Slow slip along the Hikurangi margin linked to fluid-rich sediments trailing subducting seamounts
Slow slip along the Hikurangi margin linked to fluid-rich sediments trailing subducting seamounts
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DOI：
10.1038/s41561-023-01186-3
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发表时间：
2023-06-05
影响因子：
18.3
通讯作者：
Fry, Bill
中科院分区：
文献类型：
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作者：
Bangs, Nathan L.;Morgan, Julia K.;Fry, Bill
大型海山和基底起伏在俯冲带与上覆板块碰撞时造成永久变形。由此产生的结构和成分的不均匀性已被牵连的控制因素在巨型逆冲断层滑动行为。俯冲海山可能暂时锁定板块，有利于随后的大地震。或者，海山可能重新分布应力，减少地震滑动。在这里，我们提出了三维地震数据，从海底镶嵌俯冲希库朗吉高原沿着新西兰北岛。我们发现，一个成像良好的海山，Papaku海山，局部隆起的覆盖板，并留下一个管状的透镜的沉积物尾随其尾流。Papaku透镜内部和下方以及沿着巨型逆冲断层的异常低地震速度与未固结、超压的富含流体的沉积物的存在相一致。从一个较老的沉积物透镜（对应于2014年的一个缓慢滑动破裂事件的位置）获得的类似观测结果表明，由于俯冲板块的排水延迟，这种超压可能会沿着巨型逆冲断层持续存在。2014年慢滑地震与这种沉积物透镜的搭配表明，这些富含流体的区域定义了能够缓慢滑动的区域。我们假设，沉积物透镜体留下的俯冲海山可以创建低有效应力补丁内过渡稳定的海洋沉积物沿着的megahutch，有利于缓慢slipp.Sediment透镜体尾随俯冲海山可以保持持久的流体压力，并支持在沉积物丰富的俯冲带的慢滑行为，根据三维地震调查的希库朗吉边缘。
Large seamounts and basement relief cause permanent deformation when they collide with the overriding plate at subduction zones. The resulting structural and compositional heterogeneities have been implicated as controlling factors in megathrust slip behaviour. Subducting seamounts may temporarily lock plates, favouring subsequent large earthquakes. Alternatively, seamounts may redistribute stress, reducing seismic slip. Here we present three-dimensional seismic data from the seamount-studded subducting Hikurangi Plateau along New Zealand's North Island. We find that one well-imaged seamount, the Papaku Seamount, locally uplifts the overriding plate and leaves a tube-shaped lens of sediment trailing in its wake. Anomalously low seismic velocities within and below the Papaku lens and along the megathrust fault are consistent with the presence of unconsolidated, overpressured fluid-rich sediments. Similar observations from an older sediment lens, which corresponds to the location of a 2014 slow-slip rupture event, suggest that such overpressures can persist along the megathrust due to delayed drainage out of the subducting plate. The collocation of the 2014 slow-slip earthquake with this sediment lens suggests that these fluid-rich regions define zones that enable slow slip. We hypothesize that sediment lenses left behind by subducting seamounts can create low-effective-stress patches within transitionally stable marine sediment along the megathrust that are conducive to slow slip.Sediment lenses trailing subducting seamounts could maintain long-lasting fluid pressures and support slow-slip behaviour at sediment-rich subduction zones, according to three-dimensional seismic surveys of the Hikurangi margin.