Effects of a descending lithospheric slab on yield estimates of Aleutian nuclear tests. Incorporation of velocity gradients in the synthesis of complete seismograms by the locked-mode method
The locked mode method of synthesizing complete regional seismograms (Harvey, 1981) was modified to include the Langer uniform asymptotic approximation to vertical wave-functions within layers having linear vertical velocity gradients. Good agreement is obtained in gradient models between synthetics computed using the Langer-locked mode method, the colocation method, and the conventional locked mode method in models parameterized by thin homogeneous layers. Errors in calculated displacement introduced by the use of the Langer approximation remain less than several percent for wavelengths lambda < or = 0.2V/nabla operator V. Whenever it is necessary to represent gradients accurately, the Langer-locked mode method is computationally more efficient than the locked mode method using thin homogeneous layers. By reducing the number of parameters needed to describe an Earth model, the Langer-locked method will also simplify the inverse problem of determining structure using observed and synthetic regional seismograms. Test calculations of regional seismograms confirm that the Pn and Sn phases are strongly affected by the magnitude of the velocity gradients beneath the Moho, but that Lg is only weakly affected by the details of crustal layering.
- Research Organization:
- Connecticut Univ., Storrs, CT (USA). Dept. of Geology and Geophysics
- OSTI ID:
- 6111281
- Report Number(s):
- AD-A-227423/1/XAB; SCIENTIFIC-3; CNN: F19628-88-K-0010
- Country of Publication:
- United States
- Language:
- English
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NUCLEAR EXPLOSIONS
YIELDS
UNDERGROUND EXPLOSIONS
ALEUTIAN ISLANDS
CALCULATION METHODS
DATA ANALYSIS
DISPLACEMENT RATES
EARTH CRUST
EVALUATION
MATHEMATICAL MODELS
MATHEMATICS
ORIENTATION
SEISMIC EFFECTS
SEISMIC WAVES
TESTING
WAVE PROPAGATION
EXPLOSIONS
ISLANDS
450200* - Military Technology
Weaponry
& National Defense- Nuclear Explosions & Explosives