CAREER: Large-scale laboratory-generated earthquakes to study earthquake scaling and fluid-fault interactions.

点击翻译按钮获取中文摘要

Earthquakes occur at a variety of scales. Large earthquakes threaten our cities while tiny ones can be used to understand and monitor underground processes. Subsurface fluids play an important role in earthquake source processes. They can trigger fast, destructive, earthquakes or promote slow, nearly-silent, fault slip which can generate weak tremors. To better understand the role of fluids in earthquake processes, the PI will carry out fault-rupture experiments in a controlled laboratory environment on meter-scale rock samples. These experiments will be a stepping stone between previous smaller-scale laboratory studies and larger field studies. In the experiments, sensors will track the fluids on the fault planes and monitor acoustic wave propagation by methods analogous to those used in seismology. The goal is to better understand the role of fluids in the generation of tremors and other seismic signals, and to scale these observations to natural events. This work will improve our capability to interpret seismic observations, notably tremors, hence earthquake hazard assessment. It will also support a graduate student and educational outreaches toward undergraduates and the public.This project focuses on the fundamental processes underlying fluid-assisted earthquake triggering and frictional slip, and the scaling of laboratory observations to the field. The team will carry out rock-rupture experiments. They will use a new apparatus that squeezes a 3-m slab of granite and can generate magnitude-2.5 dynamic slip events, where rupture nucleation, propagation and termination occur within the sample. These new large-scale experiments with confined ruptures allow simulating natural earthquakes in the laboratory. Over 60 sensors are installed on the sample, the laboratory equivalent of seismic and geodetic networks. The simultaneous measurements link seismic observations to fault slips and stress changes. Fluid injection experiments will be first carried out on small transparent plastic samples, where fluids can be tracked visually, then on meter-scale rock samples where fluids will be monitored acoustically. Finally, the results will be compared to those of 20-m-scale fluid-injection experiments at Grimsel underground laboratory in the central Swiss Alps. The goal is to improve the interpretation of natural earthquake and tremor seismograms, hence earthquake hazard assessment. This 5-year project will also support a graduate student and the development of a wooden footbridge building competition. It will engage young people in 4-H programs and at community colleges in up-state NY rural counties, traditionally underrepresented in STEM. The goal will be to scale up a 14 ft. wooden bridge competition that started as a Cornell class project to footbridges that meet local needs in the City of Ithaca and other communities.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.