Collaborative Research: Exploring Extensional Tectonics Beyond the Ethiopian Rift

合作研究：探索埃塞俄比亚裂谷之外的伸展构造

• 批准号: 1118931
• 负责人: Lucy Flesch
• 金额: $ 27.59万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1118931&HistoricalAwards=false
• 关键词: Collaborative; Research; Exploring; Extensional; Tectonics

Research in continental rift systems commonly assumes that lithospheric deformation has a similar scale to and is spatially coincident with the surface expression of rifting. However, ongoing continental extension between Nubia and Somalia appears localized to a narrow rift zone (the Main Ethiopian Rift) only in the thin elastic uppermost crustal lid. At greater depths in both the lower crust and mantle lithosphere, very weak materials appear to accommodate extension by viscous stretching over long length scales at lower strain rates, resulting in highly depth-dependent stretching. This possibility is important because it challenges existing understanding of continental rifting and provides an opportunity to investigate the implications of heterogeneous rheology for continental mechanics. Although the Main Ethiopian Rift has been studied with many, none of the previous efforts have extended far beyond the rift zone to provide a synoptic view of the region. Therefore, no existing data suffice to test for distributed deformation in the Ethiopian Highlands or the Somali Platform. This project combines a large-aperture GPS network and a large-aperture broadband seismometer array with numerical modeling to characterize the lateral and vertical deformation patterns within the lithosphere surrounding the Main Ethiopian Rift.The theory of plate tectonics includes continental breakup as one of its fundamental principles. In the past, continental masses have both coalesced and fractured but it is unclear how continental breakup progresses over space and time, aside from general inferences that this breakup must be very variable in heterogeneous continental materials. The East African region is the best ongoing example of a fracturing continent, but it has mostly been studied in the great rift valleys, omitting any important processes extending beyond the rift. This experiment takes a broader view of continental breakup, studying not only surface rifting, but also deformation far beyond the rift. The results have potential scientific implications for the general understanding of plate tectonics processes and of the fundamental properties of the continents. The results will also help map new geothermal energy resources, earthquake and volcano hazards, and the rise and fall of high mountains and plateaus in Africa.

大陆裂谷系统的研究通常假定岩石圈变形与裂谷作用的地表表现具有相似的规模和空间一致性。然而，努比亚和索马里之间正在进行的大陆伸展似乎只局限于一个狭窄的裂谷带（埃塞俄比亚主裂谷），在薄的弹性最高地壳盖。在下地壳和地幔岩石圈的更深处，非常弱的物质似乎可以在较低的应变率下通过长尺度的粘性拉伸来适应拉伸，从而导致高度依赖于深度的拉伸。这种可能性是重要的，因为它挑战了现有的大陆裂谷的理解，并提供了一个机会，研究大陆力学的非均质流变学的影响。虽然埃塞俄比亚主裂谷已经研究了许多，但以前的努力都没有延伸到裂谷带以外，以提供该地区的天气视图。因此，没有现有的数据足以测试在埃塞俄比亚高地或索马里平台的分布变形。该项目将大孔径全球定位系统网络和大孔径宽带地震仪阵列与数值模拟相结合，以确定埃塞俄比亚主裂谷周围岩石圈内横向和垂直变形模式的特征。在过去，大陆块体既有合并也有断裂，但目前还不清楚大陆断裂在空间和时间上的进展，除了一般的推断，这种断裂在异质大陆材料中必须是非常可变的。东非地区是断裂大陆最好的例子，但它主要是在大裂谷中进行研究，忽略了任何延伸到裂谷之外的重要过程。这个实验对大陆分裂有更广泛的看法，不仅研究表面裂谷，而且研究裂谷以外的变形。这些结果对一般了解板块构造过程和大陆的基本性质具有潜在的科学意义。研究结果还将有助于绘制新的地热能资源、地震和火山危险以及非洲高山和高原的升降图。