Routine analysis for seismic monitoring of eastern Sicily (Italy)

Abstract

Eastern Sicily is one of the most high seismic and volcanic risk areas in Italy. The systematic monitoring of seismic activity in this region is carried out by means of a permanent local network, managed by the Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Catania (INGV-CT). The monitoring is performed: on-line by means of automatic systems designed to detect and elaborate the earthquakes and volcanic tremor, while off-line thanks to an expert scientific staff. Skilled ”analysts” daily recognize, analyse and storage all seismic events which occur in the Eastern Sicily, providing accurate information on the time evolution of earthquake activity recorded within the seismic network. In particular, the studied area encompasses four different geodynamic domines: two volcanic areas (Etna, Aeolian Island) and two tectonic ones (Hyblean Plateau and Peloritain Mountains). The good quality of earthquakes locations, the precise and the careful storage of the data, are a fundamental basis for further and important seismological studies. In detail, the scientific staff carry out, with high precision and regularity, the following main tasks: - daily counting of the earthquakes that is possible to recognize on seismograms of continuous recordings; calculation of the duration magnitude and the cumulative seismic strain release; - earthquakes location by using Winsuds software to calculate the main hypocentral parameters stored in catalogues that can be consulted in http://www.ct.ingv.it/Sismologia/analisti/default.asp - calculation of local magnitude for all the localized earthquakes with Matlab code; - waveforms, P and S-wave readings polarities and Hypoellipse output files are stored in appropriate directories inside a Databank; the Database mainly contains the “local” events recorded within the areas of coverage and some events recorded outside the network but in adjoining areas (e.g. southern Calabria, Ionian Sea, Thyrrenian Sea); - information on the daily number of explosion-quakes, VLP and landslides recorded at Stromboli volcano and on the number of very local earthquakes recorded in proximity of La Fossa of Vulcano island; - computation of focal plane solutions using the FPFIT algorithm with the aim to evaluate nodal planes and orientation of P and T axes for earthquakes with Md  3.0. Moreover, during the main eruptive events the scientific staff, in order to alert regional and national Civil Protection authorities, furnish a detailed analysis of seismic activity (parameters of earthquake locations, epicentral maps and cross sections, focal mechanisms, seismic strain release, earthquake rate, etc…) in real time or near real time.