The first stations of the Friuli Venezia Giulia (
In November 1999 the collaboration between DST and ENEL ended due to the internal reorganization of the ENEL group. As a consequence, at the end of 1999, the configuration of the network changed. New more appropriate free-field sites were found near the original ones. RAF is today configured to record accelerations at several important sites in the seismic area of Friuli Venezia Giulia (FVG) and near its borders with
The RAF stations allow real-time or near-real-time data transmission to the seismological datacenters and to the Friuli Venezia Giulia Direction of the Civil Defence (FVG-DPC) headquarters. As a consequence the accelerations recorded at each site are immediately available after the earthquake occurrence.
In the year 2000, DST and the FVG-DPC signed an agreement for the RAF management and its use, not only for scientific studies, but also for civil defence purposes, like the prompt estimate after an earthquake occurrence of the related damage level and its areal extent, the emergency management, the reconstruction planning, and the validation and updating of seismic hazard maps. Moreover, RAF recordings are used also for civil defence prevention purposes. This is accomplished through the computation of possible ground-shaking scenarios, studies of seismic source properties, site effects estimates and microzonation analyses. In particular, for what concerns the estimation of site effects, some of the RAF accelerometric stations have been installed at sites characterized by peculiar Quaternary geological features that produce significant amplifications of seismic signals.
In the year 2000, when the RAF geometry has been completely revised (Map), the seismological instrumentation was upgraded. The newly installed high dynamic (>120 db) instrumentation is formed by three-component feedback digital broadband accelerometers coupled with 18 or 24 bits acquisition systems (Table). The poles and zeros of the sensor response curves are reported in Figure 4. Some stations belonging to RAF are also stations of the Northeast Italy Broadband Network, equipped also with broadband sensors, mainly Streckeisen STS-2.
Furthermore, classical earthquake parameters, like hypocentral coordinates and magnitude are immediately available at the FVG-DPC headquarters. The occurrence of an earthquake is announced to the FVG-DPC operators by SMS, e-mail and automatically generated WEB pages.
Since 2003 an agreement between the National Civil Defence (DPC) and the Regional Civil Protection (FVG-PC) has been signed in order to co-ordinate and integrate on the Friuli Venezia Giulia territory the National Accelerometric Network (RAN) and the Friuli Venezia Giulia Accelerometric Network (RAF). This co-operation will lead to the installation of new RAN accelerometric stations in the area and, in particular, will allow to automatically send RAN and RAF data to the DPC headquarters in Rome and to DST, through the FVG-PC data center. As FVG-PC consultant for the strong ground motion issue (network, data, studies), the DST collaborates to the sites selection and to the management of the new RAN stations. DST has recently performed detailed noise measurements in order to give a local geological classification of the recording sites.
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, by the network, are collected and exchanged through the datacenters.
An automatic procedure has been developed by DST to extract in real-time the ground motion parameters (PGA, PGV, PSA03, PSA10, PSA30, Arias and Housner intensities) and to exchange these data with other partners of the Project INGV-DPC S3. The ground motion parameters are used also to generate regional real time ShakeMaps, to compute regional weak motion GMPEs and possible ground-shaking scenarios. The collected waveforms are also used to study the physics of the seismic source, to estimate site effects and to perform microzonation analyses.
At DST an accelerometric database with RAF data as of today about 700 digital 3-component records, related to about 400 events - has been maintained since 1993.