Upper mantle structure of northwestern Eurasia
Long- and short-period WWSSN seismograms from nuclear explosions in the Union of Soviet Socialist Republics are incorporated with apparent velocity observations to derive an upper mantle model for northwest Eurasia. The compressional waves from these explosions have several distinctive features that provide important new information about the character of the upper mantle in the region. The seismograms from 9/sup 0/ to 13/sup 0/ exhibit impulsive first arrivals P/sub n/, implying a smooth, positive velocity gradient between depths of 60 and 150 km. There is a consistent pulse arriving about 2s after P/sub n/ at the ranges from 13/sup 0/ to 17/sup 0/, and at larger ranges there are distinct reflections from the two major discontinuities of the mantle. Synthetic seismograms displaying these features indicate a model that correlates with other velocity models from around the world, with a distinctive lid and low-velocity zone. The arrival following P/sub n/ is modeled by positioning a low-velocity zone between 150 and 200 km. The model is relatively smooth from a depth of 200 km down to 420 km, where a 5% jump in velocity produces a triplication from 15/sup 0/ to 23/sup 0/. The observations from 21/sup 0/ to 26/sup 0/ clearly show another discontinuity at a depth of 675 km with a 4% change in velocity. These results suggest that stable continental regions may have a shadow zone that extends to beyond 17/sup 0/. Below 250 km depth there is no distinguishable difference between the model proposed for northwest Eurasia and models derived for the United States.
- Research Organization:
- Seismological Laboratory, California Institute of Technology, Pasadena, California 91125
- OSTI ID:
- 7064136
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 85:B13
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ASIA
GEOLOGIC MODELS
EARTH MANTLE
EUROPE
NUCLEAR EXPLOSIONS
SEISMIC EFFECTS
CONTINENTAL CRUST
EARTHQUAKES
GEOLOGIC STRUCTURES
SEISMIC P WAVES
UNDERGROUND EXPLOSIONS
USSR
WAVE PROPAGATION
EARTH CRUST
EASTERN EUROPE
EXPLOSIONS
SEISMIC EVENTS
SEISMIC WAVES
580201* - Geophysics- Seismology & Tectonics- (1980-1989)