One of the intriguing features of plate tectonics is that many active and ancient subduction zones have a pronounced arc-shaped morphology, with their topographic expressions stretching over hundreds to thousands of kilometers in length. Studying subduction, in general, is essential to understanding the evolution of the planet. More fully understanding the structure and dynamics of lithosphere, the relatively rigid outer shell of the Earth, subducting along highly arcuate plate boundaries will aid in constraining geologically recorded tectonic events, global plate motions, plate boundary deformation, and the role of subducted oceanic lithosphere in mantle convection. The overarching research goal of this CAREER award is development of an improved understanding of the structural and morphological evolution of arcuate shaped convergent margins through the study of four active arcs: the Mariana, Antilles, Betic-Rif, and Banda arcs, using a range of tools, including seismological imaging and geodynamic modeling. The expected findings will provide an important contribution to basic research on plate tectonics, an improved understanding of the structure and evolution of the tectonic plate boundaries, and the nature of seismicity in these regions. The educational goal is to train and prepare undergraduate graduate students as the next generation of geoscientists who are able to understand and effectively utilize both geophysical and geological data from subduction zones.
This CAREER award will investigate, in detail, the origin and evolution of the deep Earth structure of four target arcs. Improved imaging and modeling of these arcs will provide a way to test geodynamic hypotheses, for example, that curved subduction zones have evolved into their current configuration due to interactions of cold, dense oceanic lithosphere with positively buoyant features, such as oceanic plateaus or continental lithosphere, resulting in curved morphology as a result of trench rollback and slab fragmentation. Each of the four arc systems, have different length scales and topographic expressions, unique individual tectonic histories and plate configurations, yet they all exhibit highly arcuate convergent boundary structures and are bounded by buoyant crustal and lithospheric bodies at their cusps. This project proposes to examine these similarities and differences in order to better understand the geodynamic evolution and mantle structure at tightly curved convergent boundaries in terms of rollback, mantle flow, and the influence of buoyant "pinning" features at the ends of the arcs. This award will also fund development of an integrated education and research program based on understanding of seismicity, volcanism, mantle convection, plate tectonics, and geologic processes from both field and classroom based learning. The field component of the new Tectonophysics course will include deployment and collection of broadband seismic data along the several of the Antilles Islands and in northern Morocco, plus regional geologic mapping and sampling along portions of the active arcs. Both undergraduates and graduate students will participate in the course and other teaching modules developed through this award and will be part of USC's Problems Without Passports program that combine inquiry-based learning exercises with research in a foreign country.
