Forecasting the effects of the Andaman Islands - Sumatra megathrust earthquakes (Dec. 2004 and Mar. 2005) on volcanoes in the surrounding area

Abstract

The Andaman Islands - Sumatra earthquake (Mw = 9.3, Dec. 2004) and the subsequent Sumatra earthquake (Mw = 8.7, Mar. 2005) represent one of most energetic sequence of earthquakes ever recorded. Since both events occurred in a stronglyactive volcanic region, their exceptionally strong stress perturbation gives the opportunity to understand the effects of stress perturbations on volcanic systems.Here, we set the rules for a forward test of the causal relationship between stressperturbation and subsequent volcanic eruptions, by means of the comparison of the spatio-temporal distribution of the eruptions which follow the earthquakes with theco- and the post-seismic stress field due to the earthquakes. In practice, we forecast that the volcanic activity of the next 30 years will be significantly promoted by the stress perturbation; thus, we define the rules for an objective test of suchan hypothesis. Given the extremely high values of stress perturbation due to this sequence of earthquakes, the results of our test will definitively provide a reliable evaluation of the possible statistical impact of earthquake-eruption interaction onlong-term volcanic hazard assessments.