There is no evidence that earthquakes are becoming more frequent, it is simply that more earthquakes are being recorded, especially small ones, as extensive world-wide monitoring networks continue to expand. The number of large earthquakes, however, remains stable year in and year out. The Earthquake Hazards Program (USGS) website provides data on the frequency of earthquake occurrences.
Officials at the USGS estimate that several million earthquakes occur in the world each year. But many go undetected because they occur in remote areas or have very small magnitudes. The USGS National Earthquake Information Centre locates about 50 earthquakes each day, or about 20,000 a year. Up-to-date statistics on the number of earthquakes worldwide and in the United States can be found in the Earthquake Hazards Program (USGS) website.
British Geological Survey
Earthquake Hazards Program (USGS)
It seems to be a big year for earthquakes so far, with major earthquakes hitting Haiti, Chile, Taiwan and Turkey in a span of two months.
So is the number of earthquakes increasing? According to the United States Geological Survey, no.
The USGS cites a number of reasons why it seems that more catastrophic earthquakes than normal are happening.
Technology has increased the amount of earthquakes that are detected and reported. Today, there are thousands of stations, compared to about 350 in 1931. The increase of stations has allowed scientists to detect earthquakes that would not have been decades ago.
Rapid improvements in global communications have enabled news of an earthquake to spread almost instantly. Several decades ago, the USGS said, it could take weeks after an earthquake to make the newspapers, often landing on the back pages.
Population booms are also contributing the the perception that there are more earthquakes. Many of these population increases are in earthquake-prone areas, so there is a higher possibility of more casualties when a major quake strikes.
"We have not seen any statistical increase in the number of earthquakes if you look back over the tens and hundreds of years," said Paul Earle, a USGS seismologist. "However, unfortunately the recent earthquakes have impacted populated areas, which brings them into the news, and people become more aware of the earthquakes."
In 1960, Haiti had a population of 3.87 million, according to the World Bank data finder. Since then, it has more than doubled to 9.84 million as of 2008.
Since earthquakes tend to happen in "clusters," the USGS also cites the human factor as a contributing reason to the perception of increased earthquakes. A series of strong earthquakes, such as the ones that have taken place so far this year, could simply lead many to believe that there has been an increase in the number.
"After very large earthquakes like this magnitude, 8.8 in Chile, that produces a large number of aftershocks, which gives you an increased number of earthquakes in the magnitude 5.0 and greater range around that time," Earle said. "However, if you look back over a long period of time, we don't see any increase in seismic activity."
Based on records kept since 1900, the USGS expects a yearly total of 17 major earthquakes and one great earthquake. Major earthquakes are those between 7.0 and 7.9 on the Richter scale, while great earthquakes are classified as 8.0 and above.
Since 1990, the amount of major earthquakes has stayed relatively constant. This estimation of 17 quakes has not been exceeded, with the highest number of 16 major quakes occurring in 2009. http://www.accuweather.com/en/weather-news/has-the-number-of-earthquakes/25904 We continue to be asked by many people throughout the world if earthquakes