The Influence of Fault Geometrical Complexity on Surface Rupture Length

Abstract Propagating earthquakes must overcome geometrical complexity on fault networks to grow into large, surface rupturing events. We map step‐overs, bends, gaps, splays, and strands of length scales ∼100–500 m from the surface ruptures of 31 strike‐slip earthquakes, recording whether ruptures propagated past the feature. We find that step‐overs and bends can arrest rupture and develop a statistical model for passing probability as a function of geometry for each group. Step‐overs wider than 1.2 km, single bends larger than 32°, and double bends larger than 38° are breached by rupture half of the time. ∼20% of the ruptures terminate on straight segments. We examine how the distribution of geometrical complexity influences surface rupture length, inferring an exponential relationship between rupture length and event probability. Our findings support that geometrical complexity helps limit the size of large events and provide insights into the competition between energy supply and dissipation during rupture propagation.