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Understanding earthquakes

The recent earthquakes in Turkey, Taiwan and southern California were the most monitored in history, but months later scientists are just beginning to understand the data. A record number of instruments on the ground and in space analysed every quiver of the ground before, during and after the earthquakes, but their measurements did not always match with each other or with predictions of what should have happened. Instead of being disappointed with the results, researchers see the disasters as a unique opportunity to improve their understanding of how quakes are triggered.

For example, in the earthquake that struck southern California on October 16, 1999, nobody was killed and little damage was reported. Measurements taken by global positioning satellites revealed that most of the displacement was on the southern end of the little known Lavic Lake fault. But radar data from a European satellite showed more action at the northern end. "We don't know how to reconcile these two fundamental data sets,' said Mark Simons, a seismologist at the California Institute of Technology, USA. The preliminary findings question the fundamental theories about how faults move during earthquakes, but more analysis will be required before any conclusions are drawn.

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