Figure 3

Photographs of paleoearthquake ruptures showing a westward bifurcation and change in geometry and kinematics close to the surface at Byeokgye and Inbo1 trench sites. (a) A photograph at Byeokgye site on the main fault core (modified from Song et al.²⁶) and (b) a close-up view of fault splays. Note that the fault splays have N–S to NW–SE-strikes with low-angle dips in the unconsolidated strata. (c,d) Photographs at Inbo1 site on the subsidiary fault (modified from Cheon et al.²⁸). The first small trench (d) was extended to the ~ 8 m deep, ~ 20 m long deep trench (c). White circles indicate the rupture termination locations. Insets in (a) and (c) show that fault striations observed in the unconsolidated strata. These striations predominantly show dextral-slip with a component of reverse movement. Straight arrows and dashed line indicate the movement direction of the missing blocks and the strike of the fault surfaces, respectively.