A relationship between giant earthquakes and core flow instabilities?

Abstract

Giant earthquakes of exceptional energy release induce large coseismic deformation field, with measured offsets of the order of millimeter recorded by GPS stations at distances of thousand kilometers from the epicenter. The recorded deformation field is just the surface expression of a volume deformation affecting the whole Earth. According to theoretical models of global coseismic deformation, the 2004 Sumatra-Andaman earthquake, which was the second-greatest occurred in the instrumental age, is expected to have affected the core-mantle boundary with static deformations of the order of millimeter over a large area. At the same time, high-resolution core magnetic-field models based on satellite observations evidenced a short-timescale geostrophic fluid acceleration at the top of the core. These anomalies are located in a region corresponding to the Indian ocean and occur in a time window containing the earthquake occurrence. More interestingly, the acceleration pattern is close to the modeled displacement due to earthquake coseismic effects. These evidences suggest us the possible existence of a relationship between giant earthquakes and rapid perturbations in the Earth core dynamics.