Determinism and stochasticity in laboratory earthquakes final size driven by interface heterogeneity

Doron Morad, Shahar Gvirtzman, Jay Fineberg, & Emily E. Brodsky

Published September 8, 2024, SCEC Contribution #14037, 2024 SCEC Annual Meeting Poster #163

The study of seismic waves is the most commonly used tool to determine the rupture dynamics of an earthquake. Earthquake source parameter estimates use difficult-to-assess assumptions about the source time function and path which are necessary in the absence of any more direct information about the mechanics of earthquake rupture. We address the need here with a quantitative analysis of laboratory-scale seismic measurements coupled with direct and real-time dynamic rupture measurements derived from high-speed imaging during rupture of laboratory faults. In this study, we placed a set of acoustic sensors on the upper boundary of a transparent (PMMA) block. We calibrated it, and designed the experiment so the acoustic sensor is located sufficiently far from the frictional source (i.e., seismic source) to be treated as a remote seismic station. Then we investigate the nature of ruptures early growth history by correlating the measured seismograms to the rupture final size. We found that for homogeneous interfaces the moment rate as inferred directly from the imaged ruptures accurately predicts the amplitude of the farfield seismogram. We additionally observed an early increase in the rate of rupture growth that correlates with increasing event magnitude. Thus, under simple conditions the event final size can be predetermined. We then investigate the early growth history of ruptures in a more heterogeneous interfaces by introducing local barriers on the interface and found a significant drop in magnitude determinism during the early stage of the rupture. We suggest that higher available elastic energy promotes both faster and larger ruptures when the stresses is more evenly distributed. Thus, the fracture of a large, loaded asperity might be expected to have a different moment rate release and a longer ultimate rupture.

Key Words
Fault rupture, Acoustic sensor, Source time function

Citation
Morad, D., Gvirtzman, S., Fineberg, J., & Brodsky, E. E. (2024, 09). Determinism and stochasticity in laboratory earthquakes final size driven by interface heterogeneity. Poster Presentation at 2024 SCEC Annual Meeting.

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