ABSTRACT

Retro-deformation of horizontal and vertical displacements is used to reconstruct the evolution of the South Island plate boundary faults since the Late Miocene. Finite dextral offset across the Alpine Fault is estimated from a system of N-S reverse faults displaced from Otago to the Glenroy-Matakitaki area, where the N-S tectonic trends are generally interpreted as a ‘bend’ of the Alpine Fault. Increasing dextral offset on the Alpine Fault was accompanied by a NE-migrating wave of exhumation and uplift of its hanging wall, tracked by syntectonic terrestrial deposits. Strike-slip and dip-slip components both decrease near the ‘bend’, where deformation is transferred to the Wairau and Marlborough faults. The Wairau Fault offsets dextrally by c. 50 km the N-S faults of the Glenroy-Matakitaki area, correlated with the Waimea-Flaxmore Fault System of Nelson. Finite dextral separation along the Alpine Fault is 410 km, and the N-S ‘bend’ is interpreted as a transpressive stepover between the Alpine and the Wairau faults. The lack of connection between the Alpine and Wairau faults, combined with slip transfer to the Hope Fault over the last 2 Myr, do not favour propagation of coseismic rupture from the Alpine Fault to the Wairau Fault across the ‘bend’.

摘要

水平和垂直位移的逆向变形被用来重建晚中新世以来南岛板块边界断层的演化。跨越高山断层的有限右旋偏移是根据从奥塔哥向 Glenroy-Matakitaki 地区位移的 NS 反向断层系统估计的，其中 NS 构造趋势通常被解释为高山断层的“弯曲”。高山断层右旋偏移量的增加伴随着北东向移动的折返波和其上盘的隆起，由同构造陆地沉积物追踪。走滑和倾滑分量都在“弯曲”附近减少，变形转移到 Wairau 和 Marlborough 断层。Wairau 断层向右偏移 c。Glenroy-Matakitaki 地区的 NS 断层 50 公里，与尼尔森的威美亚-弗拉克斯莫尔断层系统相关。沿 Alpine 断层的有限右旋分离为 410 公里，NS 的“弯曲”被解释为 Alpine 和 Wairau 断层之间的地压式跨步。Alpine 和 Wairau 断层之间缺乏连接，加上过去 2 Myr 滑移转移到 Hope 断层，不利于同震破裂从 Alpine 断层跨过“弯曲”传播到 Wairau 断层。