ABSTRACT

How plate tectonics have shaped the Earth's surface geology (such as mountain building, basin formation, landscape evolution, volcanic activities and earthquakes) remains a fundamental question in geosciences. Key to this question is the uncertain variation in the style and dynamics of subduction, a process when cold oceanic plates recycle into the Earth's warm interior. In this proposal, the PI plans to study the causes and consequences of flat-slab subduction (i.e., down-going plates travel sub-horizontally beneath the lithosphere before sinking into the mantle) that has found to be greatly affecting the evolution of continents. This problem has been traditionally difficult to understand due to the many complexities and unknowns involved. Fortunately, the recent progress in geophysical data acquisition and high performance computing make it possible to tackle this important geodynamic problem by building sophisticated physical models using various techniques of data assimilation. Using the PI's previous experience on constructing both forward and inverse data-oriented models (similar to how weather prediction works), the investigator will explore the subduction history in South America, North America and East Asia, where multiple flat-slab epochs have occurred, resulting in the unique geology surrounding the Pacific Ocean. Results from this project will help to better understand not only basic earth evolution but also formation of natural hazards and resources. This project also aims at enhancing communication and education of geodynamic research to both researchers and students. By designing an online interactive geodynamics forum, the PI hopes to promote geodynamic research to the broad Earth science community, and to help interested users to learn geodynamic modeling. The PI plans to develop this geodynamics group into a community hub for doing cross-disciplinary and collaborative research. With multiple research-based flipped-classroom activities, the PI also
aims to build a modern education culture, with a key focus on nurturing high quality geoscientists for the new century. Finally, this proposal will support and train two PhD students and several undergraduates.

It is widely accepted that subduction processes, especially flat-slab subduction, strongly influence the geological evolution of continents and mantle dynamics. However, both the causes and consequences of flat-slab subduction remain elusive. This is largely due to the difficulty to realistically simulate the complex behavior of subduction and its interaction with the overriding continents. In this proposal, the PI plan's to improve our understanding on the physical mechanisms and tectonic consequences of flat-slab subduction by combining advanced data-oriented physical models with geological and geophysical constraints. In practice, he will combine well-established subduction modeling tools (both forward and adjoint methods) with data constraints from multiple disciplines. This comprehensive modeling effort will be applied to three different geographic locations (South America, North America, and East Asia) where flat subduction occurred in the past or is still going on now, and where several different physical mechanisms for slab flattening (subduction of various buoyancy features, fast plate motions, and hydrodynamic suction from the thick overriding plate) could be evaluated. The multidisciplinary nature of this work will make the results highly relevant to many other research fields.

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