| This application implements a location procedure which allows imaging the distribution of seismic sources in both time and space. First, a characteristic function (CF; in this case, the STA/LTA ratio) is calculated at all the vertical-component seismograms from the selected stations. The user then define a volume likely containing the source(s), and a number of grid nodes along the two horizontal (NS-EW) and vertical coordinates for discretising this volume. For each grid node located at the arbitrary location (x,y,z), the predicted arrival times are calculated at all the stations, and the different CFs are time-shifted consequently. By stacking these time-shifted CFs one obtains a time-dependent Brightness function associated with that particular grid node. The procedure is iterated over all the grid nodes of the source volume; at the end of the process, the maximum (maxima) of the Brightness function will provide an estimate of the source location and origin time. The main advantage of this procedure is that it exploits waveform information (both arrival times and relative amplitudes) without the need of pre-assembled phase-picking data. The method, therefore, is particularly well-suited for emergent signals and/or for real-time applications. The technique has been largely inspired by the previous works from Kao and Shan (2004), Grigoli et al. (2013, 2014), Langet et al., (2014), to which the reader is referred for a more comprehensive description of the methodology. |