Present‐day kinematics of the East African Rift
Present‐day kinematics of the East African Rift
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DOI：
10.1002/2013jb010901
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发表时间：
2014-04
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影响因子：
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通讯作者：
E. Saria;Eric Calais;D. S. Stamps;D. Delvaux;C. Hartnady
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文献类型：
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作者：
E. Saria;Eric Calais;D. S. Stamps;D. Delvaux;C. Hartnady
东非大裂谷（EAR）是研究驱动大陆裂谷作用和分裂过程的典型地区。由于非洲近期空间大地测量数据的增加，努比亚板块和索马里板块之间这条约5000千米长的离散板块边界的当前运动学特征开始被揭示出来。在此，我们使用一个新的数据集，它结合了努比亚板块、索马里板块和南极板块上的间歇性全球定位系统（GPS）测量以及连续测量数据，同时结合西南印度洋中脊沿线的地震滑动矢量方向和地质指标，来更新东非大裂谷现今的运动学特征。我们利用地质和地震数据来确定主要的裂谷断层，并在考虑锁定活动断层上弹性应变积累的情况下求解刚性块体的旋转。我们发现，数据与一个包含三个位于东非大裂谷内、介于努比亚板块和索马里板块之间（维多利亚板块、鲁伍马板块和伦德勒板块）的微板块的模型最为吻合，这与先前的研究结果一致，但扩张速率较慢。我们发现地震滑动矢量提供的信息与GPS速度一致，并有助于显著降低板块角速度估计的不确定性。我们还发现，西南印度洋中脊316万年的平均扩张速率（MORVEL）系统性地比仅根据GPS数据预测的要快。这可能表明西南印度洋中脊的向外位移大于MORVEL板块运动模型中使用的默认值。
The East African Rift (EAR) is a type locale for investigating the processes that drive continental rifting and breakup. The current kinematics of this ~5000 km long divergent plate boundary between the Nubia and Somalia plates is starting to be unraveled thanks to a recent augmentation of space geodetic data in Africa. Here we use a new data set combining episodic GPS measurements with continuous measurements on the Nubian, Somalian, and Antarctic plates, together with earthquake slip vector directions and geologic indicators along the Southwest Indian Ridge to update the present‐day kinematics of the EAR. We use geological and seismological data to determine the main rift faults and solve for rigid block rotations while accounting for elastic strain accumulation on locked active faults. We find that the data are best fit with a model that includes three microplates embedded within the EAR, between Nubia and Somalia (Victoria, Rovuma, and Lwandle), consistent with previous findings but with slower extension rates. We find that earthquake slip vectors provide information that is consistent with the GPS velocities and helps to significantly reduce uncertainties of plate angular velocity estimates. We also find that 3.16 Myr MORVEL average spreading rates along the Southwest Indian Ridge are systematically faster than prediction from GPS data alone. This likely indicates that outward displacement along the SWIR is larger than the default value used in the MORVEL plate motion model.