Abstract
Earthquakes were associated with volcanic eruptions from ancient times. The volcano Vesuvius occupies a special place in the history of the study of seismic signals associated with volcanic activity. The first observations of volcanic earthquakes showed that the seismic signals originating from volcanic activity had different waveforms. Volcanic eruptions are divided into four types according to the location of their foci, their relationship to the eruptions, and the nature of the earthquake motion. A-type earthquakes originate from the bases of volcanoes or from the depths of about 120 km. These earthquakes take place previous to and during the first stage of eruptive activity and occur in swarms. They are generally less than 6 in magnitude. The hypocenters of B-type earthquakes are limited to an area of about 1 km in radius around the active crater. The hypocenters of these earthquakes are shallower than those of the A-type volcanic earthquakes. Explosion earthquakes are the one, which accompany individual explosive eruptions. The amplitude of these earthquakes is related to the magnitude of the explosive eruptions. Volcanic pulsation or continuous volcanic micro-tremors consists of the surface waves. Volcanic tremor has a form of an irregular sinusoid of rather long duration compared with earthquakes of the same amplitude. Earthquake swarms are generally defined as a sequence of events closely clustered in time and space without a single outstanding shock. Volcano-tectonic earthquakes may occur in all three types of sequences. The two first types of sequences are rare, and they occur prior to flank or fissure eruptions. The swarm sequences are the most common for volcanic earthquakes.
Published Version
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