Subevent structure of large earthquakes—A ground‐motion perspective

Abstract

Our ability to predict ground motions from future earthquakes hinges on the accurate modeling of the radiation from the earthquake source. A successful approach to modeling earthquake radiation has been to represent faults as a series of discrete, independently‐rupturing subfaults, although their physical interpretation has remained largely unclear. Our simulation of ground motions from twenty‐six well‐recorded moderate‐to‐large earthquakes substantiates the hypothesis that large ruptures are made up of a sequence of smaller subevents. The size of a subevent follows a simple linear relationship with the size of the earthquake fault in an apparently deterministic manner. The strength of the high‐frequency radiation is controlled by the maximum slip velocity, which varies stochastically over a small range. Both the characteristic subevent size and the slip velocity appear to be region‐independent, indicating a remarkable uniformity in earthquake source properties. This observation helps to reduce the uncertainty in ground‐motion prediction by constraining its essential and previously ambiguous parameters.