Microtremor site analysis study at Beatty, Nevada

Abstract

Current microzonation mapping procedures often call for the generation of complicated mathematical ground-motion models. These models require that expensive geophysical and geological surveys be performed to gather input information. A more desirable method of estimating ground motions would be to measure these effects directly. Microtremor analysis procedures provide such a direct method. Microtremor data were collected at several sites at Beatty, Nevada, and compared to nuclear event and mathematical model ground-motion spectra. The frequency at which peak amplitudes occurred on all spectra agreed. These frequencies appear at the resonance frequency of the surface layer when stimulated by compressional waves. Results of this experiment add validity to the use of microtremors in microzonation studies.

Site response on seismic motion in the Granada Basin (southern Spain) based on microtremor measurements

“…At sites with no significant local site response (bedrock), the ground velocity spectrum is approximately flat (white noise) over a wide frequency range, while at sites where the sediments and soils dominate the response, the spectrum of microtremors contains peaks that may provide information of the local site response. This feature has been used in microzonation studies (Kanai and Tanaka, 1961;Katz, 1976;Katz and Bellon, 1978;Ohta et al, 1978;Kobayashi et al, 1987a, b;Lermo et al, 1988;Seo et al, 1990;Morales et al, 1991b).…”