4. Discussion and conclusions
Simultaneous rupturing of the subduction interface and its splay faults (Fig. 6) explains the highly-segmented uplift pattern along the coast, which may result from the slip partitioning among the high-dipping angle splay faults (Fig. 6). During the earthquake, the block bounded by two fault systems parallel to the coast was likely squeezed out by the oblique westward slip south of the Kekerengu fault (Fig. 2a). When the mini-block south of the Jordan Thrust fault and the upper Kowhai fault was extruded by the westward motion (Figs. 2a and 6), the slip was partitioned into uplifting and southeastward motion between the Kaikoura ¯ Peninsula and the Papatea fault (Fig. 2a). By contrast, the region near the Hope fault shows minor horizontal motion, but only uplifting to the south. This is because of the nearly fault-perpendicular updip thrust along its subvertical fault plane. The southward motion between the Papatea and Kekerengu Faults can be explained by the shallow northwest-dipping (∼45◦) of the Jordan Thrust fault during the extrusion, but it can be alternatively interpreted as a result of thrust faulting occurred offshore (Clark et al., 2017). Distinguishing these two kinds of models will need evidence from seafloor surveys after the earthquake. The vertical coastal displacement pattern demonstrates that geomorphological features in a single event, such as stepped river terraces, can be overprinted on smooth vertical displacement produced by slip on the subduction interface. Such overprinted deformation driven by aforementioned simultaneous rupture slip within a complex multi-splay fault system will significantly change how the coastal uplift rate is interpreted.
