FRIULI-VENEZIA GIULIA 

ACCELEROMETRIC NETWORK

RAF

RAF DATABASE 

A database containing the waveform of the events recorded by RAF from 1993 is available at DST.

Diagrams

Events Events present in the Friuli Accelerometric Network database (1993-2003).

 

The Friuli seismic area is characterised mainly by N-S compressional stress as due to the interaction between the Adria microplate and the Eurasian plate. The seismic activity is of relatively low intensity. The return period of strong earthquakes with magnitude greater then 6 is about 40 years, and the return period of earthquakes with magnitude greater then 5 is about 7 years (CCI96 Italian catalogue, Peresan et al., 1997). In the first four years of network activity, about 80 low-magnitude events (between 1.5 and 4.0) have been recorded.

 

Flow chart of the data processing.

 

The original data recorded by the different instruments are pre-processed at DST and their format is changed to the standard GSE format, which contains all the information extracted from the station history and instrument response databases and from the earthquake catalogue. The data are, then, processed and the corrected signals, the Fourier spectra and the response spectra, are computed and added to the database. At the end graphic procedures are used to plot the data and create the annual report of the network (Costa et al., 1996a, 1996b, 1997, 1998a, 1998b). Other procedures extract from the database some selected engineering parameters of ground-motion (PGA, PGV, PGD, Energy, Arias intensity, etc.).

In the annual report the corrected signals are given together with the computed Fourier spectra and response. The characteristics of the recording station, the parameters of the related seismic event, and the map with the epicentre and the station are also reported.

 

Example of the RAF report.

 

In the database and in the annual report, all waveforms are shown that correspond to an event in the area of the network localised by the local OGS seismic network. Waveforms of some particularly interesting events not fulfilling these conditions (e.g. swarms, etc.), are added to the database. The database contains also the waveforms recorded by the stations of PRAD and MOG during the Umbria event of September 1997, Ml=5.9 (distance about 300 km).

A large number of events  (more than 278, and mostly of small magnitude) have been recorded by the RAF during its years of activity. A special issue of the bulletin containing the waveforms recorded during the Bovec (Slovenia) April 12, 1998 Ml=5.6 event, about 50 km far from the network, has been published. The corresponding computed velocities and displacements are reported as well. The recordings corresponding to damaging accelerations for buildings are related to the 1998 Bovec-Krn event. The closest t stations (around 30 km) to the mainshock epicenter measured around  30 cm/s2 PGA. During the recent february, 14th 2002 earthquake (Ml 4.9), the largest so far recorded PGAs (120 cm/s2) have been obtained by a few stations located very close to the epicenter (around 5 km). These data are particularly important for site effects studies carried out in the Gemona town.

In the RAF database we also find 2 accelerograms related to the 1998 Umbria earthquake (Ml 5.9) which occurred more than 300 km far from the RAF stations. Moreover, 3 accelerograms related to the 2002 Merano earthquake (Md 5.2, distance around 170 km) are available.

At the DST WWW address www.dst.units.it a page describes the network is and allows to request the available data and reports directly through the Internet.

 

Available Data (1993-2003)

  raf@dst.unts.it