Figure 2. 3D grid search of the M5.1 mainshock centroid location-time. (a) : Horizontal slice on the space-time correlation plot of trial centroid point sources at a depth of 12 km. The best result was obtained for source number 16 (the larger focal mechanism) with a correlation of 85% situated almost 4 km WNW of the hypocenter reported by IRSC (black star). (b) : Centroid time correlation plot for the preferred point source #16. The best centroid time has obtained 3.3 s after the IRSC reported origin time. (c) : Waveform-fit between the real (solid) and synthetic (dashed) displacements for the best obtained moment tensor. Station names-components are written on the top of each sub-figure. Gray waveforms were not used in the inversion, while the related synthetics were produced by forward modeling.