Effect of Transient Seismic Noise on Estimates of h/v Spectral Ratios

The horizontal-to-vertical (H/V) spectral ratio of seismic noise has be- come a widely used tool in microzonation over the last decade. However, attempts to provide standards for seismic-noise analysis have only recently been made. One point often debated is whether only the stationary part of the recorded signal must be used or also the transients. Until now, no systematic analysis has been carried out to clarify this point. In this study, we compare H/V spectral ratios obtained using stationary noise with those calculated without any a priori selection of the signal. Results show that transients have no (or very little) effect on the H/V ratio. Further- more, we filter the seismograms using a wavelet-packet transform method, to perform H/V spectral-ratio calculations for only the transients. Results show a large variability in the H/V shape that we explain, by means of numerical simulations, as being due to source type and distance from the receiver relative to the thickness of the sedi- mentary cover.

[1]  Rongjiang Wang,et al.  A simple orthonormalization method for stable and efficient computation of Green's functions , 1999, Bulletin of the Seismological Society of America.

[2]  Mitsuo Nogoshi,et al.  On the Amplitude Characteristics of Microtremor (Part 2) , 1971 .

[3]  Francisco J. Chávez-García,et al.  Site effect evaluation using spectral ratios with only one station , 1993, Bulletin of the Seismological Society of America.

[4]  Maria Rosaria Gallipoli,et al.  The Stability of the Horizontal-to-Vertical Spectral Ratio of Triggered Noise and Earthquake Recordings , 2003 .

[5]  Marco Mucciarelli,et al.  RELIABILITY AND APPLICABILITY OF NAKAMURA'S TECHNIQUE USING MICROTREMORS: AN EXPERIMENTAL APPROACH , 1998 .

[6]  Walter H. F. Smith,et al.  Free software helps map and display data , 1991 .

[7]  Peter Bormann,et al.  ASSESSMENT OF THE NATURAL FREQUENCY OF THE SEDIMENTARY COVER IN THE COLOGNE AREA (GERMANY) USING NOISE MEASUREMENTS , 2001 .

[8]  T. Ohmachi,et al.  Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors. , 1997 .

[9]  Mitsuo Nogoshi,et al.  On the Propagation Characteristics of Microtremor , 1970 .

[10]  Masanori Horike,et al.  Comparison of Site Response Characteristics Inferred from Microtremors and Earthquake Shear Waves , 2001 .

[11]  Francisco J. Chávez-García,et al.  Are microtremors useful in site response evaluation , 1994 .

[12]  Mitsuo Nogoshi,et al.  On the Amplitude Characteristics of Microtremor (Part 1) , 1970 .

[13]  Daniel E. McNamara,et al.  Ambient Noise Levels in the Continental United States , 2004 .

[14]  Maria Rosaria Gallipoli,et al.  The influence of wind on measurements of seismic noise , 2005 .

[15]  Stratos Zacharopoulos,et al.  Guidelines for the implementation of the H/V spectral ratio technique on ambient vibrations measurements, processing and interpretation , 2004 .

[16]  J. J. Giner,et al.  De-Noising of Short-Period Seismograms by Wavelet Packet Transform , 2003 .

[17]  Peter Bormann,et al.  Assessment of the stability of H/V spectral ratios from ambient noise and comparison with earthquake data in the Cologne area (Germany) , 2004 .

[18]  Y Nakamura,et al.  A METHOD FOR DYNAMIC CHARACTERISTICS ESTIMATION OF SUBSURFACE USING MICROTREMOR ON THE GROUND SURFACE , 1989 .

[19]  Dario Albarello,et al.  Statistical Analysis of Noise Horizontal-to-Vertical Spectral Ratios (HVSR) , 2005 .

[20]  Martin J. Siegert,et al.  EOS Trans. AGU , 2003 .

[21]  Edward H. Field,et al.  The theoretical response of sedimentary layers to ambient seismic noise , 1993 .