Sunday, October 7, 2012

Big earthquakes can trigger temblors across globe, USGS says. By Susanne Rust

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A large earthquake in one part of the globe can trigger earthquakes elsewhere, according to new research by scientists from the U.S. Geological Survey and UC Berkeley.

The global aftershocks are fairly immediate, taking place within a week of the original large quake, the researchers said. And the observation might require seismologists to change their definition of an aftershock, from one that stresses quakes caused in the immediate region of an earthquake to one that can occur anywhere.

“Earthquakes are immense forces of nature, involving complex rock physics and failure mechanisms occurring over time and space scales that cannot be re-created in a laboratory environment,” USGS Director Marcia McNutt said in a press statement.

“A large, unusual event such as the East Indian earthquake last April is a once-in-a-century opportunity to uncover first order responses of the planet to sudden changes in state of stress that bring us a little closer to understanding the mystery of earthquake generation,” she said.

The research was published this week in the journal Nature.

In April, a magnitude 8.6 earthquake struck the East Indian Ocean along a strike-slip fault – the largest earthquake ever recorded on a strike slip and 10 times larger than any previously recorded strike-slip quake.

"If you asked any of us if this event is possible a year ago, we would have laughed at you," said Thomas Heaton, a seismologist at the California Institute of Technology, who was not involved with the current study. "Because this was such an unusual event, it radiated very large seismic waves globally."

In the six days that followed the April quake, the number of earthquakes across the globe that were magnitude 5.5 or larger increased nearly fivefold.

“This was a really surprising finding,” said Fred Pollitz, a seismologist with the USGS and lead author of the paper. “We’d been telling people for years that this sort of thing couldn’t happen.”

Other quakes that have equaled or exceeded magnitude 8.5 have increased the number of magnitude 5.5-or-greater quakes globally, but only at one-third the rate as this year's quake ... Read the full story by Susanne Rust in California Watch

Author: Susanne Rust is an investigative reporter for California Watch and the Center for Investigative Reporting focused on the environment ...more
Infographic:  U.S. Geological Survey and UC Berkeley│Mercury News

1 comment:

  1. This isn't new research; it was proven quite some time ago, just as Earthquake Patterns were claimed to be Junk Science by the USGS which have also been proven to be correct.

    William Cormier