A Community Velocity Field for East Africa

The break-up of Africa along the East African Rift System has long served as the type example of how stable continents fall apart in tectonic cycles. As a result, many geophysical and geologic studies have measured and analyzed different sections of the very long rift system in detail, including studies using GPS geodesy to measure the speed, direction, and distribution in space of the ongoing separation of most of Africa (Nubia) from its eastern part (Somalia). However, few, if any, of these previous studies took a comprehensive view over the whole rift and continent, in order to explore how different sections of the rift link together, interact with one another, or influence neighboring parts of the continent outside of the rift valleys. Such a comprehensive view is necessary to better understand the whole continent and, indeed, how other continents split apart in the past or will in the future. The broad process of rifting forms the basis of plate tectonic theory, and also influences the distribution of earthquakes, volcanoes, geothermal resources, mineral resources, and topography in both time and space.

This experiment addresses two pieces of the task of building such a continent-scale view of rifting. First, it includes compiling all known geodetic observations in Africa and surrounding regions from 22 different research groups representing 10 countries. These data will then be combined into a single large-scale velocity field, thus minimizing any uncertainties in relative velocities (and strain rates) arising from variations in reference frame definitions, processing strategies, or network geometries. Second, it includes re-measurements of high-value sites with limited or poor past measurement histories, including a campaign network spanning the Turkana Depression of the Kenya-Ethiopia borderlands, where two parallel active rift structures in Kenya relay to a single rift in Ethiopia. Both of these efforts are directed at providing the highest possible quality present-day tectonic velocity field for the whole African Rift System at the continent scale, as a basic research product and as an open-access kinematic framework for many other diverse research efforts directed at the African system and rifting in general.