高温高压下矿物流变强度与深源地震机制

利用高压原位同步辐射X射线衍射和衍射谱宽的分析，测量了地幔主要矿物橄榄石（olivine, α相）、卫思里石(wadsleyite，β相）、林伍德石(ringwoodite，γ相)及钙钛矿相(perovskite)高温高压下的流变强度.实验结果证明,上地幔和过渡层的矿物与下地幔矿物有非常不同的特点.橄榄石、β相和γ相的流变强度都对温度十分敏感，但唯有橄榄石强度在相对低温时就显著减弱，在873K时，橄榄石的强度只有β相的三分之一.与此相反，钙钛矿相的流变强度对温度的敏感度极低.地幔主要矿物流变强度（即矿物积累应力的能力）的特征及其对温度的敏感性可以帮助解释深源地震的发生频率随深度变化的规律.

Rheology of mantle minerals at high pressure and high temperature,and its influence on deep earthquakes

The rheological strengths of the major minerals in the Earth's mantle have been measured using in situ synchrotron X-ray diffraction at high pressures and high temperatures. Deconvolution of the diffraction peak widths is used to derive the yield strengths. The experiments indicate that minerals in the upper mantle and transition zone have a very different rheological character from the lower mantle minerals. The strengths of olivine, wadsleyite and ringwoodite are very sensitive to temperature, and that of olivine is weakened significantly more than for wadsleyite and ringwoodite at relatively low temperatures, being only about 1/3 wadsleyite’s strength at 873 K. In contrast, the strength of perovskite is very insensitive to temperature. The characteristics of rheological strength, i.e. stress accumulation capability and temperature dependence, may play a crucial role in defining the profile of deep earthquake occurrence as a function of depth.