What Rubber Faults Can Teach Us About Earthquakes
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Will Steinhardt
UC Santa Cruz
- Date & Time
- Location
- Hybrid - in person and online via MS Teams
- Host
- Sara Beth
- Summary
The behavior of faults, like many geophysical systems, is difficult to predict for three main reasons: 1) their dynamics span enormous spatiotemporal scales (microns to km, milliseconds to centuries) and thus are difficult to comprehensively measure, 2) faults have significant heterogeneity that can dominate observable behavior, and 3) they occur kilometers underground and thus are mostly observed indirectly. My research involves studying a fault made out of a transparent rubber that addresses each of these issues, allowing direct imaging of strains across the frictional interface, active control over normal stress heterogeneity, and that can undergo earthquake cycles in a few seconds. Most importantly, this system has slip events that do not fail the entire interface and instead stop because they run out of energy or run into a barrier. This means that the stress state on the fault is a function of both a complex geometry that evolves over slip, and the residual stress built over historical slip events, just like faults in the earth. As a result, this rubber fault also follows a broad range of statistical behaviors exhibited by faults including the Gutenberg-Richter relationship, Omori’s Law, and both magnitude and normal stress independent stress drops.
In this talk, I will discuss our observations of locking events that precede slip events on the fault and have predictive power over the size, timing, and location of future slip events. In addition, I will show how we have identified seismologically measurable parameters that can be used to evaluate the relative likelihood of earthquakes that grow through a single monotonic growth and decay phase and those that grow via the linking of multiple disparate asperities. Finally, I will show some preliminary data about how the distribution of strains on faults evolve over multiple slip cycles.