Multistation infrasonic observations of the Chilean earthquake of 2005 June 13



On 2005 June 13, a major earthquake (M7.8) occurred in the Tarapaca region (North Chile), within the region of high mountains. At large distances from the epicentre, this event produced coherent infrasonic waves detected by three infrasound stations that are part of the International Monitoring System. The observed azimuth variations and the long signal durations suggest that wide regions in the Andes Mountains radiated infrasonic waves. From these observations, the main sources' regions are reconstructed. Such an event recorded by multiple stations offers an unique opportunity to evaluate the relative contributions of the different source mechanisms involved in large earthquakes as well as to improve our understanding of the amplification of ground displacement caused by the topography. With a review of infrasound signals from past earthquakes, extended empirical scaling relations are derived. We show that beyond the seismic magnitude, both seismic source and topographic features also play a predominant role in the generation of infrasound.