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Dictionary.com defines an earthquake as "a sudden movement of the earth's crust caused by the release of stress accumulated along geologic faults or by volcanic activity." As we learned from the numerous resources in our dedicated Full Coverage page on Earthquakes and Volcanoes, these movements are difficult to predict because they give very little advanced warning in terms of seismic activity. Seismologists can make long-term predictions about the probability of occurrence, region, and magnitude of earthquakes. Every year over 150,000 earthquakes are recorded worldwide, and this seismic data is studied to create statistical
predictions. In 1999, for example, the U.S. Geological Survey (USGS) reported there is a 70% chance that one or more quakes of about magnitude 6.7 or larger will occur in the San Francisco Bay Area before the year 2030. The Seismology category in the Yahoo! Directory features several resources from the USGS, including this updated list of the latest earthquake activity and a fascinating article about the Great 1906 San Francisco Earthquake. Current earthquake prediction techniques tend to focus on two fronts: statistical analysis and seismic
monitoring. To date, however, earthquake prediction remains educated guesswork; Japan has spent over a billion dollars in the effort, but the Kobe earthquake in 1995 struck completely by surprise.
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