Investigation into the weathering layer using up-hole method of seismic refraction.

Project Abstract

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

Project Overview