CAREER: Intraplate tectonics and deep crustal faulting in Rural Alaska

点击翻译按钮获取中文摘要

This project applies earthquake modeling and seismic wavefield simulations to a new seismic data acquisition in order to characterize a major, yet unknown, fault zone within one of the most active intraplate regions of North America. Located 700 km north of the Alaska-Aleutian trench, the Nenana basin is a 7 km deep, active sedimentary basin aligned with the 200 km long Minto Flats seismic zone. The seismic zone contains the highest concentration of deep (15 km) crustal seismicity in central Alaska. Two deep events include a 2012 triggered earthquake with a 24 s nucleation phase, and also a 1995 Mw 6.0 earthquake that ruptured a small portion of the fault zone and strongly shook the region. The three-dimensional fault zone structure and the relationship between the active sedimentary basin and the sub-basin faulting are unknown, in part because no seismic station has ever been deployed in this remote region. The Tanana river provides access for a strategic 12-station deployment targeting the fault zone. Seismic waveforms from local earthquakes will be used to develop a catalog of accurate earthquake locations. A new moment tensor catalog for local events will characterize the style of faulting. Seismic wavefield simulations of earthquakes within the fault zone will be used to explore the influences of fault complexity, earthquake ruptures, and basin structure on the regional seismic wavefield. Modeling of the seismic data will help determine whether the anomalously deep crustal seismicity is related to overlying basin formation, to underlying slab-driven processes, or to laterally driven processes.The seismic waveforms collected during this experiment will be the first ever recorded in this active tectonic region, and they will provide a valuable resource for future geophysical studies in central Alaska. Characterization of the Minto Flats fault zone will provide fundamental constraints on the competing tectonic models for basin formation and deformation within central Alaska. The project has a substantial education component that includes high school students from Nenana, as well as undergraduate and graduate students. Field-based teaching modules, classroom-based teaching modules, and annual field trips to science exhibits in Fairbanks will engage Nenana high school students in earthquake science and active tectonics of Alaska.