ABSTRACT

The north-striking sinistral reverse Papatea Fault ruptured with a very large (up to 12 m) oblique slip as part of the 2016 M_W 7.8 Kaikōura earthquake in the northeastern South Island. Paleoseismic studies were undertaken at three sites along the Papatea Fault, named Murray’s roadcut, Jacqui’s Gully (both on the main strand), and Wharekiri trench (western strand). These sites provide evidence for up to three Late Holocene paleoearthquakes prior to 2016 (=E₀) on this previously unmapped active fault, with preferred OxCal-modelled timings of 98–149 (E₁), 546–645 cal yr BP (E₂), and >738 cal yr BP (E₃). Event correlations between the sites are generally consistent across these past events, implying that the two strands of the Papatea Fault link at depth and rupture together co-seismically as in 2016. Comparisons of its paleoseismic record with the Kekerengu Fault and uplift data from Waipapa Bay and Kaikōura, suggest that the Papatea Fault may have three distinct rupture modes: (i) Kaikōura-type multi-fault ruptures with multi-metre, anelastic block displacements and associated major landscape change; (ii) multi-fault earthquake ruptures with other regional fault combinations; and (iii) single-fault Papatea ruptures with metre-scale displacement. OxCal models offer the possibility that the E₁ fault rupture occurred in 1855 CE.

摘要

作为南岛东北部2016 _MW 7.8 Kaikōura地震的一部分，北向左旋逆向 Papatea 断层破裂并产生非常大（高达 12 m）的倾斜滑动。古地震研究在 Papatea 断层沿线的三个地点进行，分别是 Murray's roadcut、Jacqui's Gully（均位于主链）和 Wharekiri 沟槽（西链）。_{这些站点提供了在 2016 年之前（=E 0}）在这个以前未映射的活动断层上发生多达三个晚全新世古地震的证据，首选 OxCal 建模时间为 98-149（E ₁），546-645 cal yr BP（E ₂ ), >738 cal yr BP (E ₃). 这些地点之间的事件相关性在这些过去的事件中通常是一致的，这意味着 Papatea 断层的两条链在深度上连接在一起并像 2016 年一样同震破裂。其古地震记录与 Kekerengu 断层的比较以及 Waipapa 湾的隆起数据和 Kaikōura，表明 Papatea 断层可能具有三种不同的破裂模式：(ii) 与其他区域断层组合的多断层地震破裂；(iii) 单一断层 Papatea 断裂，位移为米级。_{OxCal 模型提供了 E 1}断层破裂发生在公元 1855 年的可能性。