新西兰Hikurangi俯冲带孔隙流体来源和水岩作用示踪研究：对流体活动和慢滑移事件的指示

近十几年由于密集的全球定位系统观测网的布设，在全球很多俯冲带都发现有慢滑移事件的发生。俯冲带慢滑移事件作为一种重要的断层滑动方式，成为地震学新兴和前沿的研究领域。由于在许多俯冲带大地震之前都观测到慢滑移事件，故其对于预测地震和海啸及其风险评估有重要意义。尽管有研究认为板片脱水和流体活动导致的高孔隙流体压力是慢滑移事件形成的主要原因，但均是基于地震剖面成像和理论模拟等间接证据，关于板片脱水和流体活动与慢滑移事件的关系仍然不太清楚。本项目拟从全球范围慢滑移事件记录最好、源区深度最浅的新西兰Hikurangi俯冲带三个IODP站位的孔隙流体和沉积物入手，运用氢、氧、锂、锶同位素示踪的研究手段，揭示主要的水岩反应过程，确定孔隙流体来源和深度，刻画从俯冲板块到上覆板块的水文地质特征，探讨板片脱水和流体活动与慢滑移事件的关系，为阐明俯冲带慢滑移事件的成因机制提供重要参考。

Since the advent of dense geodetic networks in the last decade, a large number of slow slip events (SSEs) have been discovered at subduction megathrusts worldwide. They have been recognized as a significant model of fault slip, which has become burgeoning research frontier in seismology. As SSEs are often detected prior to large earthquakes on subduction zones, they have significant implication for predicting earthquakes and associated tsunamis. A number of studies have suggested that the development of SSEs is associated with high fluid pressure induced by slab dehydration and fluid flow. However, these hypothesized mechanisms for SSE occurrence are based largely on indirect evidences of geophysical mapping and theoretical modeling; the relationship between slab dehydration and SSEs remains a mystery. We propose to analyze the δ18O、δD、87Sr/86Sr、δ7Li of pore fluids and sediments retrieved from the three drilling sites of IODP Expedition 375 on the Hikurangi margin where SSEs are the most well-documented with the shallowest source area worldwide. Our main aims are to trace the sources of pore fluids, to understand the major water-rock interaction, to characterize the hydrogeology from the subducting plate to the upper plate, and to investigate the potential linkage of slab dehydration and fluid flow with SSEs. These results would have great implication for unraveling the genetic mechanism of SSEs on subduction zones.