The epicentral areas of volcanic earthquakes and their volcanotectonic significance

Abstract

Volcanic earthquakes occur in swarms and their foci are distributed around the volcanic edifice. The size of the epicentral area and the position of the largest volcanic earthquakes in the eruptive sequences are studied. Eight large volcanic eruptions from different parts of the world were chosen for study. The area of occurrence of small volcanic earthquakes varies strongly for different volcanoes, and the largest volcanic earthquakes occur up to 10-15 km from the eruptive center. Both area and distance between the eruptive center and the position of the largest earthquake are inversely correlated with crustal thickness. The area of fractured rocks between the magma chamber and the surface may be larger in the vertical than the horizontal dimension for continental volcanoes, and conversely for oceanic volcanoes.