Yield Estimation from Spectral Amplitudes of Direct P and P Coda Recorded by the Wake Island Deep Ocean Hydrophone Array

摘要

Spectral amplitudes of direct P and P coda between 0.5 and 6 Hz were measured for 14 Eastern Kazakh test explosions using 8 hydrophones of the Wake Island Array(WIA). A new model for these data was developed to estimate relative yields of those explosions. Each log spectral amplitude is considered to be the sum of four parameters and an error term. The 3 frequency-dependent parameters represent: 1) the average Eastern Kazakh spectrum at the WIA; 2) the spectral shape characteristics unique to each event; and 3) the station or hydrophone corrections. The fourth parameter represents relative yield. A total of 346 parameter, were needed to model all 901 spectral amplitudes that were measured, and first-order linear regression technique were used to invert the data for these parameters. Standard deviations of the computed relative yields are very small. Deviations between the relative yields and their corresponding relative NEIS body-wave magnitudes, however, are larger. This difference is interpreted to be an indicator of the level of inhomogeneity in the worldwide pattern of energy radiated from Eastern Kazakh tests. It is proposed that the yield of a large explosion might be disguised by siting the explosion at a location that selectively defocuses energy towards continents where most seismic stations are located. Reprints. (EDC)