About 1,500 earthquakes of magnitude 5 or greater occur worldwide each year on average. This is a long-term estimate, not a fixed annual quota: some years record more events and others fewer, depending on earthquake clustering, aftershock sequences and improvements in detection.
Magnitude 5 earthquakes are usually large enough to be recorded reliably by seismic networks around the globe, although their effects vary greatly with depth, distance from population centers, local geology and building quality. A magnitude number describes the earthquake’s size at its source; it does not directly state how much damage occurred at the surface.
Earthquake frequency rises sharply as magnitude decreases. Thousands of magnitude-4 earthquakes occur annually, while magnitude-6 events number only around 100 to 150, and magnitude-7 earthquakes occur roughly a few dozen times worldwide. Magnitude 8 or larger earthquakes are much rarer, averaging about one per year. Aftershocks can temporarily inflate the count, but they are still earthquakes included in many global catalogues.