Big Quakes Cause Temblors Worldwide
Pastor Dale Morgan
Big Quakes Cause Temblors Worldwide*
The magnitude 9 Sumatra-Andaman Islands quake near Indonesia in 2004
generated a catastrophic tsunami that washed out villages and was
responsible for many of the quake's 227,898 deaths in 11 countries that
share a coastline with the Indian Ocean.
by Staff Writers
El Paso, TX (SPX) Jun 08, 2008
Scientists have agreed that strong earthquakes produce aftershocks
within the region, but many did not believe that temblors of magnitude 7
and above could trigger smaller quakes on the other side of the world -
until now.
A recent study of major earthquakes since 1992 - the kind that can
generate widespread damage - revealed that such events routinely trigger
smaller jolts around the planet, including areas that are not prone to
quakes.
One example was the 1992 Landers earthquake that was a magnitude 7.3 and
shook up the Southern California desert. The surprise was that it caused
small jolts as far away as Yellowstone National Park - some 800 miles away.
"Earthquakes have been thought of to be very isolated events," Aaron
Velasco, lead author of the study and University of Texas at El Paso
associate professor of geological sciences, said. "Now we're seeing a
relationship between big earthquakes and smaller events around the world."
Velasco and Stephen Hernandez, a UTEP undergraduate student, analyzed 15
major earthquakes stronger than magnitude 7, and found that at least 12
of them triggered small quakes hundreds and even thousands of miles away.
The pair was joined on the study by seismologists Kris Pankow of the
University of Utah and Tom Parsons of the U.S. Geological Survey in
Menlo Park, Calif. The team's analysis was published online Sunday, May
25, 2008, in the journal, Nature Geoscience.
The team analyzed data from more than 500 seismic recording stations
five hours before and five hours after earthquakes that registered more
than 7 on the "moment magnitude" scale, which scientists say is the most
accurate scale for large earthquakes.
The data was obtained from the Incorporated Research Institutions for
Seismology, a consortium of universities, from 1992 through 2006. It
included the Landers quake, the magnitude 7.9 Denali fault quake in
Alaska in 2002, and the magnitude 9 Sumatra-Andaman Islands quake near
Indonesia in 2004.
That last quake generated a catastrophic tsunami that washed out
villages and was responsible for many of the quake's 227,898 deaths in
11 countries that share a coastline with the Indian Ocean.
Scientists previously noted that those three major quakes triggered not
only nearby aftershocks, but small quakes at great distances. In the
case of the 2004 quake, there is evidence that it produced temblors in
Ecuador half a world away.
"This phenomenon has been documented for several isolated events in
certain regions, but now we're able to show that this is occurring
everywhere," Velasco said. "As a result, our ideas about how earthquakes
occur and how we react have to change."