Abstract

The coda Q of the early coda of shear waves was determined from a network of seismic stations deployed in the Mono Craters area during the summer of 1982. Coda amplitudes determined from a moving window analysis were fit to single scattering theory with an L1 norm for center frequencies from 1.5 to 12.0 Hz.

We find that station-to-station variations in coda Q, observed for frequencies between 6 and 12 Hz, are well correlated with near-site geology. Coda Q for stations on crystalline rocks is larger and more frequency dependent than for stations sited on Bishop Tuff adjacent to Mono Craters. Coda Q from sites on Bishop Tuff away from Mono Craters is still lower and less frequency dependent. These observations suggest that site effects dominate the early coda in the Mono Craters region, and that the single scattering model is inappropriate. The mechanisms generating these site effects are inferred to be: 1) multiple scattering from resonant structures such as sedimentary basins, volcanic edifices, variable basement topography, and surface topography; and 2) near-site attenuation.

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