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A building collapsed due to an earthquake in California |
The aftershocks following earthquakes are becoming larger and occurring over a much wider area than previously concluded, according to a research study published in the British journal Nature.
Seismologists examined data on earthquakes that occurred in California, USA, from 1984 to 2002. They found that aftershocks typically occur within five minutes after the main quake and up to about 50 kilometers from the epicenter for earthquakes rated between 2 and 4 on the Richter scale. Traditionally, it is believed that aftershocks are caused by changes in tectonic pressure.
However, analyses of aftershocks in California indicate that the patterns of these aftershocks are becoming increasingly unclear, suggesting that tectonic pressure can spread over a very wide area, much like ripples in water when a pebble is dropped into a pond.
Q.HƯƠNG
