Collaborative Research: A Paleoseismic Record of Repeated Great Earthquakes on the Sunda Subduction Megathrust, Northern Sumatra

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The 2004 Andaman-Aceh earthquake and tsunami focused global attention on the northernmost part of the Sumatran subduction zone and raised questions about the past geologic history of the Sunda megasthrust offshore of northernmost Sumatra. The objective of this research project is to understand the long-term seismic behavior of the Sunda megathrust of northernmost Sumatra through a study that integrates forefront techniques of paleoseismology, geodesy, geochronology and paleo-environmental reconstruction using microfossils. The study will establish a subduction zone chronology for the northernmost past of the Sumatran subduction zone offshore of northern Sumatra going back approximately five thousand years. The reconstructed subduction zone history will include investigation of several critical components that help define the nature of subduction zone tectonics at convergent margins. These components include recurrence interval between subduction zone earthquakes, amounts of coseismic and interseismic vertical land level changes, documentation of subsidence precursory to the main coseismic subsidence event, documentation of uplift after the main coseismic subsidence event caused by slow, down dip afterslip on the megathrust and finally, development of a chronology of tsunami that invades the Sumatran coast.Results of this research will help define the history of subduction zone earthquakes and tsunami along the west coast of northern Sumatra going back several thousand years. A long-term record of subduction zone earthquakes that spans at least three or four earthquake cycles will provide realistic estimates of the average time between earthquakes and tsunamis similar to the earthquake and ensuing tsunami that struck the west coast of northern Sumatra in December 2004. Results from this project will be disseminated among the inhabitants of the region and with Sumatran governmental agencies. These results will establish that earthquake and tsunami are recurrent events that should be anticipated and that require disaster planning.