HR: 1340h
AN: S33A-0288    [Abstracts]
TI: Application Of The Wavelet Packet Transform For Selecting Transient Seismic Noise And Study Of Its Effect On Estimates Of The H/V Spectral Ratio
AU: * Galiana-Merino, J
EM: juanjo@dfists.ua.es
AF: Dpto. Fisica, Ingenieria de Sistemas y Teoria de la Senyal, Universidad de Alicante, Carretera de San Vicente del Raspeig s/n, San Vicente del Raspeig, Alicante, 03690 Spain
AU: Parolai, S
EM: parolai@gfz-potsdam.de
AF: GeoForschungsZentrum - Potsdam, Telegrafenberg , Potsdam, 14473 Germany
AB: The Horizontal-to-Vertical (H/V) spectral ratio of seismic noise has become a widely used tool in microzonation, although it has not yet been clearly established whether or not only the stationary part of the recorded signal may be used. In fact, while some studies have suggested the use of only stationary signals others have shown that including transients may improve the results. In this study, we have employed a filtering method based on the wavelet packet transform for removing the stationary part of the noise recordings in the frequency band of interest for the H/V spectral ratio. In this way, we have obtained filtered seismograms with only transients, which have been used for performing the H/V spectral ratio calculation. Moreover, we have also calculated the H/V spectral ratio selecting only stationary noise windows from the seismograms and without making any a priori selection on them. Finally, we have compared the results and analysed the influence of transient noise on the shape of the H/V spectral ratio. The analysis has been carried out on noise recordings collected at 7 stations installed in the Cologne-Bonn region (Germany). Results show that the H/V spectral ratios calculated using only stationary noise do not significantly differ from those obtained without performing any data selection, independent of the site resonance frequency and of the frequency content of the transient. On the contrary, H/V spectral ratios obtained using only transients show a large variability that may be attributed to the kind of source and the source to receiver distance. These results indicate that the effect of transient noise is negligible when the H/V spectral ratios are calculated without performing any data selection, making the H/V spectral ratio technique more attractive for urban area measurements.
DE: 7290 Computational seismology
SC: Seismology [S]
MN: Fall Meeting 2005