THE CRUSTAL STRUCTURE OF NORTHERN KENYA RIFT: RESULTS FROM MICRO EARTHQUAKES DATA.

Crustal structure beneath the northern Kenya Rift valley is investigated using micro seismic data from eight Seismic stations. The events are located using seiscomp3 and the program hypoDD is used for relocation of events in order to correlate the geological structures to event location. The earth velocity model is generated using VELEST software. The Vp/Vs is computed using a UNIX shell sc ript that utilizes the 157 events located. There after the Poisson��s ratio is computed from the Vp/Vs. The results obtained here reveal two major crustal layers namely the first layer with a thickness of 10 km and increasing P wave velocity of 2.63 to 5.94 km/s and the second layer with a thickness of 12 km and an increasing P wave velocity from 5.94 to 7.08 km/s whose lower interface coincides with a sharp Moho discontinuity. The average value for the Poisson��s ratio is 0.29. The average S wave velocities for the crust a is 3.75 km/s. Paka prospect is highly fractured and majority of events picked are located around the areas with major and minor fractures and faults. It can be concluded that the activity observed in Paka Korosi is related to local tectonic activity that is prominent in the area and the other events can be related to tectonic movements along the rift system.

Key words: Crustal structure, Double Diffe rence (Hypo DD), Velocity model