CIG will have scheduled maintenance work beginning at 8 a.m. PDT on June 8, 2023. All running tool sessions will expire during the maintenance window. Please plan accordingly and we do apologize for any inconvenience.
Geophysical evidence suggests that some faults are frictionally strong, in agreement with laboratory measurements of quasi-static frictional strength (μ ≈ 0.6-0.8) for many crustal materials; whereas others studies have found that some faults are weak when compared to laboratory friction values (μ < 0.5). It has also been well documented that fault materials undergo a significant dynamic reduction in frictional strength when the sliding velocity accelerates to earthquake slip rates (on the order of meters per second). In this talk I will review our current understanding of fault strength evolution during the seismic cycle, then I will present results from two recent laboratory studies where we attempt to elucidate some of the dominant controls on fault strength both before and after an earthquake has occurred. Firstly, I will present results from a study where we investigate how geological heterogeneity in fault zones affects fault strength and stability; we find that heterogeneous faults are considerably weaker and more frictionally unstable than compositionally identical faults with an initially homogeneous structure. Then I will present results from some high-velocity friction experiments where we investigate how faults recover their strength after experiencing dynamic weakening during a seismic slip event. Our findings show that fault strength recovery (healing) occurs rapidly after high-velocity slip, which has important implications for our understanding of rupture dynamics and earthquake recurrence.