An
earthquake in a
volcanically active area with an origin different from that of a
tectonic earthquake.
Possible origins include the modification of regional stress by magma, volcanic eruption, the oscillation of liquid and/or gas in a magma chamber and magma flow in conduits compressed by hydrostatic pressure.
In the most common form, a volcanic earthquake usually accompanies a volcanic eruption. The earthquake preceeding or following an eruption is usually a form of pressure release. Occasionally, it is the result of magma eroding structural bedrock and causing a weakness in the surrounding earth.