Active Development of Continental Rifts: Wide Swath Interferometry in East Africa.

在一个不确定的世界里，我们喜欢把地面看作一个坚固的、不可移动的平台，但即使是大陆也在我们脚下慢慢漂移；陆地和海洋的格局不断变化。东非正在逐渐被板块构造的力量撕裂--最终将有一个新的海洋，但在今天，我们已经可以看到开始：3000公里长的大裂谷，其中包含一连串的火山，而且容易发生地震。但接下来会发生什么呢？已有的观点认为，当两个地块在断层上相互滑动时，地震时会发生伸展。然而，最近的卫星观测表明，岩浆是重要的。想象一下，将两块堆叠在一起的木头滑动开--摩擦力会抵抗你。现在想象一下，木片漂浮在池塘上：这是一项容易得多的任务，摩擦力更小，水流可以填补缺口。这与东非发生的情况类似--岩浆的存在改变了非洲大陆的伸展方式。科学家们正在研究一种新的范式，在这种范式中，岩浆在大陆裂谷中扮演着关键角色。在开发新的模型之前，我们需要一套清晰的观察结果来测试它们。目前只有几个案例研究--然而我们需要看到整个裂谷中岩浆和断层运动的模式：伸展是集中在断层上还是靠近火山是山谷的中心？那里有多少岩浆？岩浆以短脉冲上升，就像水滴一样，但是什么控制了这些水滴的形成呢？开始回答这些问题的最好方法是使用卫星观测--避免对偏远和危险地形进行耗时的探险。使用基于卫星的雷达，可以用一张图像覆盖数百公里的裂谷，并探测到与伸展和岩浆在地下移动有关的少量隆起或下沉。一旦确定了令人关注的特定领域，就可以使用地面工具来提供关于个别实例的更详细的意见。使用大型卫星图像的档案，我将分析跨越7年的地面运动，覆盖从埃塞俄比亚到马拉维的裂谷长度。这些观测将描述断层作用和岩浆在空间和时间上的运动模式，从而发展出一类新的大陆裂谷模型，包括岩浆的影响。除了这些科学目标外，该项目还将产生关于目前被低估的潜在危险来源的信息，我们将把结果传达给当地和全球管理机构。

We like to think of the ground as a solid, immovable platform in an uncertain world, but even the continents are slowly drifting beneath our feet; the patterns of land and sea constantly changing. East Africa is being gradually pulled apart by the forces of plate tectonics - eventually there will be a new ocean, but at the present day, we can already see the beginnings: the three thousand kilometre long Great Rift Valley containing a string of volcanoes and prone to earthquakes. But what happens next? The established view is that stretching takes place during earthquakes as two blocks slide past each other on faults. Yet recent satellite observations have shown that magma is important. Imagine sliding apart two pieces of wood stacked on top of each other - the forces of friction resist you. Now imagine the pieces of wood are floating on a pond: this is a much easier task, there is less friction and the water flows to fill the gap. This is similar to what happens in East Africa - the presence of magma alters the way in which the continent stretches. Scientists are working on a new paradigm, one in which magma plays a crucial role in continental rifts. Before new models can be developed, we need a clear set of observations against which to test them. Currently only a few case studies are available - yet we need to see the patterns of magma and fault movement throughout the rift: Is the stretching focused on the faults or near the volcanoes the centre of the valley? How much magma is there? Magma rises in short pulses, like drips, but what controls how these drips form? The best way to begin answering these questions is to use satellite observations - avoiding the need for time-consuming expeditions to remote and dangerous terrain. Using satellite-based radar, it is possible to cover hundreds of kilometres of the rift with a single image and detect small amounts of uplift or subsidence associated with stretching and magma moving underground. Once particular areas of concern have been identified, ground-based instruments can be used to provide more detailed observations on individual examples. Using the archive of large satellite images, I will analyse ground movement spanning 7 years and covering the length of the rift, from Ethiopia to Malawi. These observations will describe the pattern of faulting and magma movement in space and time, allowing the development of a new class of continental rifting models, to include the effects of magma. In addition to these scientific goals, this project will generate information on what is currently an underestimated source of potential hazard and we will communicate the results to local and global management bodies.