Y1 (2018-2021): Crust and mantle structure and the expression of extension in the Turkana Depression of Kenya and Ethiopia

• Tulane University (TU), United States of America

We propose to make a set of targeted seismic and geodetic in the Turkana Depression and its immediate surroundings, ultimately to differentiate between three competing models for the topographic low between two broad zones of uplift: 1) Two distinct mantle plumes with the Turkana Depression a ‘passive’ structure lying between the two (e.g., George et al., 1998; MacDonald et al., 2001; Furman et al., 2006; Pik et al., 2006; Lin et al., 2005; Chang et al., 2011); 2) One superplume province with a pre-existing mantle thin zone (Mesozoic and/or Paleogene rifts) that channel hot asthenosphere susceptible to melting, and preferentially reactivate older sedimentary basins (e.g., Ebinger and Sleep, 1998; Halldorsson et al., 2014). Specifically, we will use the geodetic and seismic observations in combination with forward multi-physics simulations to differentiate between end-member hypotheses for cratonic rifting: A) GPE from isostatic and dynamic topography dominantly influences surface deformation; B) Lateral variations in material properties dominantly influence surface deformation. We plan a two-year, 22-station broadband seismic and three-year, 6-station continuous GPS deployment, with two-sets of observations at the 14 existing eGPS sites to distinguish between the two end-member models for lithospheric strain presented above, and to specific questions below (Fig. Seismic Plan). The study area is logistically challenging, but oil production in the most remote areas and ties to the Turkana Basin Institute (see letter), as well as Bendick’s current experience afford unprecedented opportunities. Ebinger has worked for 2 decades in both Ethiopia and Kenya, and she is collaborating with Kianji in southern Kenya.

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