Full Text View Subduction of the Chile Ridge: Upper mantle
structure and flow |Table of Contents| Search GoogleScholar for
Search GSA Today We deployed 39 broadband seismometers in
southern Chile from Dec. 2004 to Feb. 2007 to determine
lithosphere and upper mantle structure in the vicinity of the
subducting Chile Ridge. Body-wave travel-time tomography clearly
shows the existence of a long-hypothesized slab window, a gap
between the subducted Nazca and Antarctic lithospheres. P-wave
velocities in the slab gap are distinctly slow relative to
surrounding asthenospheric mantle. Thus, the gap between slabs
visible in the imaging appears to be filled by unusually warm
asthenosphere, consistent with subduction of the Chile Ridge.
Shear wave splitting in the Chile Ridge subduction region is
very strong (mean delay time ~3 s) and highly variable. North of
the slab windows, splitting fast directions are mostly trench
parallel, but, in the region of the slab gap, splitting fast
trends appear to fan from NW-SE trends i