Geophysical Mapping of Kyamwilu Area, Machakos County, Kenya, Using Electrical Resistivity Technique

Vertical Electrical Sounding method was carried out at Kyamwilu in Machakos County. The research was carried out within an area of about 2km2 due to the rough terrain along the road reserve to map out electrical resistivity at with lower and upper coordinates spread of 031492E and 9942259N, respectively. Three H. E. P using the ABEM SAS 300B Terra-meter were identified with 12 VES sites analyzed and interpreted using the IpWin software and results were tabulated using the Surfer 10. The results revealed that the area is characterized by at least Eight geo-electrical layers, with Two surface layers of topsoil (alluvial and sandy clay) with resistivity and thickness values from 193 m-700 m, 2.57m respectively in a Profile drawn NE-SE direction, Two fractured and slightly compact layer ranging from 158 m-9249 m, 11.7m thickness for a profile drawn NW-SE, Three weathered/fractured layers (sandstones, limestones, silica clay, and Granite) ranging from 7.25 m -51921 m, at 10.8m-46.6m, a basement layer of weathered basalt rocks at resistivity greater than2043 m. From the research, resistivity values varied due to clay deposits, the porosity of rocks and subsurface faults in the area.