Abstract

Multiple, widely spaced, infrasonic arrays are routinely used to detect and localize impulsive events of unknown origin at medium ranges (<100 km). Event data are subsequently processed to yield line of bearing (LOB) information and localization is accomplished manually. This method of analysis could significantly benefit from automatic association and localization. Because infrasound arrays are often separated by many tens of kilometers and signals reaching the arrays can be significantly altered along the propagation path, the task of associating signals is difficult and time consuming. Further, confidence in an event association is difficult to assign to a signal due to arrival timing and local interferers. By using beamforming methods and coherence between signals, it is possible to automatically associate a given recorded event. At each array, a delay and sum beamformer is used to calculate the LOB to an unknown source. The delayed and summed beam at each array is then used to calculate the pairwise coherence between all beams. Impulsive events due to sources recorded by widely spaced infrasound arrays often exhibit high coherence at many of the frequencies in the signal. Examples of successful associations between widely spaced arrays will be discussed.

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