Geodynamical implications from the correlation of surface
geology and seismic tomographic structure
Ondrej Cadek and Hana Kyvalova
Department of Geophysics,
Charles University, Prague, Czech Republic
David A. Yuen
Department of Geology and Geophysics
and Minnesota Supercomputer Institute,
University of Minnesota, Minneapolis, USA
Abstract:
We have investigated the relationship between the lateral seismic structure
in the mantle and the geological features associated with major mantle
upwellings, the oceanic ridge-systems and the hotspots. Using the technique
of correlation analysis, we have identified that these features extend quite
deeply into the mantle to a depth of around 1300 km. This finding is surprising
for the ridges because this indicates that the style of upwelling is rather
active and is somewhat two-dimensional in character. The confidence level of
the correlation between ridges and slow seismic regions is maintained at a level
greater than 90\% to a depth of 1300 km. This is followed by a sharp decrease
to 50\% at 1700 km. A similar correlation pattern is found for the hotspots.
In both cases the correlation maxima lie close to a depth of 1000 km, where
remnants of old slabs have recently been revealed by correlation analysis.
These findings suggest that dynamical processes at a depth of around 1000 km
can be linked with surface tectonic activities. This correlation disappears
at a depth of around 1500 to 1700 km. Certain features of the surface tectonic
pattern can again be recognized around a depth of 2000 km and in the deepest
mantle where major hotspot plumes and the remnant old lithosphere are the
dominant features. There may be some dynamical relationship between the ridge
system and the two megaplumes. We have proposed a physical mechanism based on
viscous heating within megaplumes to explain the two peaks in the correlation
between the hotspots and the seismic heterogeneities.