Hystory of Ischian Earthquakes

Abstract

The earliest sources on the seismicity of the island of Ischia date back to the Greek colonization of the Island in the eighth century BC. Until the eruption of 1302, seismicity was widespread across the whole Island, while thereafter it was mainly concentrated in its northern part, at the foot of the Monte Epomeo massif. One of the characteristics of earthquakes on Ischia is that they occur very near the surface, since at depths of more than 3 km, due to their high temperatures (> 400 °C), the rock has a ductile as opposed to a fragile behavior, and hence do not fracture and do not gene rate earthquakes. Earthquakes are due to the moving of adjacent blocks separated by a surface of discontinuity known as a fault, along which the relative movement of the two blocks occurs when tectonic forces become stronger than the friction that impeded their movement. After an earthquake, the system needs to reload for the friction to be again overcome and for another earthquake to be thus generated.