Excitation and Propagation of Lg in Central Eurasia,
SAINT LOUIS UNIV MO DEPT OF EARTH AND ATMOSPHERIC SCIENCES
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Lg spectra from 20 underground nuclear explosions and 52 shallow earthquakes in central Eurasia have been collected at 21 broad band IRIS, CDSN and KNET stations. Using the non-linear method of Xie 1993, we simultaneously invert for Lg source spectral parameters and path-variable Lg Q sub 0 and eta values Lg Q at 1 Hz and its power-law frequency dependence, respectively. The inversions yield Lg seismic moments M sub 0, corner frequencies f sub c for the events, as well as Lg Q sub 0 and eta values for numerous paths in central Eurasia. Grossly speaking, Lg Q and Lg coda Q are similar in central Eurasia, although minor discrepancies exist between a Lg eta and Lg coda eta at large about 2700 km distances, and b Lg Q sub 0 and Lg coda Q sub 0 values in a sub-region northeast of the Lop Nor test site. For both explosions and earthquakes Lg Mo values correlate linearly with the ISC M sub b values, both having slopes slightly greater than 1.0. For the same Lg M sub 0 values, Mb values from explosions tend to be larger than those from earthquakes. Lg M sub 0 tend to scale with f exp -alpha sub c, with a closer to 4 than to 3. Regression analysis over M0 and f sub c values suggest that for the same M sub 0 values, explosions tend to have higher f sub c values. This may form a basis of an explosion discriminant, but the fact the there is a slight overlap among M sub 0 and f sub c values from explosions and those from earthquakes suggests that the use of this discriminant should be used with caution. Applications of the methodology used in this study to other regional phases, such as Pn, may contribute to our understanding of regional wave excitationpropagation by various types of seismic source, and to the evaluation of various discriminants using regional waves.
- Government and Political Science
- Seismic Detection and Detectors
- Nuclear Weapons