Characteristic Features of Intraplate Earthquakes and the Models Proposed to Explain Them

Abstract

An evaluation of various aspects of intraplate earthquakes (IPE) suggests that they occur by reactivation of a variety of pre-existing features in response to the current stress field. In this review, I first list the various methods of identifying these features, and then describe the characteristic elements of IPE. Reactivation occurs by one or more of three ways. These include a localized build-up of stress on the potentially seismogenic feature due to the ambient stress field, the superposition of a triggering stress and the reduction of strength of the feature(s) by mechanical and/or chemical means. The various models that have been suggested to explain IPE contain one or more of these elements.

Models in the first category include stress amplification near plutons, the initiation and termination of seismicity at fault bends, the concentration of stress at intersections of seismogenic features, and stress build-up on faults due to localized strain in the mid-lower crust. In the second category are triggering stresses due to glacial rebound and due to lateral variations in the density. In the third category, which is an extension of the mechanism of reservoir induced seismicity to subcrustal depths, failure occurs by the reduction of strength of rocks by mechanical or chemical means. This is the hydroseismicity model. Of all the models, I prefer the intersection model.