Is the number of earthquakes increasing?
No, the number of earthquakes is not increasing compared with the recorded history, according to data from the US Geological Survey National Earthquake Information Center. See: Are Earthquakes Really on the Increase?
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. There are more seismographs installed worldwide every year, so more earthquakes can be detected. However, the number of large earthquakes (magnitude 6.0 and greater) has stayed relatively constant. See: Number of Earthquakes Worldwide for 2000 – 2010
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. (source: USGS)
How Often Do Earthquakes Occur?
Worldwide, strong earthquakes happen more than once per month. Smaller earthquakes, such as magnitude 2 earthquakes, occur several hundred times a day. To create a mountain system might take several million medium sized earthquakes over tens of millions of years. Read more
The USGS provides a nice summary of historical earthquake activity. Go to Earthquake Facts and Statistics
Frequency of Occurrence of Earthquakes
|7 – 7.9||17 2|
|6 – 6.9||134 2|
|5 – 5.9||1319 2|
|4 – 4.9||13,000 (estimated)|
|3 – 3.9||130,000 (estimated)|
|2 – 2.9||1,300,000 (estimated)|
1 Based on observations since 1990.
2 Based on observations since 1990.
Dr. Michael Blanpied, from the USGS Earthquake Hazards Program, answered questions from the public about the causes of recent earthquakes. Read The Washington Post article: Seismic Science: Is number of earthquakes on the rise?