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Assessments of the extension directions and their variations are critical for understanding rifting processes. This study provides an overview of the extension directions along the axes of the Main Ethiopian Rift and the Red Sea Rift (or propagator) of Afar, two of the three rifts meeting at the Afar triple junction. This overview is based on new and published field data on the opening direction of significant (width >0.2 m) Holocene extension fractures along the rift axis. The data show that the Red Sea propagator axis opens orthogonally, both in northern and central Afar, even though a significant strike-slip component is recognized at the rift margins in central Afar. The Main Ethiopian Rift axis also opens orthogonal to the trend of the rift, which varies between the different rift segments. Therefore, the axes of two of the three rifts meeting in Afar are characterized by orthogonal extension. However, given the variable orientations of the rift segments, the obtained opening directions are usually not uniform along the rift. Current plate-motion models suggest slightly different divergence directions, especially along the Main Ethiopian Rift, which shows a significant oblique component. The discrepancy between the data along the rift axis and those from plate-motion models suggests an across-rift strain partitioning. The observed orthogonal extension along the rift axis may be magma-induced, provided that a depth-dependent variation in the kinematics exists, at least below the Main Ethiopian Rift axis.

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