Subduction of the Chile Ridge: Upper mantle structure and flow

[摘要] We deployed 39 broadband seismometers in southernChile from Dec. 2004 to Feb. 2007 to determine lithosphere and upper mantle structure in the vicinity of the subductingChile Ridge. Body-wave travel-time tomography clearly shows the existence of a long-hypothesizedslab window, a gap between the subducted Nazca and Antarctic lithospheres.P-wave velocities in the slab gap are distinctly slow relative to surrounding asthenosphericmantle. Thus, the gap between slabs visible in the imaging appears to be filledby unusually warm asthenosphere, consistent with subduction of the Chile Ridge. Shear wave splitting in the Chile Ridge subductionregion is very strong (mean delay time ~3 s) and highly variable. North ofthe slab windows, splitting fast directions are mostly trench parallel, but, inthe region of the slab gap, splitting fast trends appear to fan from NW-SE trendsin the north, through ENE-WSW trends toward the middle of the slab window, to NE-SWtrends south of the slab window. We interpret theseresults as indicating flow of asthenospheric upper mantle into the slab window.

[学科分类] 地质学

[关键词] Fire safety;fatal fires;smoke alarms