Transformation-induced faulting requires an exothermic reaction and explains the cessation of earthquakes at the base of the mantle transition zone
Transformation-induced faulting requires an exothermic reaction and explains the cessation of earthquakes at the base of the mantle transition zone
复制标题
转变引起的断层作用需要放热反应，并解释了地幔过渡带底部地震的停止
DOI：
10.1016/0040-1951(95)00164-6
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发表时间：
1996
期刊：
影响因子：
2.9
通讯作者：
Yi Zhou
中科院分区：
文献类型：
--
作者：
H. Green;Yi Zhou
在许多俯冲带中，地震持续发生到地幔过渡带的底部，并在标志着下地幔顶部的吸热相变处突然停止，这表明了因果关系。对钛铁矿参与钙钛矿相变的多晶体的新实验表明，相变诱导的断层只发生在反应的放热方向。密切的结构和热力学之间的相似性的转换研究在这里CdTiO 3和那些预期在地球地幔的硅酸盐强烈认为，这些结果是相关的俯冲岩石圈中发生的转变。此外，考虑这种不对称性的热力学表明，这一结果应该是一个普遍的现象。如果是这样的话，那么这种机制的断层作用就不会发生在下地幔，这就为地震在700公里深度之前终止提供了一个自然的解释。如果一个“楔”含有亚稳橄榄石存在于俯冲带的深度，是必要的深地震，我们的研究结果删除的约束，这个“楔”必须锥形为零，最深的地震发生。1994年深源大地震及其余震的特征表明，深源地震可以传播到原震源区以外，并在那里触发余震，这为深源地震的机制提供了重要的新信息，并指出需要进行更多的实验。
In many subduction zones, earthquakes occur continuously to the bottom of the mantle transition zone and stop abruptly at the endothermic phase change marking the top of the lower mantle, suggesting cause and effect. New experiments on polycrystals undergoing the ilmenite ↔ perovskite transformation show that transformation-induced faulting occurs only in the exothermic direction of the reaction. The close structural and thermodynamic analogies between the transformation studied here in CdTiO3and those expected in the silicates of the earth's mantle argue strongly that these results are relevant to transformations occurring in subducting lithosphere. Moreover, consideration of the thermodynamics of this asymmetry show that this result should be a general phenomenon. If so, it follows that faulting by this mechanism cannot occur in the lower mantle, providing a natural explanation for the termination of earthquakes just before 700 km depth. If a ‘wedge’ containing metastable olivine exists at depth in subduction zones and is necessary for deep earthquakes, our results remove the constraint that this ‘wedge’ must taper to zero where the deepest earthquakes occur. The characteristics of the large deep earthquakes of 1994 and their aftershocks show that deep earthquakes can propagate beyond the zone of previous hypocenters and trigger aftershocks there, providing important new information about the mechanism of deep earthquakes and pointing to the need for additional experiments.