EAR-PF: Active Tectonics and Crustal Structure of Northern Alaska

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Dr. Bryant Chow has been awarded an NSF EAR Postdoctoral Fellowship to investigate the question of why earthquakes occur where they do. This work will take place at the University of Alaska Fairbanks under the mentorship of Dr. Carl Tape. The Earth’s crust is the outermost shell where all human activity takes place. Fractured into many tectonic plates, the crust hosts disastrous events, such as earthquakes, tsunamis, and volcanic eruptions, near its surface. Earthquakes typically occur where two or more plates meet, but they can also occur far from plate boundaries. The processes that cause these earthquakes are not well understood. This project seeks to characterize Earth’s crustal structure, linking deep-Earth processes with surface geological activity to explore why earthquakes occur where they do. The work will investigate plate tectonic processes and crustal structure in northern Alaska, an understudied region far from plate boundaries that has hosted M4 earthquakes. The goal is to characterize earthquakes and develop high-resolution models of the crust in order to understand how tectonic forces are transferred far into the interior of plates. Although population density in northern Alaska is low, earthquake hazard remains important for infrastructure, environmental, and industrial purposes and is critical for development in the region. Alaska’s North Slope is a major oil producing region for the United States, and northeastern Alaska is home to the largest national wildlife refuge in the country. This project involves outreach to local communities in northern Alaska using novel teaching tools to convey earthquake risks and hazards. Additionally, Dr. Chow will produce a comprehensive catalog of models that can be used for characterizing earthquake hazard. This project proposes a detailed seismotectonic investigation of northern Alaska to constrain mechanisms controlling tectonics in and around the region. Northern Alaska features diffuse seismicity and large-scale deformation far from the plate boundaries. However, the structures and processes involved are not well understood. Due to its remoteness, difficulties in mapping and monitoring of northern Alaska have resulted in historically sparse coverage. This changed following the deployment of the EarthScope Transportable Array in Alaska, with years of high-quality seismic data now available for a comprehensive study. This project involves investigation of two scientific questions: Are deformation and structure in northeastern Alaska consistent with (1) far field deformation from plate convergence 1000 km away? and (2) extrusional extension of western Alaska? This work will advance understanding of how global geodynamic processes shape continental scale tectonics and relate to regional deformation and local seismicity, using waveform cross-correlation techniques and 3D numerical waveform simulations. Detection and re-location of seismicity will be followed by inversion of seismic moment tensors to constrain fault structure and deformation characteristics. Waveform simulations will be used to validate existing tomography models of northern Alaska and for subsequent full-waveform tomography, which will result in high-resolution structural models of the crust and upper mantle. Ambient noise adjoint tomography will provide a velocity model of northern Alaska with resolution on the order of tens of km. A subsequent earthquake adjoint tomography inversion will refine a northeastern subset of this model, resulting in km scale resolutions. The success of these tasks will lead to refined earthquake catalogs, high resolution velocity models, and detailed interpretations of tectonic processes for northern Alaska.This project is jointly funded by the EAR Postdoctoral Fellowship program, the Established Program to Stimulate Competitive Research (EPSCoR), and the EAR Geophysics 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.