Revealing Quaternary evolution of North American tectonics with geologic block models

The University Corporation, Northridge, Northridge CA

Investigators

Abstract

This project will reconstruct tectonic motion in western North America over the last 2.6 Million years. This will be accomplished by combining geologic and satellite-based data with modern mathematical modeling techniques. The distribution of tectonic motion in the Earth’s crust is directly related to the potential size and location of future earthquakes and is therefore a critical component of the United States National Seismic Hazard Model, which is used by insurance companies, government officials, and land use managers, as well as in public outreach. This project will advance tectonic modeling and also help identify potential limitations of geologic and satellite-based data, ultimately improving seismic hazard for the benefit of society. The project will support the full participation of women and underrepresented minorities in STEM and improve college-level STEM education: results from this project will be incorporated into a new laboratory exercise for all Geology and Geophysics majors at California State University Northridge (a Minority Serving Institution) that will be made publicly available, and the PI is committed to recruiting student research assistants from underrepresented minorities. This project will evaluate discrepancies between geologic and geodetic fault slip rates in western North America to interrogate the fundamental nature of Quaternary tectonic deformation in space and time. Fault slip rate can be estimated at points along a fault using tectonic geology (geologic slip rates), or by using models based on satellite-based geodetic measurements such as Global Navigation Satellite Systems (GNSS) including the Global Positioning System (GPS) (geodetic slip rates). Discrepancies between geologic and geodetic slip rates may reflect true spatial or temporal variations, limiting interpretation in terms of contemporary tectonics and seismic hazard. To address slip rate discrepancies, the research team will create the first fully geologic block model of the Pacific-North America plate boundary. Typically, block models are constrained by GNSS data; however, the team will update the block modeling methodology to constrain the models exclusively with geologic slip rates. This work represents a significant advance in tectonic block modeling, including an innovative automated block closure algorithm that will fundamentally improve how block models are developed, tested, and interpreted. Geologic slip rate constraints will be subdivided based on the age range to reflect North America tectonics over geologic time. Directly comparing geologically-constrained block models with traditional GNSS-based block models will isolate the role of geologic vs. geodetic observations in inferring plate boundary-scale tectonic deformation. Funding for this project is provided by NSF EAR Tectonics Program. 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.