Volcano tectonic earthquake

[3] Usually they are characterised by high seismic frequency and lack the pattern of a main shock followed by a decaying aftershock distribution of fault related tectonic earthquakes.

This means it tends to pool in magma chambers beneath the surface and between the converging tectonic plates.

[4] Where plates diverge such as at mid-ocean ridges the magma also can move into storage chambers and form intrusions again causing shifts in the rocks around them that can be detected as earthquakes.

Additionally, the volatility of volcanoes and the accompanying earthquakes has been shown to be linked to dike induced stress and the interaction this causes between the magma, rock, and wall of the chamber.

[2] Some notable examples of eruptions preceded by volcano tectonic earthquakes include ones at Nevado del Ruiz (1985), Pinatubo (1991), Unzen (1990), and Cotopaxi (2002).

[2] Other types of seismic activity monitored in relation to volcanoes and their eruptions are long period seismic waves (caused by sudden sporadic movement of magma that had previously not been moving due to a blockage), and harmonic tremor (indicating steady magma movement).

Four types of seismograms , or seismic signatures
Nevado del Ruiz during the 1985 eruption. This eruption was one where seismic activity was monitored in order to determine that an eruption was imminent.