Perpustakaan Digital ITB

Direct interpretation is a quick method to interprct geophysical data without involving sophisticated inversion technique. Zohdy (1989) interpreted directly Schlumberger sounding data into depths and resistivities from shifted elecrrode spacings and adjusted apparent resistir ities. respectively. ln this paper, we adopted this method and expa.nded it by deriving its depths and resistivities from changes in the apparent resistiviry due to changes in electrode spacing and changes in layer resistivities, Three main procedures were carried out. First, we calculated the Schlumberger sounding curve using linear filtering method. Second, we derived the sounding curve against the changes in electrode spacings as well as changes in depths. Third, we determined the thickness and resistivity of each layer using changes in apparent resistivities.We calried out examination using 10 different layered earth models, all in the absence and presence of noise. Layered eafih models werc selected using data from literature that show geologically reasonable layering models. This result shows that the modified Zohdy method can improve the interpreted resistivity distribution even in the presence of noise. This technique allows us to use the suppression and expansion of layer. both in fbrward modeling and in direct interpretation.