Infrasound associated with the 2004 Sumatra megathrust earthquake and tsunami

Abstract

Multiple infrasound arrays in the Pacific and Indian Oceans that are part of the International Monitoring System (IMS) observed three distinct waveform signatures associated with the December 26, 2004 Sumatra earthquake and tsunami. Infrasound station in Palau, Diego Garcia, Madagascar, and Kenya observed (1) seismic arrivals (P, S and surface) from the earthquake, (2) T-phases, propagated along SOFAR channel in the ocean, and coupled back to the ground, and (3) infrasonic arrivals associated with either the tsunami generation mechanism or the motion of the ground above sea level. All signals were recorded by the pressure sensors in the arrays. The seismic and T-phase recordings are due to the sensitivity of the MB2000 microbarometers to ground vibration, whereas the infrasound arrivals correspond to dispersed acoustic waves propagated through atmospheric waveguides. It appears that the arrival of the tsunami, as well as oceanic infragravity waves following the tsunami, were not observed by the infrasound stations. We show the prominent features of the arrivals, present source location estimates, discuss the absence of a signal associated with the tsunami arrival, and consider the potential for using infrasound as a discriminant for tsunami genesis.