Relative structural complexity of plate boundary fault systems controls incremental slip-rate behavior of major strike-slip faults

Judith Gauriau, & James F. Dolan

Published July 20, 2021, SCEC Contribution #11058, 2021 SCEC Annual Meeting Poster #249

A comparison of published incremental fault slip rates from four major plate-boundary strike-slip faults with the proximity and number of other neighboring active faults shows that the behavior of the master fault is strongly correlated with the structural complexity of its tectonic setting. We characterize the relative structural complexity of the fault network surrounding a fault location of interest by defining the Coefficient of Complexity (CoCo), which is a metric that quantifies the density and displacement rates of the faults in the plate-boundary network at specified radii around the site of interest. We show that the relative constancy of incremental slip rates measured along master strike-slip faults of the Alpine, San Andreas, North Anatolian, and Dead Sea fault systems reflects the number, proximity, and activity of their close neighbors. Faults that extend through more structurally complex plate boundary fault systems exhibit more irregular slip behavior than faults that pass through simpler settings. We suggest that these behaviors are likely a response to more complex stress interactions within more structurally complicated regional fault systems, as well as possible temporal changes in fault strength and/or kinematic interactions amongst mechanically complementary faults within a system that collectively accommodates overall relative plate motion. The relationship between the steadiness or irregularity of incremental fault slip-rate and the relative structural complexity of the surrounding fault network revealed by our analysis suggests that the use of the CoCo metric could contribute to next-generation probabilistic seismic hazard analyses (PSHA) as a potential additional input that better accounts for slip rate variability. In the absence of well-documented incremental slip-rate behavior, our results may provide a means for evaluating future behaviors of large plate-boundary faults, and may refine the use of geological slip-rate data in PSHA.

Key Words
strike-slip plate boundary, fault network, fault slip rate, structural complexity

Citation
Gauriau, J., & Dolan, J. F. (2021, 07). Relative structural complexity of plate boundary fault systems controls incremental slip-rate behavior of major strike-slip faults. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)