Abstract
Seismological evidence based on the spatial distribution and focal mechanisms of deep earthquakes in the North Fiji Basin supports a model in which Indo-Australian oceanic lithosphere, subducted at a former (11–8 Ma) position of the New Hebrides Trench, was detached as the trench migrated clockwise to its present position. A careful selection of well-determined hypocenters in the region, for the years 1964–1984, defines two segments of a deep Wadati-Benioff zone within the upper mantle at a depth of 545–655 km. The dips vary gently, the deep segments constituting an effectively flat zone of seismicity. The thin, slablike distribution of these hypocenters is similar to that in regions of active subduction. The horizontal extent of the relict slab segments is defined. It is apparent that lithosphere at this depth possesses enough strength to support earthquake generating stresses and to cause severe deformation of Pacific lithosphere subducted at the Tonga Trench. The slab segments have settled above the 700-km level and may represent a physical boundary which would preclude whole-mantle convection, at least in this area.
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Cooper, P., Kroenke, L.W. (1994). Deep Seismicity in the North Fiji Basin. In: Kroenke, L.W., Eade, J.V. (eds) Basin Formation, Ridge Crest Processes, and Metallogenesis in the North Fiji Basin. Circum-Pacific Council for Energy and Mineral Resources Earth Science Series, vol 15. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-85043-1_4
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DOI: https://doi.org/10.1007/978-3-642-85043-1_4
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