Investigating Lithospheric Heterogeneity of the North American Craton with Multiple Seismological Methods

Purdue University, West Lafayette IN

Investigators

Abstract

The relatively stable cores of the Earth’s continental lithosphere, referred to as cratons, are considered “stable” tectonic features that are generally resilient to destruction and recycling. This resilience does not mean that cratons are not deformed by tectonic proceses. Globally, within the interior of cratons, there are a large number of local subsidence, uplifts, and breakups that form basins, mountains, and rifts. These tectonic features are also localities of important mineral and petroleum resources, as well as earthquakes. Despite the scientific and societal importance of cratons and their associated tectonic features, it is unclear how these features form and how cratons survive the long (billions of years) history of tectonic evolution. This project will examine the seismic signatures within the North American midcontinent by constructing multiple types of seismic models. These seismic models will provide constraints on the tectonic mechanisms that have modified the North American cratonic lithosphere. This project will support graduate and undergraduate students in seismic data analysis and interpretations. By working with the outreach office at Purdue University, this project will create an educational video series on the geology and tectonics of the Midwest U.S., which will be accessible to the public. Cratons are normally considered “stable” tectonic features generally resilient to destruction and recycling. This thought has become increasingly questionable with recent observations from geophysical imaging, geological surveys, and geodynamic modeling that support significant structural and compositional modifications of the cratonic lithosphere. This project will construct multi-type seismic models of the North American cratonic interior with multiple methods, including full-wave ambient noise tomography, plan-wave migration receiver functions, and seismic anisotropy analysis. With the new structural constraints, this project will systematically evaluate four previously proposed end-member scenarios for the evolution of the cratonic lithosphere. The result of this project will shed light on several fundamental questions in Earth sciences: 1) what are the processes that modify stable cratons? 2) why and how did cratons survive the long history of tectonic events? And 3) how do pre-existing structures influence later deformation? The outcome of this project also has important implications across geoscience disciplines studying continental evolution, such as seismology, geology, geomorphology, petrology, and geodynamic modeling. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.