SOURCE SPECTRA AND SITE-RESPONSE ESTIMATES USING THE CODA OF LG WAYESIN WESTERN-EUROPE

Source spectra are investigated by using regional events recorded by t he LDG French short-period seismic network. Empirical relations descri bing the Lg coda envelope allow vs to separate source, site and propag ation effects. 28 events recorded by 14 stations of the LDG network ar e selected for this study. Source spectra and site-response are determ ined in the frequency-band of 1-16 Hz. A Lg-coda magnitude can be defi ned from these source spectra. Magnitudes obtained by this technique a re strongly correlated to local magnitudes given by the LDG bulletin b ut the standard deviation is reduced by a factor 3. Other parameters s uch as site-response, corner-frequency and coda Q are determined very accurately.