Integrating Laboratory-Generated Fault Slip Events with Acoustic Wave Measurements

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Despite continual advances and breakthroughs, large earthquakes remain a constant threat to society, largely due to difficulties in prediction. Observational geophysics can provide general information on the where and broadly when earthquakes occur, but more precise estimations require a fuller understanding of fault movement as a geophysical process, which can be gleaned from laboratory experiments. Recent breakthroughs have revealed that realistic, plate-rate driving velocities of cm/yr can reveal a tendency for fault slip instability that may result in not only earthquakes, but also a wide range of “slow slip” in natural samples, phenomena that cannot be captured at faster, more typical experimental driving rates. Here, I propose to leverage the tendency for frictional instability and various types of slip events to occur at plate-rate driving velocities. For samples determined to be frictionally unstable, we can induce slip events in these samples and also manipulate these slip events via lab-controlled parameters (normal stress and apparatus stiffness). We can measure the characteristics of these slip events, and measure any ensuing acoustic emissions (AEs) with a planned broadband acoustic measurement system installed on laboratory direct-shear devices. This facilitates a direct comparison between AEs in the laboratory and seismic measurements in the field. The AE data may be combined with machine learning routines and microstructural analyses to help maximize the identification of patterns in the data. The proposed project will address important questions in earthquake science such as the nature of slow earthquakes and the conditions conducive to fast, earthquake slip, and the possible identification of patterns in the mechanical and AE data that may be used as earthquake precursors to improve earthquake early warning.