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: 1119209
• 负责人: Rebecca Bendick
• 金额: $ 30.14万
• 依托单位: University of Montana
• 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 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1119209&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设岩石圈变形与裂谷的表面表现具有相似的规模并且在空间上一致。然而，努比亚和索马里之间正在进行的大陆扩张似乎仅限于薄薄的弹性最上地壳盖中的狭窄裂谷带（埃塞俄比亚主裂谷）。在下地壳和地幔岩石圈的更深处，非常弱的材料似乎可以通过在较低应变率下在长长度尺度上进行粘性拉伸来适应延伸，从而导致高度依赖于深度的拉伸。这种可能性很重要，因为它挑战了对大陆裂谷的现有理解，并提供了研究非均质流变学对大陆力学影响的机会。尽管对埃塞俄比亚主要裂谷进行了许多研究，但之前的努力都没有远远超出裂谷区域以提供该地区的概况。因此，现有数据不足以测试埃塞俄比亚高地或索马里台地的分布式变形。该项目将大孔径 GPS 网络和大孔径宽带地震仪阵列与数值模拟相结合，以表征埃塞俄比亚主裂谷周围岩石圈内的横向和垂直变形模式。板块构造理论将大陆裂解作为其基本原理之一。在过去，大陆块既合并又分裂，但目前还不清楚大陆分裂是如何在空间和时间上进展的，除了一般的推论，即这种分裂在异质大陆材料中一定是非常可变的。东非地区是大陆断裂的最好的例子，但它主要是在大裂谷中进行研究，忽略了延伸到裂谷之外的任何重要过程。该实验对大陆分裂采取了更广泛的视角，不仅研究了地表裂谷，还研究了远远超出裂谷的变形。这些结果对于板块构造过程和大陆基本属性的一般理解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源、地震和火山灾害以及非洲高山和高原的起伏。