Application 4D Resistivity Method for Determining Effect of Water Content; Case Study ITERA Campus

Abstract

This is a study of the application of the time lapse resistivity method (4D resistivity) to analyze the dynamics of the movement of subsurface fluids (ground water). This study used to analyze the decline in the ground water table due to differences in the rainy and dry seasons. The 4D resistivity study was conducted at the ITERA campus in June (rainy season) and September (dry season). The resistivity method used Electrical Resistivity Tomography (ERT) with the Wenner Alpha configuration. Data acquisition uses 36 simultaneous channel with ARES Multichannel and Multielectrode resistivity meters instrument with length is 385 meters. Based on the first measurement (rainy season), it was found an unconfined aquifer layer with a moderate resistivity value (11-80 Ω.m) which was assumed to be tuffaceous sandstone at a depth of 11-35 m. Whereas in the second measurement (dry season), it was found an unconfined aquifer layer with a moderate resistivity value (11-80 Ω.m) which was assumed to be tuffaceous sandstone at a depth of 11-28 m. Based on the results of time lapse inversion processing, it is found that the change in resistivity for the two sets of data almost the same at all measurement points, except at certain points, which shows a greater percentage. This shows the change in resistivity values if measured at different times. This difference is due to the absorption of rainwater by the surface which then migrates into the inner layer.