The number and magnitude of earthquakes is not increasing. Our ability to detect them is greatly increasing. They are also being reported by the news media more rapidly and covered more widely.
Earthquakes of the magnitude of the Haiti and Chile quakes happen on the average 2 to 3 times per year. It is just coincidence that these two occurred closely together.
"The USGS estimates that several million earthquakes occur in the world each year. Many go undetected because they hit remote areas or have very small magnitudes. The NEIC now locates about 50 earthquakes each day, or about 20,000 a year.
As more and more seismographs are installed in the world, more earthquakes can be and have been located. However, the number of large earthquakes (magnitude 6.0 and greater) has stayed relatively constant.
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; today, there are more than 8,000 stations and the data now comes in rapidly from these stations by electronic mail, internet 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 earthquakes more rapidly and to locate many small earthquakes which were undetected in earlier years. The NEIC now locates about 20,000 earthquakes each year or approximately 50 per day. Also, because of the improvements in communications and the increased interest in the environment and natural disasters, the public now learns about more earthquakes.
According to long-term records (since about 1900), we expect about 17 major earthquakes (7.0 - 7.9) and one great earthquake (8.0 or above) in any given year."
According to the USGS website we expect that earthquakes will occur in the following frequency:
Magnitude -- No/Year-- Examples
8 and higher ---1 --------Chile 2010 (8.8), Chile 1960 (9.5), Alaska 1964 (9.2)
7 - 7.9 ----------17-------- Haiti 2010 (7.0)
6 - 6.9 ---------134
5 - 5.9 --------1319
4 - 4.9 --------13,000
3 - 3.9 ------130,000 -----Illinois 2010
2 - 2.9 -----1,300,000