Earthquakes Can Cause Remote Events Worldwide
Kris Pankow, a seismologist at the University of Utah, analyzed 15 major M7.0 or greater earthquakes that have occurred since 1992 and found that in many cases, the quakes were directly responsible for causing smaller earthquakes hundreds or thousands of miles away.
Source: Aaron Velasco, University of Texas at El Paso
â€œPreviously it was thought seismically active regions or geothermal areas were most vulnerable to large earthquake triggers,â€ says Kris Pankow, a seismologist at the University of Utah Seismograph Stations and a co-author of the new study.
But Pankow and colleagues analyzed 15 major earthquakes stronger than magnitude-7.0 since 1992, and found that at least 12 of them triggered small quakes hundreds and even thousands of miles away, according to the findings published online Sunday, May 25, 2008 in the journal Nature Geoscience.
â€œWe conclude that dynamic triggering is a ubiquitous phenomenon,â€ they wrote.
Pankow conducted the study with seismologist Aaron Velasco and undergraduate student Stephen Hernandez, both at the University of Texas at El Paso; and seismologist Tom Parsons, of U.S. Geological Survey in Menlo Park, Calif.
They analyzed data from more than 500 seismic recording stations five hours before and five hours after earthquakes that registered more than 7.0 on the â€œmoment magnitudeâ€ scale, which scientists say is the most accurate scale for large earthquakes. (The frequently cited Richter scale measures only relatively small, nearby quakes).
The data â€“ obtained from the Incorporated Research Institutions for Seismology, a consortium of universities â€“ included 15 major earthquakes from 1992 through 2006, including the 1992 Landers quake in California 800 miles southwest of Yellowstone, the magnitude-7.9 Denali fault quake in Alaska in 2002, and the magnitude-9.2 Sumatra-Andaman Islands quake near Indonesia in 2004 that generated a catastrophic tsunami blamed for most of the quakeâ€™s 227,898 deaths in South Asia and East Africa.
Scientists previously noted that those three major quakes triggered not only nearby aftershocks, but small quakes at great distances. The new study is the first to systematically analyze all the worldâ€™s big quakes during 1992-2006 and find that most of them triggered distant, smaller tremors. These are different than aftershocks, which occur fairly close to the main quake. After the devastating 2004 Sumatra earthquake, triggered quakes even occurred in Ecuador, on the opposite side of the Earth.
Similar Posts on Geology News:
- Sichuan Quake Ruptured in 2 Stages
- Rocking and Rolling in the Bay Area
- Predicting Deep Sea Earthquakes
- New Forecast for California Earthquakes
- No Evidence for Large Triggered Earthquakes Across the Globe