Direct Measurements of Slow Slip Events on Novel Laboratory Fault Show Constant Stress Drop

Will Steinhardt, & Emily E. Brodsky

Published August 16, 2021, SCEC Contribution #11531, 2021 SCEC Annual Meeting Poster #159

Slow slip events are a critical part of the seismic cycle. An important debate about slow slip revolves around whether they have magnitude-independent stress drops as is observed for regular earthquakes. Generally, stress drops for slow slip events appear to be lower than ordinary earthquakes, but their scaling with moment (or equivalently the scaling of duration with moment) is debated. We have developed a new type of experimental system to better understand slow slip events, and specifically, how stress scales over a range of magnitudes, on a scaled down, transparent, three-dimensional laboratory fault. In addition to direct control over the shear and normal force, this system allows the unique ability to actively control the heterogeneity of the fault through both the fault roughness and the normal stress distribution, while offering direct imaging of interfacial strains at high spatiotemporal resolution. We have generated events in this system of magnitude -10 to -8, and seismic moments of 10^-6 to 10^-3 N-m, for both homogeneous stress distributions as well as single large asperities. While we observe markedly different dynamics in each case, both stress distributions show a cubic scaling of moment with rupture length, which is consistent with a constant stress drop. This implies that slow slip events in the lab reproduce magnitude-independent stress drops, regardless of heterogeneity. In addition, it shows that our scaled laboratory system captures the relevant dynamics to study slow slip while offering unique experimental control and measurement.

Key Words
fault mechanics, experiment, slow slip, stress drop

Citation
Steinhardt, W., & Brodsky, E. E. (2021, 08). Direct Measurements of Slow Slip Events on Novel Laboratory Fault Show Constant Stress Drop. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)