Urgent deployment of GPS in Afar (Ethiopia): determining the rheology of incipient oceanic lithosphere

当构造板块分开时，新的海洋地壳最终形成。由于岩浆沿着大洋中脊的垂直裂缝（岩脉）沿着侵入，地壳会间歇性地（对任何特定的部分来说，大约每隔几百年）生长。世界上大多数海洋地壳都在几公里深的水下，不可能直接观察堤坝侵入过程。9月14日，在东非裂谷系统北方的阿法尔（埃塞俄比亚），一个堤坝侵入事件开始在陆地上发生，那里的大陆地壳刚刚被拉伸到足以形成“海洋”地壳。一个60公里长的裂谷部分打开了9米，超过2立方公里的岩浆侵入。有许多地震和火山爆发从长，开放的裂缝在表面，覆盖了一个广泛的地区的灰烬，流离失所约25,000牧民和他们的牲畜。这是自20世纪70年代以来第一次发生在陆地上的重大堤坝入侵事件，也是第一次发生在精确的天基测量技术时代。除了希望了解任何未来活动的可能性，该事件还建立了一个简单的自然实验，将帮助我们了解地球外层的特性。从本质上讲，入侵给了地球一个突然的踢。测量它对这种反冲的反应可以告诉我们深处岩石的行为。特别是，我们感兴趣的是，我们是否可以看到这些岩石流动，以回应的压力踢，以及如何快速流动。我们计划在地面上安装全球定位系统仪器，以持续监测地壳的运动，并利用卫星雷达图像获取变形的快照。通过这些测量的结合，我们将能够了解大陆分裂和海洋板块生长的过程。

When tectonic plates move apart, new oceanic crust is eventually formed. This crust grows episodically (every few hundred years or so for any given segment) by the intrusion of magma along vertical cracks (dykes) at mid-ocean ridges. Most of the world's oceanic crust is under several kilometres of water where it is impossible to directly observe the dyke intrusion process. On the 14 September a dyke intrusion event began on land at the northern end of the East African Rift system, in Afar (Ethiopia) - where continental crust has just been stretched sufficiently for 'oceanic' crust to be formed. A 60 km long segment of the rift opened by as much as 9 m, and more than 2 cubic kilometres of magma was intruded. There were many 10s of earthquakes and eruptions from long, open fissures at the surface, blanketed a wide area in ash, displacing some 25,000 pastoralists and their livestock. This is the first major dyke intrusion event on land since the 1970s, and the first to occur in the era of precision space-based measuring techniques. As well as wishing to understand the likelihood of any future activity, the event sets up a simple natural experiment that will help us understand the properties of the earth's outer layers. In essence, the intrusion has given the earth a sudden kick. Measuring how it responds to that kick tells us about how the rocks at depth behave. In particular, we are interested in whether we can see those rocks flow in response to the stress of the kick, and how quickly they flow. We plan to install GPS instruments on the ground that will monitor the movement of the crust continuously, and to use satellite radar images to get snapshots of the deformation. From the combination of these measurements, we will be able to learn about the processes by which continents split apart and oceanic plates grow.