马尼拉海沟俯冲带热结构与俯冲断层孕震机制研究

The study on thermal structure of subduction zone is of great importance in understanding of megathrust strength and seismogenic potential. In this study, we choose Manila Trench subduction zone (also referred to as Manila subduction zone) as study area to investigate the thermal structure, then the vertical range of subduction zone seismic activities and the strength of megathrust based on the thermal model constructed by the newly geological and geophysical data. The method used is finite element numerical modeling with the improved algorithm of frictional and shearing heat. The modeling results, combined with the relationship between the strength of megathrust and the probability of generating big earthquake for the globel classic subduction zones, are used to reveal the megathrust seismogenic potential of the Manila Trench subduction zone, which could offer a new perspective in assessing earthquake and tsunami hazards.

俯冲带热结构的研究对分析俯冲断层强度和地震潜在性具有重要的科学意义。本项目以马尼拉海沟俯冲带（也称马尼拉俯冲带）为研究区，利用最新的地质与地球物理观测资料，构建俯冲带热模型，采用改进的摩擦和剪切热算法进行有限元数值模拟，计算俯冲带热结构，推断俯冲带地震活动的深度范围和俯冲断层的强度。在此基础上，结合全球其它典型俯冲带俯冲断层的强度与大地震发生几率的关系，揭示马尼拉海沟俯冲带俯冲断层发生大地震的潜在性，为本区地震和海啸等重大自然灾害的评估提供新的科学依据。

马尼拉海沟俯冲带位于南海东缘，研究此区域的热结构，进而分析俯冲断层的动力学性质，对本区地震和海啸等重大自然灾害的评估具有重要的指导意义。本项目以改进的摩擦生热计算方法，获得了马尼拉海沟俯冲带更为精确的热结构。以地表实测热流为约束，推断马尼拉海沟俯冲带断层强度较高。在此基础上，计算了全球其它典型俯冲带的断层强度，发现光滑海底俯冲造成弱的断层并易引发大地震。基于马尼拉海沟俯冲断层的高强度和粗糙的俯冲海底，推断此区域发生大地震的几率较小。另外，借助以上研究成果，分析了俯冲断层随深度变化的流变学特征，发现俯冲带地震带与其下方的慢地震带在流变学上是分离的，慢地震的发生是受地幔楔角附近特殊的岩石学条件控制。这一新的流变学模型也解释了全球多种构造背景下的慢地震现象。以上研究为揭示马尼拉海沟俯冲带发生大地震的潜在性提供了新的科学依据，同时也为研究俯冲断层特征与地震活动的关系提供全新的思路。