earthquakes are not triggered a local mirror, but the researchers found no sign of fire from medium sized events, beyond 600 miles.

It will not surprise most experts, "says lead study author Tom Parsons. But it differs from his previous research, which is not the overall impact of set-off of small earthquakes," said Parsons, the U.S. Geological Survey Menlo Park, California

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

They saw seismic records across the world for 30 years ending in 2009. There were 205 major earthquakes, with the extent of 7 or more and 25,222 moderates with sizes between 5 and 7

Then the researchers examined the timing of such evidence that large earthquakes triggered events moderated. They have been a delay of up to 24 hours, until the seismic waves in large quakes to dry.

Found an increase in moderate earthquakes, but only about 600 miles from the initial event, and miles in almost all 375. At distances beyond 600 miles, the number of moderate earthquakes after a major event was not higher than normal.

Although the study did not examine whether the large quakes trigger other large earthquakes far, the new data suggest they are not, "said Parsons. Anyway, while only about seven to the world average earthquake size 7 or more per year, such an effect has been observed already, "he said.

The new results agree with what most seismologists believe just experience, "said Klaus Jacob of the Observatory of Columbia University's Lamont-Doherty Earth. "It's nice to see it confirmed by a thorough investigation," said Jacob.

Parsons said the magnitude-9 event in Japan on March 11 was looking at the world map to search for any influence of distant earthquakes. He did not see anything.

"It seems to match what we've seen before," said Parsons.