Correlation analysis between subduction in the last 180 Myr and lateral seismic
structure of the lower mantle: Geodynamical implications
Hana Kyvalova and Ondrej Cadek
Department of Geophysics,
Charles University, Prague, Czech Republic
David A. Yuen
Minnesota Supercomputer Institute,
University of Minnesota, Minneapolis MN 55415, USA
We have calculated the correlation between four recent
tomographic models and
reconstructions of past
subduction sites to
estimate the present positions of the lithosphere subducted during the
Cenozoic and the Mesozoic.
A significant correlation
at a depth of about 1000 km for subduction younger than 120 Myr,
remnants of subduction older than 120 Myr are detected close
to the core-mantle boundary (CMB).
Somewhere in the depth range of 1300-2600
a gap exists where no significant
correlation is found in any time.
The results suggest that the slabs do not pass through the lower mantle
It is possible that both regimes,
the catastrophic and the steady-state,
may be important for different time periods. Fast seismic anomalies
close to the CMB may be associated with a past catastrophic event,
while the good correlation
in the upper part of the lower mantle may be explained
by a steady-state model. Other explanations for
the very good correlation found at a depth of about 1000 km are either a
predicted perovskite phase transition
or a chemical boundary suggested by seismic array analysis.