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81	Why are we having so many earthquakes? Has earthquake activity been increasing? Tagged: hazards  May  earthquakes  2008  Published: 5/28/2008 Download directly (right-click to save) Type: audio/mpeg File Size: 2398271 bytes

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Welcome to CoreFacts, where we're always short on time and big on science. I'm Jessica Robertson. Alright, let's get right to it. Today's question is...

Why are we having so many earthquakes? Has earthquake activity been increasing/

Although it may seem that we are having more earthquakes, earthquakes of magnitude 7.0 or greater have remained fairly constant throughout this century. A partial explanation may lie in the fact that in the last twenty years, we have definitely had an increase in the number of earthquakes we have been able to locate each year. This is because of the tremendous increase in the number of seismograph stations in the world and the many improvements in global communications.

In 1931, there were about 350 stations operating in the world, and today there are more that 4,000 stations and the data now comes in rapidly from these stations by telex, computer and satellite. This increase in the number of stations and the more timely receipt of data has allowed us and other seismological centers to locate many small earthquakes which were undetected in earlier years, and we are able to locate earthquakes more rapidly. The National Earthquake Information Center now locates about 12,000 to 14,000 earthquakes each year or approximately 35 per day.

Also, because of the improvements in communications and the increased interest in natural disasters, the public now learns about more earthquakes. An increase in earthquake activity does not mean that a large earthquake is about to happen. Similarly, the lack of seismicity does not mean a large earthquake is going to happen.

For more information on earthquake counts by magnitude and year, visit the National Earthquake Information Center's earthquake statistics webpage at neic.usgs.gov/neis/eqlists/eqstats.html.

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