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I. N. Gupta R. R. Blandford R. A. Wagner J. A. Burnetti T. W. McElfresh 《Geophysical Journal International》1985,83(2):541-553
Summary. Spectral analysis of P and P coda from NTS explosions recorded at NORSAR shows that magnitudes based on spectral integration of P coda provide a significantly more precise measure of yield than those based on the initial P . Coda amplitudes and spectra are considerably less sensitive to near-source variations than the direct P . A plot of P -coda magnitude, after correcting for the effects of attenuation in the upper mantle and the source spectrum based on knowledge of approximate yield or mb , versus log yield appears to have a slope of unity. This implies that P coda from several stations (with different but known t * values) can be combined to improve the yield determinations further. Single station P coda from Soviet explosions can also be used to determine relative yields that appear to be at least as precise as those from Lg based on a network of stations. 相似文献
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K. A. Berteussen 《Pure and Applied Geophysics》1977,115(3):707-719
Using simulated data, it is demonstrated that one may estimate the body wave velocity in the crust by measuring the angle of incidence ofP-waves provided only the very first part of the signal is used. This angle has been measured for a set ofP-waves at the NORSAR long period instrument sites. Combining these observations with measurements of apparent velocities, we find that the data indicates a crust velocity of 6.1±0.4 km/sec. While it is somewhat uncertain to what depth the value is representative, the observations are in obvious disagreement with previous authors who concluded that long periodP-waves were not affected by the earth's crust. Because of difficulties in separating the effects of real velocity variations from measurement errors, the details of the observedP-wave variation across the array are difficult to interpret. The consistent behavior of the data does, however, indicate that variations of approximately 3% must exist in the crustalP-wave velocity across the array. 相似文献
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