Quantitative analysis of the Costa Rica margin 3D seismic volume to reveal subduction zone structure, tectonics, and the development of the seismogenic zone

俯冲带是大地震和海啸发生的地方，但由于地质和水文条件沿着给定的边缘变化，区域人类风险有所不同。太平洋板块在哥斯达黎加下方滑下的“大逆冲断层”内存在（可能是润滑的）流体将被记录下来，并与地震活动模式相关。在大逆冲断层之上，许多较小的断层控制着沉积楔内部的变形。这项研究将为这一边缘的演变提供新的认识，并将获得一个更完整的危险范围的图片。下一代海洋科学家的培训将通过本科生参与数据分析来进行，博士后学者将在整个研究过程中发挥重要作用。对哥斯达黎加边缘近海部分结构的分析将记录沉积楔内部和底部的流体路径，沉积楔形成了覆盖在大逆冲断层上的构造板块的脚趾。将对先前由R/V Langseth收集的三维多通道地震反射数据集进行高级分析。先前的研究确定了巨型逆冲构造的几何形状，而本次研究将量化断裂带内的物理性质。振幅与偏移量的对比结果可以辨别出大逆冲断层的某些部分是否含流体。与地震活动模式的关系将解决流体在控制断层历史滑动中的可能作用。将对布满小断层的增生楔进行详细的结构建模，以显示上覆板块的变形是如何随着时间的推移而适应的。重新分析遗留的海底地震折射剖面将提供与边缘邻近部分的速度结构的比较，从而可以评估沿走向的变异性。这些发现将为解释过去和未来可能的科学海洋钻探结果提供关键背景。

Subduction zones are where major earthquakes and tsunami generation occur but the regional human risk varies since geologic and hydrologic conditions vary along a given margin. The presence of (possibly lubricating) fluid within the 'megathrust fault' where the Pacific plate slides down beneath Costa Rica will be documented and related to the pattern of seismicity. Above the megathrust fault, many smaller faults control deformation within the sedimentary wedge. This study will provide new understanding of this margin's evolution and a more complete picture of the range of hazards will be obtained. Training of next generation marine scientists will take place via involvement of undergraduate students in the data analysis and a postdoctoral scholar will play a significant role throughout the study. Analysis of the structure of an offshore portion of the Costa Rica margin will document fluid pathways within and at the base of the sedimentary wedge that forms the toe of the tectonic plate that overrides the megathrust fault. Advanced analysis of the 3-D multi-channel seismic reflection dataset previously collected by the R/V Langseth will be conducted. Prior study determined the geometry of the megathrust and this study will quantify physical properties within the fault zone. Amplitude versus offset results should discern whether portions of the megathrust fault are fluid bearing. The relation with seismicity patterns will address the possible role of fluids in controlling historical slip along the fault. Detailed structural modeling of the accretionary wedge, which is riddled with small faults, will be conducted to show how deformation of the overriding plate is accommodated over time. Re-analysis of a legacy ocean bottom seismic refraction profile will provide comparison to velocity structure in a neighboring part of the margin so that along-strike variability can be assessed. The findings will provide key context for interpretations of past and possible future scientific ocean drilling results.