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Science 20 August 1971:
Vol. 173. no. 3998, pp. 719 - 722
DOI: 10.1126/science.173.3998.719
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Articles

Tectonic Movement in the Chile Trench

C. R. B. Lister 1

1 Geophysics Program and Department of Oceanography, University of Washington, Seattle 98105

An acoustic reflection profile across the Chile Trench off Valparaiso shows the trench floor to have a substantial sediment accumulation that is far from flat-lying. The morphology is transitional between the flat-lying sediment fill to the south (labeled a type I trench) and the bare V-notch character farther north (labeled type II). A sharp seaward slope break, downbowed reflectors, and a landward downthrown normal fault suggest that the oceanic lithosphere is failing in shear. This mode of failutre is more consistent with the observed features of trenches and Benioff zones than is the concept of bending and underthrusting.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)