(4)Other earthquakes
Forces operate locally in the shallow sections of rock mass on the periphery of a volcano. Small and medium size earthquakes frequently accompany volcanic activity. On rare occasions, large earthquake on the order of M 7 occur. One example was the 1914 earthquake at Sakurajima (M 7.1) that accompanied large eruptions on Sakurajima Volcano. Earthquake swarms are sometimes seen on the periphery of volcanoes. For example, the swarm activity in the open sea east of the Izu Peninsula is thought to be related to volcanic activity.