Characteristics of focal mechanisms in Chile subduction

Abstract: We use the Centroid Moment Tensor (CMT) solution of the earthquakes occurred in Chile subduction to analyze the characteristics of focal mechanisms. We define the angle between P, B, and T axes of focal mechanisms and three stress axes of tectonic stress field as the consistency parameter, to research the dynamic changes of focal mechanism pattern in earthquake preparation area before the 2010 Maule, Chile earthquake. The result shows that the consistency parameter decreases before the earthquake, and the area of the lower consistent parameter visually coincides with the distribution of aftershocks. This phenomenon is similar to the Load-Unload Response Ratio (LURR) decreases prior to the occurrence of macro-fracture happened in the acoustic emission experiments involving large rock specimens under tri-axial stress.