Earthquake magnitude is controlled by the rupture area of the fault network hosting the event. For surface-rupturing large strike-slip earthquakes (~MW6+), ruptures must overcome zones of geometrical complexity along fault networks. These zones, or earthquake gates, act as barriers to rupture propagation. We map step-overs, bends, gaps, splays, and strands from the surface ruptures of 31 strike-slip earthquakes, classifying each population into breached and unbreached groups. We develop a statistical model for passing probability as a function of geometry for each group. Step-overs, and single bends are more predictable earthquake gates than double bends and gaps, and ~20% of ruptures terminate on straight segments. Based on our modeled probabilities, we estimate event likelihood as the joint passing probabilities of breached gates and straight segments along a rupture. Event likelihood decreases inversely with rupture length squared. Our findings support a barrier model as a factor in limiting large earthquake size.