Аннотация
Short-period seismic recordings at regional and upper mantle distances
from underground explosions at Novaya Zemlya demonstrate that propagation
across the continental shelf under the Barents and Kara Seas appears
to modify the partitioning of energy between Lg and Sn phases relative
to purely continental paths in the Eurasian crust. While the underwater
segments of the paths are relatively short, variations in bathymetric
characteristics from path to path influence the regional wave field,
with systematic behavior that can be used to establish empirical
amplitude corrections for regional phases. We analyze a large set
of Eurasian recordings to explore the relationship between regional
phase energy partitioning and bathymetric characteristics. Maximum
water depth along the path is the most influential factor for the
Novaya Zemlya data. It has strong linear correlations with the logarithmic
rms amplitude of Lg and the ratios Sn/Lg and P/Lg. The maximum water
depth probably reflects the extent of necking of the crustal wave
guide under the continental margin, which may disrupt Lg modes resulting
in Lg to Sn scattering, but there is surprising sensitivity to small
variations in bathymetry. Empirical relations like those found here
may be useful for nuclear yield estimation and discrimination for
regions such as the Korean Peninsula and Persian Gulf, where many
seismic phases traverse water-covered continental shelf with poorly
known crustal structure.
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