Invariance of Stress Drop Scaling for Slow Slip Events on Novel Laboratory Fault

Will Steinhardt, Emily E. Brodsky, Sam Dillavou, Shmuel M. Rubinstein, & Mary Agajanian

Published September 11, 2022, SCEC Contribution #12192, 2022 SCEC Annual Meeting Poster #137

Stress drop is a key seismological parameter for evaluating earthquakes, quantifying the change in stress on a fault due to a slip event. However, there is a fundamental discrepancy between the observed stress drop behavior of crustal earthquakes, where stress drop is largely independent of depth and thus normal stress, and both laboratory experiments and simple frictional models where stress drop scales proportionally with normal stress. This discrepancy holds for both ordinary earthquakes and slow slip events. We have developed a new transparent experimental fault made from elastomers that allows for direct observation of thousands of slow slip events at a frictional interface, whose ruptures are fully contained within the fault, and which offers active control over normal stress heterogeneity. Surprisingly, the slow slip events on our fault are largely independent of a wide range of fault parameters, including normal stress, normal stress heterogeneity, and to an extent, even frictional properties. These laboratory experiments have captured the key, previously inaccessible, feature of stress drop consistency seen in natural slip events. However, we observe a dramatic increase in stress drop and an emergent normal stress dependence as the fault area is reduced and increasing numbers of events reach the edge. This indicates that finite fault effects are a critical consideration when interpreting seismological stress drop.

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

Citation
Steinhardt, W., Brodsky, E. E., Dillavou, S., Rubinstein, S. M., & Agajanian, M. (2022, 09). Invariance of Stress Drop Scaling for Slow Slip Events on Novel Laboratory Fault. Poster Presentation at 2022 SCEC Annual Meeting.

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