Speaker: Dr. Emma Hill; Earth Observatory of Singapore / Asian School of the Environment, Nanyang Technological University
Since 2004, the Sumatra subduction zone has been one of the most active on the planet, generating 30 moderate to great earthquakes (including four Mw>8) that produced complex patterns of postseismic deformation. All these events were recorded by the Sumatran GPS Array (SuGAr). The attached figure provides an overview of our results from this network. In this talk, we will present some of these results in the context of understanding behaviors that appear to be relatively persistent over time, and those that show greater variability. We will also discuss how these results fit into long-term behavior along the subduction zone as inferred from paleogeodetic observations. For example, coral data show that great earthquakes along one section of the megathrust are persistently bounded along-strike by structural features within the downgoing plate, including subducted fracture zones. Our data show varied types of slip near these boundaries and near areas that slipped little during great earthquakes. These varied behaviors likely result from structural and/or geometrical complexities of the megathrust. In contrast with the idea of persistent behavior of great earthquakes, the Mentawai patch (which is forecast from paleogeodetic data to produce a giant earthquake in the near future) has so far been breaking only in small sections. Coupling patterns along the megathrust are both spatially and temporally variable, and viscoelastic deformation following great earthquakes may persist for the majority of the (relatively short) earthquake cycle.