V. Babuska et J. Plomerova, LITHOSPHERIC THICKNESS AND VELOCITY ANISOTROPY - SEISMOLOGICAL AND GEOTHERMAL ASPECTS, Tectonophysics, 225(1-2), 1993, pp. 79-89
We compare inferences of regional variations in the lithospheric thick
ness in central Europe based on three types of observations. Seismolog
ically determined thicknesses derived from representative P-wave resid
uals agree in most regions both with the magnetotelluric inferences of
depths of the top of a layer of increased electrical conductivity and
with the geothermally based calculations that allow inferences of the
lithospheric thickness from surface heat-flow data. The seismological
definition of the lithosphere as a high-velocity layer overlying the
low-velocity zone in the upper mantle seems to be close to the geother
mal concept in which the lithospheric base is defined by temperatures
near partial melting, decreasing the seismic velocities and increasing
the electrical conductivity. Interpretations of seismic data used for
constraining geothermal models of the deep lithosphere assume velocit
y variations to reflect mainly changes in the mineral composition. How
ever, recent observations of large-scale seismic anisotropy show clear
ly that, in the subcrustal lithosphere, velocity variations due to ani
sotropy caused by preferred orientations of olivine crystals can be mu
ch larger than the velocity variations caused by temperature or compos
itional changes.