Extended Data Figure 2: Source time history and rupture velocity estimation from backprojection of high frequency teleseismic waves.

a, b, Time history of the peak semblance at each time frame (blue) (a) and the corresponding energy (red, arbitrary units) for the mainshock (left) and the Iquique aftershock (right) (b). Energy integrated over the whole grid is plotted as a black line. Whereas the red curves describe the energy time history of one (the principal) radiating point, the black lines take into account the seismic energy emitted from the whole source area. The time axis represents the central point of the sliding windows 8 s long; that is, the first onset of the event will affect the energy and semblance at nominal times up to 4 s before the physical onset of rupture. The semblance and energy peak at ∼160 s corresponds to an early aftershock. The area of the diamonds of Fig. 2b is scaled to the energy (red curves) shown in b (only solutions with semblance higher than 0.05 are shown in Fig. 2b). c, Distance of maximal semblance peaks to a reference profile (transects 1 and 2 for the mainshock (left) and the aftershock (right), respectively, plotted in Supplementary Videos 3 and 4). The figure is zoomed in the downdip migrations of the rupture fronts (about 0–30 s). The accelerated propagation can be identified in the interval 15–30 s. The area of the circles is scaled to the energy of the semblance maxima (red curves in b).