Differential contraction of subducted lithosphere layers generates deep earthquakes
Differential contraction of subducted lithosphere layers generates deep earthquakes
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DOI：
10.1016/j.epsl.2015.03.053
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发表时间：
2015-07
影响因子：
5.3
通讯作者：
Lijun Liu;J. S. Zhang
中科院分区：
文献类型：
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作者：
Lijun Liu;J. S. Zhang
引发深部地震的力量来源仍然难以捉摸。我们提出了一个新的力学模型，该模型考虑了板块下沉时在相变过程中由于不同体积变化引起的壳幔岩石圈之间积累的剪切应变的持续释放。这在板块内部产生了随深度增加的向下挤压，与深部地震震源机制的全球分布一致。利用实验标定的板坯流变学结果表明，估计的板坯内应力分布与冷板坯和暖板坯深部地震的深度-频率关系很好地吻合，∼600公里处的地震活动峰值对应于诱发应力的最大值。冷板中残余应力的这种机制也为发生在汤加西部和西班牙等前俯冲带下的深部地震提供了一种解决方案。我们进一步认为，这个模型可以调和现有的关于板片绝对强度、实验室和地球物理反演之间的地幔岩石强度差异以及地震发震应力和板片拉力之间的竞争的地球动力学悖论。
The origin of forces for generating deep earthquakes remains elusive. We propose a new mechanical model that involves constant release of shear strain accumulated between the crust and mantle lithosphere caused by differential volume changes during phase transformations as a slab sinks. This generates increasing down-dip compression inside the slab with depth, consistent with the global distribution of deep earthquake focal mechanisms. Using experimentally calibrated slab rheology, we show that the estimated distribution of slab internal stress agrees well with the depth–frequency relationship of deep earthquakes in both cold and warm slabs, with the peak in seismicity at ∼600 km depth corresponding to an induced stress maximum. This mechanism of residual stress within a cold slab also provides a solution to deep earthquakes occurring beneath former subduction zones such as western Tonga and Spain. We further suggest that this model may reconcile existing geodynamic paradoxes concerning the absolute strength of slabs, discrepancies on mantle rock strength between laboratory and geophysical inversions, as well as the competition between earthquake-generating stresses and slab-pull forces.