Postdoctoral Fellowship: EAR-PF: Synthesizing Multiscale Earth Models to Enhance Exploration, Discovery, and Application

Dr. Rasheed Ajala has been awarded an EAR Postdoctoral Fellowship to conduct research and professional development activities under the mentorship of Dr. Folarin Kolawole at Columbia University and Dr. Daniel Trugman at the University of Nevada Reno. Our planet evolves using dynamic forces. These forces operate at different scales in both time and space. They drive tectonic processes. For example, they cause continents to rift, creating large ocean basins. Scientists use solid earth models to study these processes. The models describe the material properties of the earth. The models also exist at different spatial scales. The large-scale models are better for understanding large-scale tectonic forces. The small-scale models are also the most useful for studying small-scale forces. Yet, large-scale forces influence small-scale forces. So, comprehensive studies of tectonic processes should use multiscale earth models. Multiscale earth models have varying spatial scales. This project will conduct a multiscale investigation of continental rifting. The study location is the East African Rift System. It's one of the planet's largest and most active continental rift systems. It's also a young rift system with segments spanning continental rifting endmembers. The research findings will help with assessing hazards from volcanism and earthquakes. The project will establish a web service for developing multiscale earth models. The service will help scientists with limited computer skills in their work. Finally, the project will engage nontraditional undergraduate students with limited research opportunities. The project will address questions on the role of volatiles and preexisting weaknesses in controlling rift evolution by studying the structural variations in the crust and mantle of the nonvolcanic southern Tanganyika-Rukwa and northern Malawi rifts located north and south of the isolated Holocene Rungwe Volcanic Province, respectively, in the East African Rift System. The project will utilize seismic tomography techniques and local earthquake data to develop high-resolution crustal-scale 3D earth models that describe compressional and shear wave speeds. These models will be synthesized with existing regional mantle-scale models using the merging hybridization approach to produce composite earth models with varying spatial resolution that elucidate structures and processes at the crustal and mantle scale. The multiscale models will then be used with machine learning techniques to develop a high-resolution, low-uncertainty, and low-magnitude threshold earthquake catalog. The spatiotemporal seismicity pattern will aid in highlighting volatile migration pathways in the upper mantle and crust and deeply rooted extensional fault systems representing brittle deformation. Finally, the project will analyze shear waveforms from earthquakes in the catalog to produce crustal azimuthal anisotropy measurements to be interpreted with existing mantle shear wave splitting data. These anisotropy results will capture the subsurface deformation fabric and offer insight into the degree of deformation coupling between the crust and mantle. These analyses will help illuminate the interactive tectonic processes between the crust and mantle. The project findings will aid in developing a paradigm for nonvolcanic continental rifting without apparent magmatic influence. 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.