In order to evaluate the frequency dependence of site effects, the joint analysis of the standard spectral ratio technique with a sonogram approach is proposed ( Joint Analysis of Sonogram and Standard Spectral Ratio). Two tools are suggested: the enhanced sonograms and the differential sonograms. In particular, the local geology effects are investigated by considering both the amplification of the seismic signals and their prolongation. Tests carried out on synthetic signals show the capability of the sonogram approach to evaluate the frequency-dependent lengthening of the seismic signal. The JASSSR is applied to data recorded by a dense local network deployed during the Umbria-Marche seismic sequence of 1997 and to data recorded in the Volvi Test site (Euroseistest, Greece). The results show that using the JASSSR gives a more complete overview of the effects of local geology on seismic ground motion than may be obtained by using the Standard Spectral Ratio alone. In particular, the effect of secondary arrivals, both on the amplitude and on the lengthening of the seismic ground motion, can be pointed out. In addition, the characteristic frequency of these arrivals can be evaluated.
Evaluation of site effects by means of Joint Analysis of Sonogram and Standard Spectral Ratio (JASSSR)
Parolai S;
2003-01-01
Abstract
In order to evaluate the frequency dependence of site effects, the joint analysis of the standard spectral ratio technique with a sonogram approach is proposed ( Joint Analysis of Sonogram and Standard Spectral Ratio). Two tools are suggested: the enhanced sonograms and the differential sonograms. In particular, the local geology effects are investigated by considering both the amplification of the seismic signals and their prolongation. Tests carried out on synthetic signals show the capability of the sonogram approach to evaluate the frequency-dependent lengthening of the seismic signal. The JASSSR is applied to data recorded by a dense local network deployed during the Umbria-Marche seismic sequence of 1997 and to data recorded in the Volvi Test site (Euroseistest, Greece). The results show that using the JASSSR gives a more complete overview of the effects of local geology on seismic ground motion than may be obtained by using the Standard Spectral Ratio alone. In particular, the effect of secondary arrivals, both on the amplitude and on the lengthening of the seismic ground motion, can be pointed out. In addition, the characteristic frequency of these arrivals can be evaluated.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
