InSAR observations of post-rifting deformation around the Dabbahu rift segment, Afar, Ethiopia
InSAR observations of post-rifting deformation around the Dabbahu rift segment, Afar, Ethiopia
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DOI：
10.1093/gji/ggu003
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发表时间：
2014-04
影响因子：
2.8
通讯作者：
I. Hamling;T. Wright;É. Calais;E. Lewi;Y. Fukahata
中科院分区：
文献类型：
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作者：
I. Hamling;T. Wright;É. Calais;E. Lewi;Y. Fukahata
摘要 在许多大地震和岩浆事件之后，人们观察到位移率增加。尽管比与主要事件相关的位移小一个数量级，但震后或裂谷后变形可能会在最初的地震或堤坝入侵后持续数年至数十年。由于空中裂谷事件很少发生，很少有观测来约束裂谷后变形的模型。2005年9月，一条60公里长的堤坝沿着努比亚-阿拉伯板块边界的达巴胡段（埃塞俄比亚阿法尔）侵入，标志着正在进行的裂谷事件的开始。使用卫星雷达干涉测量法和部署在裂谷周围的全球定位系统仪器的数据来监测持续的活动，以响应最初的入侵。使用多个卫星通道，我们能够分离达巴胡段周围的裂谷垂直和垂直位移场。裂谷垂直率和垂直率分别高达 180 和 240 mm yr -1 。在这里，我们表明，仅粘弹性松弛模型不足以再现观测到的变形场，并且观测到的信号的很大一部分与裂谷段内的岩浆运动有关。我们的模型表明上地幔粘度为 10 18−19 Pas，上面覆盖着 15 至 30 公里的弹性地壳。为了拟合观测结果，裂谷中心和裂谷轴东南部的岩浆房的膨胀和收缩需要分别达到∼0.13和-0.08km 3 yr -1 的速率。
SUMMARY Increased displacement rates have been observed following manylarge earthquakes and mag- matic events. Although an order of magnitude smaller than the displacements associated with the main event, the post-seismic or post-rifting deformation may continue for years to decades after the initial earthquake or dyke intrusion. Due to the rare occurrence of subaerial rifting events,thereareveryfewobservationstoconstrainmodelsofpost-riftingdeformation.In2005 September, a 60-km-long dyke was intruded along the Dabbahu segment of the Nubia-Arabia Plate boundary (Afar, Ethiopia), marking the beginning of an ongoing rifting episode. Con- tinued activity has been monitored using satellite radar interferometry and data from global positioning system instruments deployed around the rift in response to the initial intrusion. Using multiple satellite passes, we are able to separate the rift perpendicular and vertical displacement fields around the Dabbahu segment. Rift perpendicular and vertical rates of up to 180 and 240 mm yr −1 , respectively. Here, we show that models of viscoelastic relaxation alone are insufficient to reproduce the observed deformation field and that a large portion of the observed signal is related to the movement of magma within the rift segment. Our models suggest upper mantle viscosities of 10 18−19 Pas overlain by an elastic crust of between 15 and 30km. To fit the observations, inflation and deflation of magma chambers in the centre of the rift and to the south east of the rift axis is required at rates of ∼0.13 and −0.08km 3 yr −1 .