Live Science (Link) - Jeanna Bryner (February 27, 2010)
Chile is on a hotspot of sorts for earthquake activity. And so the 8.8-magnitude temblor that shook the capital region overnight was not a surprise, historically speaking. Nor was it outside the realm of normal, scientists say, even though it comes on the heels of other major earthquakes.
One scientist, however, says that relative to a time period in the past, the Earth has been more active over the past 15 years or so.
The Chilean earthquake, and the tsunami it spawned, originated on a hot spot known as a subduction zone, where one plate of Earth’s crust dives under another. It’s part of the very active “Ring of Fire,” a zone of major crustal plate clashes that surround the Pacific Ocean.
“This particular subduction zone has produced very damaging earthquakes throughout its history,” said Randy Baldwin, a geophysicist with the U.S. Geological Survey (USGS).
The world’s largest quake ever recorded, magnitude 9.5, occurred along the same fault zone in May 1960.
Even so, magnitude-8 earthquakes occur globally, on average, just once a year. Since magnitudes are given on a logarithmic scale, an 8.8-magnitude is much more intense than a magnitude 8, and so this event would be even rarer, said J. Ramón Arrowsmith, a geologist at Arizona State University.