Mixed deformation styles observed on a shallow subduction thrust, Hikurangi margin, New Zealand
Mixed deformation styles observed on a shallow subduction thrust, Hikurangi margin, New Zealand
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DOI：
10.1130/g46367.1
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发表时间：
2019-09-01
期刊：
影响因子：
5.8
通讯作者：
LeVay, L.
中科院分区：
文献类型：
--
作者：
Fagereng, A.;Savage, H. M.;LeVay, L.
地球物理观测表明，在浅俯冲逆冲断层的断层滑动风格的空间和时间的变化，但地质特征和潜在的变形过程仍然知之甚少。国际海洋发现计划（IODP）第372和375次考察考察了新西兰的希库朗吉边缘，该地区经历了海啸地震和反复的缓慢滑动事件。我们报告的直接观测，采样的积极Papaku展断层在304米以下的海底。该断层扎根于板块界面，包括一个18米厚的主断层，其下有一个类似于30米的变形程度较低的下盘，以及一个类似于未变形下盘上方的10米厚的辅助断层。断层带结构包括角砾岩、褶皱和不对称碎屑，位于换位和/或肢解的、相对均匀的粉砂质半远洋沉积物中。资料表明，该断层经历了韧性和脆性变形。这种结构的变化表明，一系列的局部滑动速度可以发生沿着浅断层，它们是由时间，潜在的远场，应变率或有效应力的变化。
Geophysical observations show spatial and temporal variations in fault slip style on shallow subduction thrust faults, but geological signatures and underlying deformation processes remain poorly understood. International Ocean Discovery Program (IODP) Expeditions 372 and 375 investigated New Zealand's Hikurangi margin in a region that has experienced both tsunami earthquakes and repeated slow-slip events. We report direct observations from cores that sampled the active Papaku splay fault at 304 m below the seafloor. This fault roots into the plate interface and comprises an 18-m-thick main fault underlain by similar to 30 m of less intensely deformed footwall and an similar to 10-m-thick subsidiary fault above undeformed footwall. Fault zone structures include breccias, folds, and asymmetric clasts within transposed and/or dismembered, relatively homogeneous, silty hemipelagic sediments. The data demonstrate that the fault has experienced both ductile and brittle deformation. This structural variation indicates that a range of local slip speeds can occur along shallow faults, and they are controlled by temporal, potentially far-field, changes in strain rate or effective stress.