Abstract
<title>Abstract</title> <p>Surface rupture displacement is a critical parameter controlling earthquake-related damage and fault-specific seismic hazard, yet its along-strike variability remains difficult to predict. Existing approaches commonly rely on empirical scaling relationships or prescribe heterogeneous stress and frictional conditions, leaving unresolved whether localized high-slip domains, or asperities, are fundamental consequences of earthquake physics or simply imposed model assumptions. Here we develop a physics-based framework in which asperity-like slip localization emerges naturally from the constraints imposed by seismic moment conservation and finite fault geometry. By coupling a moment-balanced truncated Gutenberg–Richter earthquake occurrence model with magnitude-dependent rupture scaling, we show that uniform slip distributions become unstable under a fixed moment budget, and localized slip domains arise as energetically preferred configurations without prescribing asperity locations or heterogeneous frictional patches. The framework reproduces the observed spatial organization of surface rupture displacement across 23 historical strike-slip earthquakes, capturing both segmented and throughgoing rupture patterns across diverse tectonic environments. Applications to the central San Andreas Fault and the Anninghe Fault further demonstrate that fault-specific displacement distributions can be predicted from fault geometry, slip rate, and seismic moment constraints alone. Our results reveal that asperity localization is not merely an inherited feature of fault heterogeneity, but an emergent property of finite fault systems. This provides a unified physical basis for predicting surface rupture displacement and improves the mechanistic understanding of earthquake rupture complexity and fault-specific seismic hazard.</p>