Mw estimation and ShakeMaps generation using real-time accelerometric waveforms recorded in the Southeastern Alps

The Friuli Venezia Giulia Accelerometric Network (RAF) is configured to record accelerations at several important sites in the seismic area of Friuli Venezia Giulia and near its borders with Slovenia and Austria. The network geometry is built up taking into account also other seismological agencies and networks operating in Friuli Venezia Giulia (OGS) as well as in Austria (ZAMG) and Slovenia (ARSO). The data recorded in real-time, or quasi real-time, are collected and exchanged through the datacenters by the Antelope software. Antelope also analyzes and stores the collected waveforms in a database containing the signals recorded by this network and by the integrated transfrontier seismic network. An automatic procedure has been developed to extract in real-time the ground motion parameters that are used also to generate regional ShakeMaps for the SE Alps within five minutes of the earthquake occurrence. The “ShakeMap” software has been regionally calibrated by adopting a specific near-surface geological classification, different GMPEs for weak and strong motion, and the relationship proposed by Faccioli and Cauzzi (2006) to compute the instrumental intensity. The model is validated by comparing the observed intensity maps data with the instrumental intensities derived from the related scenarios calculated for three important past seismic events in the studied area (Cansiglio 1936, Friuli 1976, Bovec 1998). The computation of the intensity misfit value gives satisfactory results. To improve the ShakeMap generation an automatic method is implemented to estimate in real time the seismic moment, moment magnitude and corner frequency from broad-band and accelerometric data. The procedure has two steps: the first one consists in interfacing with the Antelope system from where waveforms are retrieved. The second step consists in estimating the seismic moment and the corner frequency following Andrews method (1986). At the end the results are stored in a database table. The procedure is tested with the recordings of some strong earthquakes: Carnia 2002 (Mw=4.9), Bovec 2004 (Mw=5.1), Parma 2008 (Mw=5.4) and Aquila 2009 (Mw=6.1), some its aftershock and those of some minor events occurred in the SE Alps. The results are posted automatically on the department web pages (www.dst.units.it/RAF06).