Boslough et al. [14], however, used shock-hydrodynamic
simulations to generate source functions for
seismological modeling of the entire Earth, and
estimated the effects of antipodally focused seismic
waves from a Chicxulub scale impact (10-km-diameter
asteroid impacting at 20 km/s). They found that the
largest displacements (F 10 m at antipode), stresses,
and strains occur in the antipodal lithosphere and
upper asthenosphere, and that these large amplitudes
are due primarily to the convergence of fundamental
mode Rayleigh surface waves. Although peak stresses
and strains fall off rapidly with depth beneath the
antipode, the seismic energy remains sharply focused
down to the core–mantle boundary. Indeed, motions at
the core–mantle boundary are greater beneath the
antipode than beneath the impact site itself.
Because the focused seismic energy would be most
strongly attenuated in the partially molten asthenosphere,
Boslough et al. [14] suggested that dissipation
of the seismic energy could cause heating and
additional melting, and possibly antipodal flood basalt
volcanism. Ivanov and Melosh [48], however, concluded
that the antipodal thermal anomaly generated
by a Chicxulub scale impact would be negligible.
Accepting that the upper mantle is likely hotter and
more fertile than generally presumed in dstandardT
mantle plume models [8,9], lithospheric fracturing by
focused seismic energy from large-body impacts
might have played a major role in the formation of
antipodal flood basalts. As shown in Boslough et al.
[14], peak antipodal displacements, stresses, and
strains would occur throughout the lithosphere.
