A recent U study suggests that large earthquakes can trigger smaller quakes in areas not prone to them and on opposite sides of the world, possibly explaining the aftermath of the recent quakes in Asia.
The devastating earthquake in Sichuan, China, might have created other smaller earthquakes and events in distant places, said Kris Pankow, a research professor of geology and geophysics. "Our paper suggests that there were triggered events throughout the world following that (quake)."
The study also concluded that earthquakes do trigger other earthquakes in geothermal areas and areas that have frequent or intense earthquakes.
"Magnitude 7 earthquakes are triggering earthquakes around the globe," Pankow said.
The study, completed in January, analyzed data from 500 different seismic stations five hours before and five hours after earthquakes measuring more than 7.0 on the moment magnitude scale. Scientists believe this scale is more accurate for measuring large earthquakes than the commonly used Richter scale.
Stephen Hernandez, a student at the University of Texas at El Paso who participated in the study, said one significant finding from the study is that large quakes are only triggering smaller quakes.
"The events being triggered by large earthquakes are mostly only magnitude 4 and smaller earthquakes," he said.
Larger earthquakes triggering smaller earthquakes hasn't happened only in isolated cases.
"It's happening all over the world, and it's happening following probably most magnitude 7 and larger earthquakes," Pankow said.
After the Landers, Calif., earthquake in 1992, seismologists had to change the way they thought about earthquakes.
"Up until 1992, if you were to ask a seismologist if an earthquake in California could cause an earthquake in Utah he would have said absolutely not," Pankow said. "Then Landers happened, and it triggered earthquakes in southern Utah, and it triggered earthquakes as far away as Yellowstone."
Pankow said a significant finding in this study is that there is a direct correlation between when the peak in the triggered activity occurred and when the first of the surface waves came through.
"We can now take the physics of the surface waves and start to look at what actually causes an earthquake," he said.
Pankow co-wrote the study with fellow seismologist Aaron Velasco and Hernandez, both at the University of Texas at El Paso. Tom Parsons, who works with the U. S. Geological Survey in Menlo Park, Calif., also participated in the study.
a.cone@chronicle.utah.edu
