Evidence for a Nascent Rift in South Sudan: Westward Extension of the East African Rift System?
Abstract
Joint inversion of seismic and gravity data of eastern Africa reveals a low seismic wave velocity arm stretching from the southern Main Ethiopian rift westward in an east-west direction that has not been noticed in earlier work. The zone of low velocities is located in the upper mantle and is not overlain by a known structural rift expression. We analyzed the local pattern of seismicity and the stresses in the African plate to interpret this low velocity arm. The zone of low velocities is located within the Central African Fold Belt, which dissects the northern and southern portions of the African continent. It is seismically active with small to intermediate sized earthquakes occurring in the crust. Seven earthquake solutions indicate (oblique) normal faulting and low-angle normal faulting with a NS to NNW-SSE opening direction, as well as strike-slip faulting. This pattern of deformation is typically associated with rifting. The present day stress field in northeastern Africa reveals a tensional state of stress at the location of the low velocity arm with an opening direction that corresponds to the earthquake data. We propose that the South Sudan low velocity zone and seismic center are part of an undeveloped, nascent rift arm. The arm stretches from the East African Rift system westward.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.T11F..07M
- Keywords:
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- 1219 GEODESY AND GRAVITY Gravity anomalies and Earth structure;
- 7270 SEISMOLOGY Tomography;
- 8109 TECTONOPHYSICS Continental tectonics: extensional;
- 8164 TECTONOPHYSICS Stresses: crust and lithosphere