GNGTS 2013 - Atti del 32° Convegno Nazionale

The corner frequency estima- tion appears quite stable. The relationship between seismic moment and corner frequency is approximately . We calculate stress drop using the following equation (Madariaga, 1976): The values range between 0.1 and 1.8 MPa (Fig. 3), which are within the bounds general- ly found for crustal earthquakes (10 4 Pa < Δσ < 10 8 Pa, e.g. Hanks, 1977; Kanamori, 1994). The ob- tained values of stress drop are within the range reported by sev- eral authors for the Emilia seismic sequence (Malagnini et al. , 2012; Castro et al. , 2013). We have also compared, wherever possible, our magnitude estimation with the ones obtained by other Authors (Malagnini et al. , 2012; Pondrel- li et al. 2012; Saraò et al. , 2012; Scognamilio et al. , 2012). The agreement is quite fair especially for the major events (MW > 5). The differences for some values are due to different initial assump- tions to compute moment magni- tude, such as, e.g., velocity model, epicentral distance and frequency range. The results obtained repre- sent an important validation for our real-time procedure proving that it is robust and reliable. This real-time automatic procedure is now routinely used at DMG and at the Department of Civil De- fense (DPC) in Rome for a rapid determination of earthquake pa- rameters. Acknowledgements. We would like to thank the Italian Civil Protection for kindly providing us part of the seismic data used in this research. Part of his work was financially supported by the S.H.A.R.M. Project of the Area Science Park of Trieste: “Tomografia crostale per la valutazione e mitigazione del rischio sismico”. This study was partially supported also by Project S1 of the Instituto Nazionale di Geofisica e Vulcanologia (INGV) (2012-2013): ”Miglioramento delle conoscenze per la definizione del potenziale sismogenetico”. Fig. 2 – Corner frequency versus seismic moment. The relationship between seismic moment and corner frequency is approximately . Fig. 3 – Stress drop values computed following Madariaga (1976). 61 GNGTS 2013 S essione 1.1