Do trench sediments affect great earthquake occurrence in subduction zones?
Do trench sediments affect great earthquake occurrence in subduction zones?
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海沟沉积物是否影响俯冲带大地震的发生？
DOI：
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发表时间：
1989
期刊：
影响因子：
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通讯作者：
L. Ruff
中科院分区：
文献类型：
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作者：
L. Ruff
地震能量的释放以俯冲带的俯冲地震为主，并进一步集中在少数俯冲带。有些俯冲带以发生大地震为特征，而另一些则相对平静。俯冲带之间最大地震规模的变化是全球地震活动的最重要特征之一。以前的工作表明，最大地震规模的变化与俯冲带的其他两个性质的变化有关：俯冲岩石圈的年龄和收敛速率。这两个性质并不能解释最大地震规模的所有变化。我认为俯冲带的第三个特性，“海沟沉积物”，解释了最大地震规模剩余差异的一部分。俯冲带可分为两类：（1）有过量海沟沉积物的俯冲带;（2）海沟处有地垒和地堑结构的俯冲带。在19个最大的俯冲带事件中，有13个（包括3个最大的）发生在海沟沉积物过多的区域。约有一半的海沟沉积物过剩带具有发生大地震的特征。其他大部分海沟沉积物过剩但没有大地震的地区，根据年龄-速率相关性预测将有小地震发生。两个值得注意的例外是俄勒冈州-华盛顿州和中美洲地区。总的来说，过量海沟沉积物的存在似乎会增强大地震的发生。一种推测性的物理机制将海沟沉积物与地震规模联系起来，即过量的海沟沉积物与一个连贯的沉积层的俯冲有关，该沉积层在高温高压下在板块之间形成一个均匀而牢固的接触区。
Seismic energy release is dominated by the underthrusting earthquakes in subduction zones, and this energy release is further concentrated in a few subduction zones. While some subduction zones are characterized by the occurrence of great earthquakes, others are relatively aseismic. This variation in maximum earthquake size between subduction zones is one of the most important features of global seismicity. Previous work has shown that the variation in maximum earthquake size is correlated with the variation in two other subduction zone properties: age of the subducting lithosphere and convergence rate. These two properties do not explain all the variance in maximum earthquake size. I propose that a third subduction zone property, “trench sediments”, explains part of the remaining variance in maximum earthquake size. Subduction zones are divided into two groups: (1) those with excess trench sediments, and (2) those with horst and graben structure at the trench. Thirteen of the 19 largest subduction zone events, including the three largest, occur in zones with excess trench sediments. About half the zones with excess trench sediments are characterized by great earthquake occurrence. Most of the other zones with excess trench sediments but without great earthquakes are predicted to have small earthquakes by the age-rate correlation. Two notable exceptions are the Oregon-Washington and Middle America zones. Overall, the presence of excess trench sediments appears to enhance great earthquake occurrence. One speculative physical mechanism that connects trench sediments and earthquake size is that excess trench sediments are associated with the subduction of a coherent sedimentary layer, which at elevated temperature and pressure, forms a homogeneous and strong contact zone between the plates.