# Seismicity

Seismicity is a measure which encompasses earthquake occurrences, mechanisms, and magnitude at a given geographical location.[1] 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.

## Calculation of seismicity

Seismicity is quantitatively computed. Generally the region under study is divided in equally sized areas defined by latitude and longitude and the interior of the Earth is divided into various depth intervals on account of Earth's layering: Up to 50 km depth, 50–300 km, and > 300 km.[2]

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

${\displaystyle {E_{s0}}_{i}}$: is the energy of a single seismic event (i.e., earthquake);
${\displaystyle {\delta \phi }_{0}}$: interval of latitude;
${\displaystyle {\delta \lambda }_{0}}$: interval of longitude
${\displaystyle {\delta h}_{0}}$: interval of the hypocenter;
${\displaystyle {\delta t}_{0}}$: interval of the time of the seismic event.
The result is seismicity as energy per cubic unit.