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Home  >  Volume 36 (no2)

Determination of Moho depth and Vp/Vs ratio in Nigeria from a Local Earthquake by Ezomo O. F and Afegbua K. U (pages 367-376)
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The depth of discontinuity between the crust and upper mantle (Moho depth) as well as ratio of the Compressional to Shear wave velocities (Vp/Vs) in Nigeria, have been determined using the Primary (P) and Secondary (S) elastic waves from the 2009 earthquake in Nigeria. The methodology involves the modeling of the earthquake recorded by the Nigerian Seismic Stations located in Ife, Kaduna and Nsukka respectively, using a Pyrocko algorithm that implements wave propagation within 1500km fringe of the epicenter to the receiver, as a function of ray parameters; adopting a Global Earth Velocity model. The results showed that the moho depths beneath Ife, Kaduna, and Nsukka stations were respectively 39km, 38km, and 28km. The computed Vp and Vs for the depth profile (100-300km) in the Southwestern Nigeria, increased from 5.83-6.42 and 3.48-6.31km/secs respectively; with Vp/Vs decreasing from 1.68 to 1.67 within the same depths. The aim of this work, therefore, is to determine the crustal structure of Nigeria (Moho depth and velocities) in order to improve on the mechanics of earthquakes location, as well as to aid future seismic hazard and micro-zonation studies for proper planning and development in the Nigeria.

Keywords: Nigerian Seismic Stations, the 2009 earthquake, crustal structure, Vp/Vs ratio