Volcanic Seismicity

Volcano seismology is the study of earthquakes of volcanic origin as well as of velocity structure, attenuation, and other physical properties of the Earth materials that affect the passage of seismic waves at volcanoes. Volcanic earthquakes may be defined as earthquakes that occur at or near volcanoes, generally within 15 km, or that are related to volcanic processes. Volcanoes are places where heat and mobile fluids are concentrated, so the number of earthquakes per unit time is high when compared with normal crust. Most volcanic earthquakes take place at shallower depths (1–9 km) than tectonic earthquakes on typical faults (generally to depths of about 15 km in the crust; as deep as 700 km in subduction zones). Volcanic events also differ in their patterns of occurrence: they often occur in swarms, which are groups of many small events with similar magnitudes and locations. This is in contrast to the typical mainshock–aftershock sequences characteristic of tectonic earthquakes. Volcanoes produce different types of earthquakes that are thought to represent different physical processes