Seismology

Searching for Clues Along the Ring of Fire


Some scientists predict that the 9.0-magnitude Richter-scale quake in Japan will touch off even more Pacific temblors in the years ahead. It's a frightening prospect, yet also an opportunity for seismologists and geophysicists trying to unlock the secrets of a mosaic of fault lines along the Pacific Rim, the world's most quake-prone region.

Japan's quake released so much energy that it is estimated to have shifted the planet's axis by nearly 4 inches (10 centimeters), according to the National Institute of Geophysics and Volcanology in Rome. The U.S. Geological Survey estimates the seismic event actually moved the coastline of the country's main island of Honshu by eight feet.

The quake may have also shifted pressure points between the undersea Pacific and North American plates that meet 500 kilometers to the east and west of the epicenter near Sendai. That's likely to create aftershocks "for a long time," says Eric Fielding, a principal scientist at the Jet Propulsion Laboratory. The Pasadena (Calif.) research group is using data from Japan to help scientists forecast follow-on shifts in tectonic plates.

The more quakes there are, the more seismologists can learn about the seismic movements, called slips, among tectonic plates in the region, a critical step in developing better models to predict earthquakes. Scientists measure plate slips to determine how fault lines interact with each other. The disasters "have given us a huge amount of high-quality data that [were] not available before," Andreas Reitbrock, a professor who teaches about the Earth's interior dynamics at the University of Liverpool, wrote in an e-mail. "Due to the new data available, we are now beginning to understand in much more detail the actual slip distribution before, during, and after such huge tremors."

There has been no shortage of major earthquakes in recent years to study, including a 6.3-level New Zealand quake in February that leveled parts of Christchurch and killed 160. In 2004, a 9.1-magnitude temblor in Sumatra, Indonesia, set off a tsunami in the Indian Ocean that left about 220,000 dead or missing in 12 countries. Aftershocks from that earthquake continued for years and killed hundreds more.

Data generated from these massive earthquakes have given scientists better insights into the dynamics of the Pacific Rim's so-called Ring of Fire, an arc of fault lines, ocean trenches, and volcanoes extending from Indonesia to South America. "Before 2004, most geophysicists taught that only limited parts of the Ring of Fire could be capable of generating really giant earthquakes," Antonio Piersanti, head researcher of the National Institute of Geophysics and Volcanology, said in an e-mail. "After the Sumatra event, and especially after this last event, maybe we should seriously consider the possibility that any part of the Ring of Fire could generate a 9-plus earthquake."

Scientists caution that predicting whether and when a plate may pop up or dive underneath another is still beyond their reach. One big worry for Japan is whether the fault line closer to Tokyo has become more unstable. "It is possible that the portion of the plate boundary closer to Tokyo is now closer to failure, though it is rather difficult to say when that failure might occur and how large it might be," says Brian Baptie, a British Geological Survey scientist.

The bottom line: Japan's earthquake will generate aftershocks for years, producing data that may yield insights about the quake-prone Pacific Rim.

Tirone is a reporter for Bloomberg News in Vienna.

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