Collaborative Research: Exploring Extensional Tectonics Beyond the Ethiopian Rift

大陆裂谷系统的研究通常假设岩石圈形变与裂谷的表面表现具有相似的规模，并且在空间上与之一致。然而，努比亚和索马里之间正在进行的大陆伸展似乎局限于一个狭窄的裂谷带(埃塞俄比亚的主要裂谷)，仅位于最上面的薄薄的弹性地壳盖层中。在下地壳和地幔岩石圈的更深处，非常弱的物质似乎通过在较低应变率下在长距离尺度上进行粘性拉伸来适应伸展，导致高度依赖深度的伸展。这种可能性很重要，因为它挑战了对大陆裂谷作用的现有理解，并为研究非均质流变学对大陆力学的影响提供了机会。虽然许多人研究了埃塞俄比亚的主要裂谷，但以前的努力没有一项远远超出裂谷地带，以提供该地区的概貌。因此，没有现有数据足以测试埃塞俄比亚高地或索马里地台的分布形变。该项目将大口径GPS网和大口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要裂谷周围岩石圈内的横向和垂直形变模式。板块构造理论将大陆破裂作为其基本原理之一。在过去，大陆块既有合并又有破裂，但目前尚不清楚大陆分裂是如何在空间和时间上进行的，除了普遍推断这种分裂在非均质大陆材料中肯定是非常不同的。东非地区是大陆破裂的最好的持续例子，但大多数人在大裂谷中对其进行了研究，忽略了裂谷以外的任何重要过程。这项实验对大陆解体有更广泛的看法，不仅研究地表裂谷，还研究远远超出裂谷的变形。这些结果对全面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。这些结果还将有助于绘制新的地热资源、地震和火山灾害以及非洲高山和高原的起伏。

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.