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.

俯冲带是发生大地震和海啸的地方，但由于地质和水文条件沿沿着边界变化，区域人类风险也各不相同。太平洋板块滑下哥斯达黎加下方的“巨型逆冲断层”内存在（可能是润滑）流体，这将被记录下来，并与地震活动的模式有关。在巨型逆冲断层之上，许多较小的断层控制着沉积楔内的变形。这项研究将提供对这一界限演变的新的理解，并将获得对危险范围的更完整的了解。下一代海洋科学家的培训将通过本科生参与数据分析进行，博士后学者将在整个研究中发挥重要作用。对哥斯达黎加边缘近海部分的结构进行分析，将记录沉积楔内部和底部的流体路径，沉积楔形成覆盖巨型逆冲断层的构造板块的趾部。将对以前由R/V Langseth收集的三维多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断层的几何形状，本研究将量化断层带内的物理特性。振幅与偏移量的结果应该辨别出巨型逆冲断层的部分是否是流体轴承。与地震活动模式的关系将解决流体在控制历史滑动沿着断层的可能作用。将对充满小断层的增生楔进行详细的结构建模，以显示覆压板块的变形如何随着时间的推移而适应。对遗留海底地震折射剖面的重新分析将提供与边缘邻近部分速度结构的比较，以便可以评估沿走向的变化。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。