Deep structure of the Vanuatu (New Hebrides) island arc: Intermediate depth collision of subducted lithospheric plates

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Abstract
The distribution of earthquake foci in the Vanuatu region is interpreted as a result of the intermediate depth collision of 2 differently inclined lithospheric slabs produced by 2 consecutive subduction cycles of the same polarity. A correlation between the depth of penetration of the presently active subduction zone and the major physiographic units of the ocean floor implies a nonuniform rate of subduction along the New Hebrides trench due to the hampering effect of the main structural features of the subducting Australian plate. Two subduction cycles accompanied by fracturing in the basement of the archipelago can explain the formation of 3 belts of islands of the Vanuatu Archipelago. The well-investigated geology of the region allowed us to correlate the successive stages of the subduction process with the geological evolution of the Vanuatu island arc.