Seismotectonics and tectonic history of the andaman sea |
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| Authors: | Takao Eguchi Seiya Uyeda Tadashi Maki |
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| Institution: | Earthquake Research Institute, University of Tokyo, TokyoJapan |
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| Abstract: | The Andaman Sea is considered as an actively spreading back-arc basin. Seismicity and newly determined focal-mechanism solutions in the Andaman Sea area support this view. The tectonic history of the region is inferred from magnetic lineations in the northeastern Indian Ocean and the northward motion of Greater India. The mid-oceanic ridge which migrated northward along the east side of the Ninetyeast Ridge collided with the western end of the “old Sunda Trench” in the Middle or Late Miocene (10–20 m.y. B.P.). This ridge—trench collision released much of the compressional stress in the back-arc area and the continued northward movement of India that collided with Eurasia exerted a drag on the back-arc region, causing the opening of the Andaman Sea. In appearance, the subducted ridge jumped to the back-arc area. Thus, the Andaman Sea is not an ordinary subduction-related back-arc basin, but probably a basin formed by oblique extensional rifting associated with both ridge subduction and deformation of the back-arc area caused by a nearby continental collision. |
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