Laboratory Insight Into Seismic Estimates of Energy Partitioning During Dynamic Rupture: An Observable Scaling Breakdown

Abstract

AbstractWe investigate energy partitioning using seismological methods of seismic ruptures with estimated submicron levels of slip in the laboratory. Estimates inferred from recorded seismic waves are founded on microscale phenomenological friction experiments in the laboratory and appear to be constrained by inherent assumptions. In this concerted study, we build on the methods used to absolutely calibrate an array of piezoelectric transducers in a direct shear laboratory apparatus. We found that flat‐broadband sensor behavior allowed us to study source extent parameters using spectral source models that are typically used to interpret small to moderate‐sized earthquakes. We computed the corner frequencies, low‐frequency plateaus, and high‐frequency spectral falloff exponent using single‐station assumptions. Moment magnitude ranged from −9<Mw<−7.5 and slip was on the order of nanometers to micrometers—extending our understanding of source parameters studied via seismic waves. A number of findings are highlighted: (i) Variations in spectral falloff with corner frequencies followed the observations made in natural conditions. (ii) Corner frequency shift phenomenon was observed (fcP/fcS∼ 1.34) and was attributed to source finiteness rather than wave propagation effects. (iii) Events were stress overshoot as determined by the Savage‐Wood efficiency. (iv) The empirical power law scaling relationship between fracture energy and slip, given as, wherenG=1.28 appears to break down with seismological estimates made at the mining scale (nG=1.86) and laboratory scale (nG=2.35). This break in scaling may be related to the types of off‐fault energy sinks that are inherently captured in the seismological interpretation of fracture energy.