Figure 2. The distance coverage of the data available for events of groups A to D. For each event the source spectra retrieved from LVIG and, if available, from PNIG (marked by filled circles and triangles, respectively) are compared with the median spectrum obtained from all other stations of Mexican seismological and accelerometric stations (shown by open circles). Group A and C events provide an estimate of Q of the mantle wedge. Station SCIG is marked by filled rectangles in the figure.