Studying Earthquakes in the Lab
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, Gregory McLaskey, Civil and Environmental Engineering, is conducting fault-rupture experiments in a controlled laboratory environment on meter-scale rock samples. McLaskey is using 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 let researchers simulate natural earthquakes in the laboratory.
More than 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. McLaskey is, first, conducting fluid injection experiments on small transparent plastic samples, where fluids can be tracked visually, then on meter-scale rock samples, where fluids will be monitored acoustically. The results will be compared to those of 20-m-scale fluid-injection experiments at Grimsel underground laboratory in the central Swiss Alps. The research is improving the interpretation of natural earthquake and tremor seismograms, and in turn, earthquake hazard assessment.