Localization algorithms for search and rescue applications

Detection of microseismic noise generated by survivors trapped by debris is a method already used by S&R teams. Present S&R equipment work exclusively on energy analysis while ignore information carried by propagation delays. We explore the potential of traveltime analysis compared to energy analysis for 2D and 3D localization. Results obtained on a couple of debris fields used for training S&R teams demonstrate that traveltimes are not less reliable than energy. A joint analysis of both the signal parameters can be an appropriate strategy to improve the 2D localization reliability. Besides, traveltimes can potentially extend the localization to the third dimension by returning an approximate estimate of the survivor depth. Main obstacles to achieve this goal are the inhomogeneity of the debris pile, the need of a real-time response, the limited extension of the sensor array. Despite of these difficulties, the preliminary results obtained in the fields with two different algorithms, one based on statistical traveltime inversion, the other based on data focusing, are encouraging and show accuracy in the limit of the seismic resolution. Both the algorithms are flexible and can be customized to face the peculiar constraints posed by this application.