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Calibrating the marine turbidite palaeoseismometer using the 2016 Kaikōura earthquake
Nature Geoscience ( IF 18.3 ) Pub Date : 2021-03-04 , DOI: 10.1038/s41561-021-00692-6
Jamie D. Howarth , Alan R. Orpin , Yoshihiro Kaneko , Lorna J. Strachan , Scott D. Nodder , Joshu J. Mountjoy , Philip M. Barnes , Helen C. Bostock , Caroline Holden , Katie Jones , M. Namik Cağatay

Turbidite palaeoseismology has produced arguably the most comprehensive multimillennial scale records of subduction-zone earthquakes but is underpinned by techniques that are vigorously debated in earthquake science. Resolving this argument requires new direct observations that test the approach’s essential assumptions. Here we present measurements from turbidites triggered by the 2016 Mw 7.8 Kaikōura earthquake in New Zealand, one of the most well-instrumented earthquakes in history. This natural experiment provides an ideal test for turbidite palaeoseismology because fault source, ground motions and turbidite deposition in discrete canyons are well-resolved by analysis of sediment cores combined with physics-based ground-motion modelling. We find that the Kaikōura earthquake triggered flows in ten consecutive canyon–distributary systems along a 200 km segment of the Hikurangi subduction margin where long-period (>2 s) peak ground velocities exceeded turbidity-current-triggering thresholds between 16–25 cm s−1. Comparison between ground motions and turbidite deposition confirm that there is a predictable relationship between earthquake source, ground motions and deposition of coseismic turbidites. We demonstrate that the patterns of triggering and resultant turbidite character may preserve evidence of fault-rupture direction along with the radiating patterns and amplification of earthquake ground motions.



中文翻译:

使用 2016 年凯库拉地震校准海洋浊积岩古地震仪

浊积古地震学已经产生了可以说是俯冲带地震最全面的千年尺度记录,但其基础是地震科学中激烈争论的技术。解决这个论点需要新的直接观察来测试该方法的基本假设。在这里,我们展示了由 2016 M w触发的浊积岩的测量结果新西兰发生 7.8 级凯库拉地震,这是历史上仪器最齐全的地震之一。这个自然实验为浊积岩古地震学提供了理想的测试,因为断层源、地震动和离散峡谷中的浊积岩沉积通过沉积岩心分析结合基于物理的地震动建模得到了很好的解决。我们发现,Kaikōura 地震触发了沿 Hikurangi 俯冲边缘 200 公里段的 10 个连续峡谷 - 分流系统的流动,其中长周期(> 2 秒)峰值地面速度超过了 16-25 厘米 s 之间的浊度电流触发阈值-1. 地震动与浊积岩沉积的比较证实,震源、地震动与同震浊积岩沉积之间存在可预测的关系。我们证明了触发模式和由此产生的浊积岩特征可以保留断层破裂方向的证据以及地震地面运动的辐射模式和放大。

更新日期:2021-03-04
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