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|Title:||Seismicity and lithospheric structure of northern Kenya.|
|Authors:||Pointing, Alan James.|
|Presented at:||University of Leicester|
|Abstract:||Local, regional and teleseismic earthquakes recorded at seismic stations in northern Kenya have been analysed to determine the seismicity in this region and the crustal and upper mantle structure beneath an array on the north-eastern flank of the Kenya dome. A total of 389 microearthquakes, occurring during the period 17th Jan. to 26th Aug., 1981, have been located using a simple half space velocity model. The seismic activity is mainly confined to the Kenya rift and a zone approximately 150km to the east of the main rift. The northward extent of the activity suggests that the active section of the rift continues beneath Lake Turkana. Apparent velocities of local and regional earthquakes recorded at the Ngurunit array have been interpreted in terms of crustal velocity structure. A two layered crustal velocity model has been derived. The velocity of the upper crustal layer is considered to increase linearly with depth, according to the function V = 5.8 + 0.0245z. The velocity of the lower crustal layer is 6.5 0.2 km/s and the intermediate crustal boundary is placed at 24km. The variation of apparent velocity with azimuth of Moho arrivals suggests an eastwardly dipping Moho of 7 beneath the array. The depth of the Moho directly beneath the array is derived to be 46km and the velocity of sub-Moho material is 8.3 0.2 km/s. Delay times and slowness measurements of teleseismic P wave arrivals indicate the presence of anomalously low P wave velocity material in the upper mantle. Three-dimensional ray tracing modeling suggests a thickening of the anomalous body to the north and east of the array, such that the top surface of the body reaches to within 60-80km of the ground surface. The thickening may be associated with rift structures beneath Lake Turkana and Quaternary volcanic activity observed on the eastern flank of the Kenya dome.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, Dept. of Geology|
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