Relative Structural Complexity of Plate‐Boundary Fault Systems Controls Incremental Slip‐Rate Behavior of Major Strike‐Slip Faults

Abstract

AbstractA comparison of published incremental fault slip rates from four major strike‐slip faults with the proximity and number of other active faults in the surrounding plate boundary systems shows that the behavior of the primary fault is correlated with the structural complexity of its tectonic setting. To do this, we characterize the relative structural complexity of the fault network surrounding a fault location of interest by defining the coefficient of complexity, which 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 primary faults of the Alpine, San Andreas, North Anatolian, and Dead Sea fault systems reflects the proximity, number, and activity of their close neighbors. Specifically, 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. Our results provide a potential means for better evaluating the future behavior of large plate‐boundary faults in the absence of well‐documented incremental slip‐rate behavior, and may help improve the use of geological slip‐rate data in probabilistic seismic hazard assessments.