The role of dehydration reaction in seismogenic processes at subduction plate boundaries

在大约50-200km的中深度观测到的双地震带发生的一个流行的假设是蛇纹岩化的板块地幔的脱水脆化。蛇纹岩的弱化是由于蛇纹岩脱水反应引起的超孔隙流体压力所致。然而，这些使用气介质装置的实验的围压限制为500MPa（对应15km深度）。同样的机制是否能有效地在更高压力下俯冲板块，这是值得怀疑的。利用固-介质变形仪对蛇纹岩进行恒应变速率实验，发现蛇纹岩的屈服强度随着脱水反应的进行而急剧下降。这种被称为“脱水弱化”的现象将是理解蛇纹岩化地幔板块的孕震过程的关键。

A popular hypothesis for the occurrence of double seismic zones, observed at the intermediate depth of about 50-200km, is dehydration embrittlement of the serpentinized slab mantle. The weakening of serpentinite was attributed to excess pore fluid pressure caused by dehydration reaction of serpentine. However, the confining pressure of these experiments using gas-medium apparatus was limited up to 500MPa (corresponding to 15km depth). It is questionable if the same mechanism could be effective in subducting slabs at higher pressures. We conducted constant strain-rate experiments of serpentinite using a solid-medium deformation apparatus and found that the yield strength of serpentinites drastically decreased when dehydration reaction proceeded. This phenomena, named "dehydration weakening", would be a key to understand seismogenic processes in the serpentinized mantle slabs.