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

对哥斯达黎加边缘 3D 地震体进行定量分析，揭示俯冲带结构、构造和孕震带的发育

• 批准号: 1435386
• 负责人: Nathan Bangs
• 金额: $ 37.24万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-10-01 至 2017-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1435386&HistoricalAwards=false
• 关键词: Quantitative; analysis; Costa; Rica; margin

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.

俯冲带是发生主要地震和海啸产生的地方，但由于地质和水文条件在给定的边缘变化，因此区域人类风险有所不同。在“巨型断层”中，（可能润滑）流体的存在将记录在哥斯达黎加以下，并与地震性模式有关。在巨型断层上方，许多较小的断层控制沉积楔内的变形。这项研究将提供对该利润率演变的新理解，并将更完整地了解危害范围。下一代海洋科学家的培训将通过参与本科生参与数据分析的培训，而博士后学者将在整个研究中发挥重要作用。分析哥斯达黎加边缘的近海部分的结构将记录在沉积楔的内部和底部的流体途径，形成了构成构造板块的脚趾，从而覆盖了构造板块的脚趾。将对先前由R/V Langseth收集的3-D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质的几何形状，这项研究将量化断层区域内的物理特性。振幅与偏移结果应辨别大型断层的部分是否是流体轴承。与地震性模式的关系将解决流体在控制过故障的历史滑移中的可能作用。将进行带有小断层的增生楔的详细结构建模，以显示如何随着时间的推移容纳压倒板的变形。遗留海洋底部地震折射率的重新分析将与边缘相邻部分的速度结构进行比较，以便可以评估沿撞状可变性。这些发现将为解释过去和未来的科学海洋钻井结果提供关键背景。