The United States Geological Survey released some disturbing information this week about the impact of large earthquakes. The USGS said two new studies show quakes half a world away can trigger aftershocks locally.
Until now, distant but damaging “aftershocks” have not been included in hazard assessments. The studies may change that industry standard.
The studies came from research centered on the largest earthquake in 2012. A magnitude 8.6 hit in the East Indian Ocean in April. That earthquake triggered aftershocks as far away as Mexico and Japan.
The USGS also found an extraordinary number of earthquakes of magnitude 4.5 and greater in the six days following the April quake. (See graphic below).
"Earthquakes are immense forces of nature, involving complex rock physics and failure mechanisms occurring over time and space scales that cannot be recreated in a laboratory environment," said USGS Director Marcia McNutt in a 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."
The type of earthquake that can trigger other quakes half way around the world only hit once every 50 years or so.
Study co-author Fred Pollitz told the Bay Area News Group it is possible that a large shaker on the other side of the globe could trigger earthquakes on both the Hayward and the San Andreas faults.
Fellow author and professor of earth and planetary science at the University of California at Berkeley agrees about the local impact. "This study now says that, while it is very rare -- it may only happen every few decades -- it is a real possibility if the right kind of earthquake happens," Roland Burgmann said in a statement to the paper.