两相矿物蠕变:探讨俯冲带深源地震机制

Creep of two-phase minerals:Investigating mechanism of deep earthquakes in subduction zones

本文利用数值模拟方法研究了橄榄石-单斜辉石、瓦兹利石-单斜辉石、林伍德石-石榴石三种两相矿物模型在俯冲带温度应力条件下的蠕变,分析了剪切应力在俯冲带两相矿物模型中的发展,结果显示矿物蠕变差异在俯冲带剪切应力发展过程中起到了重要作用.尤其是林伍德石的快速蠕变率及其与石榴石的蠕变差极大地加速了俯冲带剪切应力的发展过程,可能是600km深度附近地震数量急剧增多的重要原因.我们的结果可以从一个新的角度理解俯冲带深源地震机制.

In this study, we investigated the shear stress development during creep of two-phase mineral models in subduction zones using the numerical simulation method. Three models were used： olivine-clinopyroxene, wadsleyite-clinopyroxene and ringwoodite-garnet. The results show that the rheological contrast between phases plays a very important role in the shear stress development of the subduction zone. Especially, the fast strain rate of ringwoodite and the rheological contrast between ringwoodite and garnet largely accelerate the shear stress development in the subduction zone. That may help to explain the increase of earthquake number at around 600 km depth in the subduction zone. Our results provide a new insight into the mechanism of deep earthquakes.