Collaborative Research: Great Earthquakes, Megathrust Phenomenology and Continental Dynamics in the Southern Andes

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The overall goal of the project is to understand the processes that created and now drive evolution of the modern Andes. In order to do that, we must understand the spatial and temporal variability of stresses generated in the upper plate by coupling at the plate interface and by viscous drag of the asthenosphere. Specifically, the project will focus on the 2010 Mw 8.8 Maule earthquake in Chile, the earthquake cycle along the Nazca-South America plate interface, orogenesis of the Andean system, and its relationship to crustal deformation and mantle flow. The project is structured around two main themes:? How does megathrust phenomenology influence or control the architecture, from forearc to backarc, of the Andean orogeny? ? How do geological materials, shallow structure and slab/mantle dynamics influence or control the behavior and evolution of the megathrust? The PI group will use GPS and INSAR to examine post-seismic transients and combine these with co-seismic data. They will combine many sources of GPS data (German - GFZ and US groups) that have been collected from 1993 to present over the entire orogen in an effort to develop a synoptic model. This includes data from 33 cGPS stations installed in Chile with NSF-RAPID funds immediately following the Maule earthquake. The regional extent of new analysis will include the rupture zone from the 1960 Mw 9.5 earthquake, which still shows post-seismic transient deformation. Among the important geodynamic processes that the project will address are (1) time-variable deformation in the aftermath of a great subduction-zone earthquake; (2) improved models of plate interface rheology and their implications for plate boundary earthquake cycles; and (3) interaction between plate boundary and intraplate deformation over time-scales from decadal to geological. In addition to GPS and InSAR observation of surface deformation, the project brings to bear a number of state-of-the-art observational and modeling approaches; earthquake location and source mechanism determination; geological and geochemical constraints on uplift and erosion rates; inversion for geometric and rheological parameters associated with the plate interface; and large-scale geodynamic modeling. The investigator team is highly qualified to take on these activities, and has a strong track record in previous work in the area. They have developed a strong set of collaborations, both in-country and with other international researchers working in the area.