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Published February 1981 | Published
Journal Article Open

Seismic source functions and attenuation from local and teleseismic observations of the NTS events Jorum and Handley


Several strong-motion seismograms recorded at 8 km from a large nuclear test at Pahute Mesa, Nevada Test Site, are modeled using the Cagniard-de Hoop technique. The ratio of vertical to radial motions suggest that the peak values are produced by ray paths that penetrated to a depth several kilometers below the source. A homogeneous layered Earth model with velocity increasing with depth was used in the modeling of the velocity time histories. The upper portion of the velocity model was determined by averaging bore-hole data and the lower portion was obtained from regional refraction measurements. Assuming a modified Haskell (1967) source representation, ψ(t) = ψ_o[1 - e^(-Kt)(1 + Kt (Kt)^2/2 - B(Kt)^3)] we obtain a range of source descriptions with ψ_o varying with K and B, ψ_o (K,B). The range of source models for Jorum are ψ_o (5, 1) = 3.1, ψ_o (5, 2) = 1.7, and ψ_o (5, 3) = 1.2 times 10^(11) cm^3, respectively. Given an explosion source description, it is a straightforward task to determine the teleseismic attenuation from WWSSN observations. From both the short- and long-period observations from these events, an average t^* of 1.3 is obtained for compressional waves of a dominant 1-sec period. This estimate is insensitive to the range of K and B obtained from the near-field modeling.

Additional Information

© 1981, by the Seismological Society of America. Manuscript received April 12, 1980. We thank Robert S. Hart and Jim Dewey who critically reviewed the manuscript. This research was supported by the Advanced Research Projects Agency of the Department of Defense and was monitored by the Air Force Technical Applications Center under Contract F08606-79-C-0009, Sierra Geophysics Report SGI-R-79-006.

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