This paper is aimed at using up-hole method of seismic refraction survey to investigate the thickness of
the weathering layer as well as the velocity of seismic waves through the layer. The first events to arrive
at the geophones on a refraction profile had travelled by refraction along the top of the high speed zone
just below the weathering layer. Using the time- offset curves of the first arrivals for shots from different
charge depths; the thickness of the weathering layer was calculated by conventional seismic refraction
methods. Such a survey was carried out using a TD500 top drive drilling machine mounted on a 6 × 6 m
truck. The depth of the weathering layer as well as the velocities of seismic waves in the weathering
layer and the refractor, were calculated from critically refracted arrivals using flat layer models. Using
the time-intercept method for interpretation, the thickness of the low velocity weathering layer in the
area varied from 15 to 20 m with a regional average of 18.15 m. The p-wave velocity in the uppermost
layer varied from 1385 to 800 m/s with an average value of 1092 m/s. This is a direct experimental proof
of low velocity zone confirming the weathered nature of the area.
Henry, O (2018). Investigation into the weathering layer using up-hole method of seismic refraction.. Afribary.com: Retrieved February 18, 2019, from https://afribary.com/works/investigation-into-the-weathering-layer-using-up-hole-method-of-seismic-refraction
Ohaegbuchu, Henry. "Investigation into the weathering layer using up-hole method of seismic refraction." Afribary.com. Afribary.com, 28 Nov. 2018, https://afribary.com/works/investigation-into-the-weathering-layer-using-up-hole-method-of-seismic-refraction . Accessed 18 Feb. 2019.
Ohaegbuchu, Henry. "Investigation into the weathering layer using up-hole method of seismic refraction.". Afribary.com, Afribary.com, 28 Nov. 2018. Web. 18 Feb. 2019. < https://afribary.com/works/investigation-into-the-weathering-layer-using-up-hole-method-of-seismic-refraction >.
Ohaegbuchu, Henry. "Investigation into the weathering layer using up-hole method of seismic refraction." Afribary.com (2018). Accessed February 18, 2019. https://afribary.com/works/investigation-into-the-weathering-layer-using-up-hole-method-of-seismic-refraction