Scaling of the Source Dimensions of Interface and Intraslab Subduction-zone Earthquakes with Moment Magnitude

Abstract

This paper derives source scaling relations between rupture dimensions and moment magnitude for subduction-zone earthquakes, separating between interface events occurring at the contact of the subducting and overriding tectonic plates, and intraslab events, which occur within the subducting slab. These relations are then compared with existing scaling relations, which are predominantly based on data from crustal events. Relations between the dimensions of the rupture zone of earthquakes and the amount of energy released as measured by the seismic moment, M , or equivalently moment magnitude, Mw , (Hanks and Kanamori 1979), are of great practical use in engineering seismology. Early relations ( e.g. , Kanamori and Anderson 1975; Wyss 1979) were derived with the purpose of using rupture dimensions to constrain estimates of magnitude. Additionally, the relation between independently determined rupture dimensions and seismic moment also was used to draw inferences in terms of source scaling from comparisons between observed data and predictions of theoretical seismological models ( e.g. , Kanamori and Anderson 1975; Astiz et al. 1987). Nowadays, moment magnitude is routinely estimated from instrumental recordings, and the scaling relations described above are predominantly used to infer the probable dimensions of an earthquake of given magnitude. Applications include distance calculations using finite-fault distance metrics ( e.g. , Chiou and Youngs 2006), characterization of seismic sources in seismic hazard analysis, and theoretical studies involving forward-modeling of fault slip and resulting ground motions ( e.g. , Atkinson and Macias 2009; Somerville et al. 2008). However, the reciprocal relations giving moment magnitude as a function of rupture dimensions may still be useful for estimating the moment magnitude of either historical or hypothetical scenario events for which an estimate of the rupture dimensions is available, for instance on the basis of the dimensions of an observed seismic gap or from fault …