HR: 1340h
AN: S33A-0292    [Abstracts]
TI: Automated Dispersion Curve Imaging for Seismic Hazard Evaluation Using the Multiple Filter Technique
AU: * Abbott, R E
EM: reabbot@sanda.gov
AF: Sandia National Laboratories Solid Dynamics and Energetic Materials Dept., P.O. Box 5800, Albuquerque, NM 87185-1168 United States
AU: Bartel, L C
EM: lcbarte@sandia.gov
AF: Sandia National Laboratories Geophysics Dept., P.O. Box 5800, Albuquerque, NM 87185-0750 United States
AB: Average shear-wave velocity in the upper 30 meters is a key parameter for seismic hazard calculations. Geologic maps show poor correlation with predicted subsurface velocity, therefore measurements are needed at multiple locations for the area of interest. We present an alternative to existing surface-wave techniques (e.g. SASW, MASW, ReMi) for rapid site assessments. Data collection consists of an active source (hammer and plate, weight drop, etc.) recorded on an arbitrary array of seismic sensors. After populating the raw data with the source-receiver geometry, the technique will find the surface-wave group-velocity dispersion curve for the site without user interaction. The processing consists of applying narrow bandpass filters for the frequencies of interest, followed by the Hilbert transform to find the instantaneous amplitude of the waveform (multiple filter technique). Automated picks are made of the local maxima of the instantaneous amplitude. Generally, between two and four picks are made, so that higher modes are included if present in the data. The picks for all sources and receivers are then sorted in velocity-frequency or slowness-frequency bins and plotted at once. The group-velocity dispersion curve is readily apparent in this plot, and can be used for subsequent modeling. Because this is not a wavefield transformation technique, the dispersion is shown free of truncation and aliasing artifacts. We demonstrate the technique with data from an experiment near Albuquerque, New Mexico.
DE: 3270 Time series analysis (1872, 4277, 4475)
DE: 7255 Surface waves and free oscillations
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: Fall Meeting 2005