Fig. 3: Distributions of T and P axes and P axis plunge of optimal focal mechanism solutions and ΔCFS.

a T (tension) axes of aftershocks located at depths of 5 ± 0.5 km projected onto the horizontal plane. Their plunges (i.e., angles measured from the horizontal) are indicated by colours from blue to red. The inset figure indicates the T axis on a focal mechanism solution. b P (pressure) axes. c P axis plunges; showing that normal faulting events have larger plunges. d Distributions of ΔCFS for normal faulting aftershocks with a fault strike of N110°E, a plunge of 45°, and a slip direction of −90°. The grey and white beach balls of focal mechanism solutions indicate the orientations of T and P axes in (a) and (b). The inset rectangle in (d) indicates the fault plane on which ΔCFS is calculated. The upper edge and slip direction are shown by the bold line and arrow. Red and white lines indicate the estimated fault planes at this depth. The northern edge of the WF was set at Y = 6.1 km in this figure.