Crustal structure and seismicity of southern Tyrrhenian basin

Abstract

In this paper all the travel-time data from crustal earthquakes that occurred in the period 1978–1991 along the southern Tyrrhenian sea have been re-examined. In particular, 410 local earthquakes recorded at a minimum number of seven seismic stations and 52 shots fired on sea have been utilized to infer a tomographic image of the velocity model beneath a region located in the domain 37°41′–39°10′N and 14°10′–16°44′E. These earthquakes are selected from a database containing about 1000 local earthquakes. The results from the inversion of about 9000 travel-times confirm the strong lateral variations of the velocity model relative to compressional and shear waves. Below the volcanic center of the Aeolian Islands, in the upper crust, several low velocity bodies are found, in agreement with features inferred from seismicity and other geophysical data. The 3-D velocity images also show a thickening of the crust from the center of the Tyrrhenian sea towards the coasts of Sicily and Calabria. Finally hypocenter locations derived from inversion, which appear to be significantly less scattered than using 1-D velocity models, help to identify with some accuracy two notable fault systems of the southern Tyrrhenian basin.