Earthquake size distribution in subduction zones linked to slab buoyancy
Earthquake size distribution in subduction zones linked to slab buoyancy
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DOI：
10.1038/ngeo2279
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发表时间：
2014-12
影响因子：
18.3
通讯作者：
T. Nishikawa;S. Ide
中科院分区：
文献类型：
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作者：
T. Nishikawa;S. Ide
俯冲带地震的发生主要受俯冲板块和上覆板块之间界面上的应力状态控制。这种应力状态受到构造特性的影响，例如俯冲板块的年龄和板块运动的速率,,,。直接测量板界面上的应力是很困难的。然而，可以使用古腾堡-里希特关系的 b 值来推断应力状态，该值表征了小地震与大地震相比的相对数量，并且与差异应力负相关,,,,,,,。即，大地震相对频繁的俯冲带具有低b值和高应力状态。全世界俯冲带的 Theb 值差异很大，但这种差异的来源尚不清楚。在这里，我们利用先进的国家地震系统地震目录估算了全球不同俯冲带的88个剖面的b值，并将b值与俯冲板块的年龄和板块运动进行了比较。 b值与俯冲板块年龄呈正相关，因此板片较年轻的俯冲带更容易发生大地震，但b值与板块运动没有相关性。鉴于较年轻的板片温度更高、浮力更大，我们认为板片浮力是俯冲带应力状态和地震规模分布的主要控制因素。
The occurrence of subduction zone earthquakes is primarily controlled by the state of stress on the interface between the subducting and overriding plates. This stress state is influenced by tectonic properties, such as the age of the subducting plate and the rate of plate motion,,,. It is difficult to directly measure stress on a plate interface. However, the stress state can be inferred using the Gutenberg–Richter relationship’sb-value, which characterizes the relative number of small compared to large earthquakes and correlates negatively with differential stress,,,,,,,. That is, a subduction zone characterized by relatively frequent large earthquakes has a lowb-value and a high stress state. Theb-value for subduction zones worldwide varies significantly,, but the source of this variance is unclear. Here we use the Advanced National Seismic System earthquake catalogue to estimateb-values for 88 sections in different subduction zones globally and compare theb-values with the age of the subducting plate and plate motions. Theb-value correlates positively with subducting plate age, so that large earthquakes occur more frequently in subduction zones with younger slabs, but there is no correlation betweenb-value and plate motion. Given that younger slabs are warmer and more buoyant, we suggest that slab buoyancy is the primary control on the stress state and earthquake size distribution in subduction zones.