Collaborative Research: Paleoseismology and Paleogeodesy of the Sumatran Subduction Zone

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9903301 SiehPrevious work has demonstrated that coral "microatolls" offer an unrivalled opportunity to test models of earthquake recurrence, because they record vertical deformation through several large-earthquake cycles quite precisely in their morphology and annual banding. Between the western coast of Sumatra and the trench of the Sumatran subduction zone, several collected slabs of head corals record sea-level changes caused vertical interseismic and coseismic deformation. On the islands of the outer-arc ridge, work has documented sudden emergence of 1-2 meters during the giant earthquake of 1833, and corals uplifted similar amounts during two earlier events about AD 1608 and 1380 suggest such events might recur about every 230 years. In periods between these large emergence events, coral heads record rapid submergence within 130 km of the trench, rapid emergence between 130 and 200 km of the trench, and near-stability on the mainland coast, about 240 km from the trench, and this pattern may be consistent with interseismic strain accumulation models. This proposal will continue the investigation of the Sumatran subduction zone, studying the giant 1833 event and its predecessors using coral stratigraphy, morphology, and geochronology.