P-Wave Velocities in the Upper Mantle beneath Platforms.

Autor: Gordienko, V. V., Gordienko, L. Ya.
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Zdroj: Izvestiya, Atmospheric & Oceanic Physics; Dec2021, Vol. 57 Issue 7, p695-702, 8p
Abstrakt: This study of the velocity profile of the upper mantle beneath continental platforms finalizes our efforts to analyze one-dimensional velocity models for continental and oceanic regions with all types of endogenous regimes. The platform regions are characterized by specific features that distinguish them from the regions with other geological history. The assumption about their existence is based on our previous diagrams of deep-seated processes and thermal models consistent with the hypothesis of advection and polymorphism (APH). Certainly, the problem cannot be easily solved in regard to this endogenous regime. Zones of recent activation, which are characterized by a fundamentally different type of velocity profiles of the upper mantle, are widespread on the platforms. Based on previously constructed velocity profiles for all continental platforms, areas with an inactive regime are revealed. The South American platform is an exception. We have identified a platform-specific velocity profile within the territory of Ukraine only in a limited interval of depths. In other cases, the travel time curves clearly show that seismic waves travel through the mantle beneath the platforms themselves and zones of recent activation. A special study of the mantle beneath the territory of Ukraine shows that these zones occupy about half of the platform. The platforms in other regions and continents are characterized by a similar situation; the travel time curves are almost identical. We have adopted the velocity profile that is agreeable to the average experimental travel time curve and which is close to the profile averaged between the APH-based simulated profiles for the platform and the zone of recent activation. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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