THE EFFECT OF GEOMETRICAL COMPLEXITY ON EARTHQUAKE RUPTURE LENGTH (Invited Presentation)

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 meters 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 earthquake gates influences surface rupture length, inferring an exponential relationship between rupture length and event probability for a given fault. Our findings support that earthquake gates limit the size of large events and help discriminate between different proposed models of rupture propagation.