Update of the Italian Seismic Catalog (2003-2007) Catalogo della Sismicità Italiana CSI v2.0

Abstract

Earthquake catalogues are the basic tools that furnish parametric data for seismic hazard evaluation, studies on evolution of seismic sequences and earthquake occurrence. The INGV seismic network covers a large part of the italian region and it is complemented by several regional permanent network handled by other institutions. CSI results from the combination of INGV seismic bulletin with bulletins produced by other institutions. To update CSI from previous release to version 2.0 we collected seismic bulletins sent to INGV from, at present, 12 institutions managing permanent seismic networks during 2003-2007. Procedures to convert different file formats to PHS format as input files of Hypoellipse program have been setup that also perform preliminary checks on possible errors. To correctly merge different seismic bulletins it is mandatory to have a strict control on phase associations. To do this, additional procedures to identify earthquakes external to the interest area and wrong associations of different earthquakes based on geographic control network associations and stations' residuals after event location have been produced. About 35,000 eartquakes, a mean value of ~6600 earthquakes per year, with more than 600.000 P-phase arrivals and more then 250,000 S-phase arrivals have been collected and located with Hypoellipse. To enhance final locations quality we applied a multiple location approach and then selected the best among several calculated hypocentres for each event. Location criteria are based on the use of two different weighting schemes for stations' distance combined with several reference regional 1D velocity models. Native Ml Magnitudes from 2003 to 2007 are retrieved and then associated to the corresponding event from INGV bulletin. When native Ml is not available, Ml based on regression law by Castello et al. 2007, is attributed. The update of CSI catalog, also due to the strong improvement of the INGV seismic network between 2005 and present, offers a more complete image of the Italian seismicity and a new important reference for further studies on the evolution of this region and earthquake occurrence.