According to the United States Geological Survey, several million earthquakes occur worldwide each year. It is difficult to refine this estimation to an exact number because many earthquakes go undetected, either because they occur in locations that are uninhabited or barely inhabited, or they are too small in magnitude to be detected by seismographs or other forms of detection.
While the number of smaller earthquakes has seemed to increase over the past decade, the number of earthquakes measuring at a 6.0 magnitude or higher have remained somewhat stagnant. This may be due to the fact that more seismographs have been introduced to areas of the world, allowing scientists to detect and record smaller earthquakes that otherwise would not have been detected. Most earthquakes that have occurred worldwide in the last decade have been calculated between and 2.0 and 5.0 magnitude. Approximately 17 earthquakes measuring above an 8.0 magnitude have occurred in the past 15 years. None of these large earthquakes occurred in the U.S.
The average number of magnitude 5.0 to 7.9 earthquakes occurring worldwide each year is close to 1,500. It is important to note that the U.S. Geological Survey National Earthquake Information Center does not actively locate and record earthquakes with a magnitude of 4.5 or lower occurring outside of the U.S., unless the earthquake causes considerable damage.