The crustal and the upper mantle structure of southwestern Nigeria from inversion of teleseismic surface waves

No detailed information has been provided on the shear-wave velocity structure of the crust and the upper mantle of Nigeria till-date. In this study, the depth distribution of seismic wave velocities over southwestern Nigeria was determined using teleseismic surface waves of different azimuths recorded by our 3-component broadband station between November 2009 and 2011. The group velocities of Rayleigh and Love waves with surface wave magnitude �√ 6.0 in the period range of 16 – 100 s were inverted for plane-layered earth shear-velocity structure. The shear-wave velocity of the crust increases gradually from about 3.12 to 4.29 km/s. The Moho was found at the depth of 40 km. The upper mantle shear-velocity increases from about 4.37 to 4.5 km/s between the depths of 40 and 73 km and a low velocity layer between the depths of 73 km and 238 km with shear-wave velocity of 4.01 – 4.47 km/s. An average values for the crust and the upper mantle velocities have been assumed over southwestern Nigeria from seismic data of a single seismic station within this region, however, further studies using data from many stations when available in this area will help to improve on the result of this study.