Collaborative Research: Paleoseismology and Paleogeodesy of the Sumatran Subduction Zone

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EAR-0208508Kerry SiehThis study continues investigations of the paleoseismology and paleogeodesy of the Sumatran subduction zone in order to determine possible regularity of periods between fault ruptures, repeatability of pattern of slip on faults, influence of geologic structure on fault rupture, and variation of seismic/aseismic coupling with time. The centerpiece of the study is the use of coral heads (Porites and other genera) that are sensitive to sea level changes with uncertainties of a few centimeters. Annual growth bands give time-series with relative errors of a few years and U-Th dating of the heads gives dates with errors of a decade. The magnitude of vertical deformation associated with earthquakes (paleoseismology) and deformation in intervals between earthquakes (paleogeodesy) are being determined from these data. Results are being modeled and historical earthquakes (seismograms from a variety of sources) are being used to determine if segment boundaries influenced dimensions of historical ruptures. The specific goals of this project are to: (1) better characterize source parameters of 1681, 1797, and 1833 events; (2) determine southern limit of these events; (3) extend record back to 14th century; (4) determine source characteristics of 1861 and 1907 quakes; (5) model historical seismograms of large quakes on Sumatran fault; (6) characterize aseismic strain events in 1861, 1797, and 1833 regions.