Application of Vertical Electrical Sounding and Horizontal Profiling Methods to Decipher the Existing Subsurface Stratification in River Segen Dam Site, Tigray, Northern Ethiopia

Abstract

The study area Segen river dam site is situated in the southeastern zone of Tigray National Regional State in between Hintalo Wajirat and Enderta weredas. It is geographically located at 37P between 541400 to 542600 UTME Latitude and 1481600 to 1482600 UTMN Longitude about 35 km southwestern part of Mekelle, the capital of Tigray National Regional State. The study was conducted having an objective of the geophysical assessment to provide important subsurface geophysical information useful in evaluating the subsurface geological formations, geological structures,  cavities and others for the dam site under investigation. Ten Vertical Electical Sounding (VES) points along the two profile lines and a total of two Horizontal Profiling (EP) with a Wenner electrode array were collected. VES datas were entered to the computer and curves were plotted using IPI2win interpretation software. EP are entered into the computer and processed using Microsoft Office Excel and Golden Software Surfer V. 8. The VES results have shown that weak zones at VES 2, VES 3 and VES 4 along profile 1 and at VES 2, VES 3 and VES 5 along profile 2 where the depth goes no more 20 m deep in both profiles’ pseudo cross section except at VES 4 profile which extends up to 30 m deep. Similarly, the electrical resistivity profiling results also have shown that the weak zones extend no more than 20 m of depth. Hence, the result revealed that the investigation requires further core drilling investigations.

Key words: vertical electrical sounding, horizontal profiling, subsurface, goephysical, dam, Segen, Tigray, Ethiopia