Seismicity is a measure encompassing earthquake occurrences, mechanisms, and magnitude at a given geographical location. As such, it summarizes a region's seismic activity. The term was coined by Beno Gutenberg and Charles Francis Richter in 1941. Seismicity is studied by geophysicists.

Seismicity is quantitatively computed. Generally, the region under study is divided in equally sized areas defined by latitude and longitude, and the Earth's interior is divided into various depth intervals on account of Earth's layering: Up to 50 km (31 mi) depth, 50–300 km (31–186 mi), and > 300 km (190 mi).

The usual formula to calculate seismicity is:

$${\displaystyle S={\frac {\sum _{i}{E_{s0}}_{i}}{\delta \phi _{0}\,\delta \lambda _{0}\,\delta h_{0}\,\delta t_{0}}}}$$

where