Two-dimensional electrical resistivity tomography (2-D ERT) is one of the most common geophysical tools employed to satisfy the ever-growing need for obtaining subsurface information. Most of the conventional electrode arrays used for 2-D ERT survey are built with the theoretical assumption that the survey lines are straight to guarantee four collinear electrodes at every point of measurement. However, due to surface constraint associated with most survey areas, it is rarely possible to conduct a two-dimensional resistivity survey on a straight line. Therefore, 2-D ERT survey conducted on a surface constraint field requires shifting one or more electrodes off the survey line, which contrasts with the underlying assumption. Consequently, the result might be prone to false anomalies. Thus, this study aimed to device a new approach that could mitigate the false anomalies posed by non-collinearity of electrodes in 2-D ERT result. In view of this, ABEM Terrameter SAS4000 using Wenner array configuration was adopted for the survey. The data was acquired with all electrodes inline and one or more electrodes offline at stepwise distances, respectively. Based on the result obtained, the new approach mitigates the offline electrodes effect, as the inverse resistivity tomograms resolves the geometries of the true model reasonably well. More so, it has high R-value >90% which is an indication of proximity to the true model. Hence, it is concluded that the new approach is effective in mitigating offline electrode effect on a 2-D ERT result.

• Abdullah, F. M., Loke, M. H., Nawawi, M., & Abdullah, K. (2018). Assessing the reliability and performance of optimized and conventional resistivity arrays for shallow subsurface investigations. Journal of Applied Geophysics, 155, 237-245. https://doi.org/10.1016/j.jappgeo.2018.06.018

• Abdulrahman, A., Nawawi, M., Saad, R., Abu-Rizaiza, A. S., Yusoff, M. S., Khalil, A. E., & Ishola, K. S. (2016). Characterization of active and closed landfill sites using 2D resistivity/IP imaging: Case studies in Penang, Malaysia. Environmental Earth Sciences, 75(4), Article 347. https://doi.org/10.1007/s12665-015-5003-5

• Abidin, M. H. Z., Madun, A., Tajudin, S. A. A., & Ishak, M. F. (2017). Forensic assessment on near surface landslide using electrical resistivity imaging (ERI) at Kenyir Lake area in Terengganu, Malaysia. Procedia Engineering, 171, 434-444. https://doi.org/10.1016/j.proeng.2017.01.354

• Abudeif, A. M., Mohammed, M. A., Fat-Helbary, R. E., El-Khashab, H. M., & Masoud, M. M. (2020). Integration of 2D geoelectrical resistivity imaging and boreholes as rapid tools for geotechnical characterization of construction sites: A case study of New Akhmim city, Sohag, Egypt. Journal of African Earth Sciences, 163, Article 103734. https://doi.org/10.1016/j.jafrearsci.2019.103734

• Ahmad, F., Yahaya, A. S., Farooqi, M. A., & Tebal, N. (2006). Characterization and geotechnical properties of penang residual soils with emphasis on landslides. American Journal of Environmental Sciences, 2(4), 121-128.

• Ali, M. M., Ahmad, F., Yahaya, A. S., & Farooqi, M. A. (2011). Characterization and hazard study of two areas of Penang Island, Malaysia. Human and Ecological Risk Assessment: An International Journal, 17(4), 915-922. https://doi.org/10.1080/10807039.2011.588156

• Anastasopoulos, I. (2013). Building damage during nearby construction: Forensic analysis. Engineering Failure Analysis, 34, 252-267. https://doi.org/10.1016/j.engfailanal.2013.08.003

• Cosenza, P., Marmet, E., Rejiba, F., Cui, Y. J., Tabbagh, A., & Charlery, Y. (2006). Correlations between geotechnical and electrical data: A case study at Garchy in France. Journal of Applied Geophysics, 60(3-4), 165-178. https://doi.org/10.1016/j.jappgeo.2006.02.003

• Cubbage, B., Noonan, G. E., & Rucker, D. F. (2017). A modified Wenner array for efficient use of eight-channel resistivity meters. Pure and Applied Geophysics, 174(7), 2705-2718. https://doi.org/10.1007/s00024-017-1535-9

• Dahlin, T., & Zhou, B. (2004). A numerical comparison of 2D resistivity imaging with 10 electrode arrays. Geophysical Prospecting, 52(5), 379-398. https://doi.org/10.1111/j.1365-2478.2004.00423.x

• Fragaszy, R. J., Santamarina, J. C., Amekudzi, A., Assimaki, D., Bachus, R., Burns, S. E., Cha, M., Cho, G. C., Cortes, D. D., Dai, S., Espinoza, D. N., Garrow, L., Huang, H., Jang, J., Jung, J. W., Kim, S., Kurtis, K., Lee, C., Pasten, C., … & Tsouris, C. (2011). Sustainable development and energy geotechnology - Potential roles for geotechnical engineering. KSCE Journal of Civil Engineering, 15(4), 611-621. https://doi.org/10.1007/s12205-011-0102-7

• Godio, A., Strobbia, C., & De Bacco, G. (2006). Geophysical characterisation of a rockslide in an alpine region. Engineering Geology, 83(1-3), 273-286. https://doi.org/10.1016/j.enggeo.2005.06.034

• Griffiths, D. H., & Barker, R. D. (1993). Two-dimensional resistivity imaging and modelling in areas of complex geology. Journal of Applied Geophysics, 29(3-4), 211-226. https://doi.org/10.1016/0926-9851(93)90005-J

• Ingeman-Nielsen, T., Tomaškovičová, S., & Dahlin, T. (2016). Effect of electrode shape on grounding resistances - Part 1: The focus-one protocol. Geophysics, 81(1), WA159-WA167. https://doi.org/10.1190/GEO2015-0484.1

• Loke, M. H. (2018). Tutorial: 2-D and 3-D electrical imaging surveys. Geotomosoft.

• Loke, M. H., Acworth, I., & Dahlin, T. (2003). A comparison of smooth and blocky inversion methods in 2D electrical imaging surveys. Exploration Geophysics, 34(3), 182-187. https://doi.org/10.1071/EG03182

• Loke, M. H., & Barker, R. D. (1996). Rapid least-squares inversion of apparent resistivity pseudosections by a quasi-Newton method1. Geophysical Prospecting, 44(1), 131-152. https://doi.org/10.1111/j.1365-2478.1996.tb00142.x

• Loke, M. H., Chambers, J. E., Rucker, D. F., Kuras, O., & Wilkinson, P. B. (2013). Recent developments in the direct-current geoelectrical imaging method. Journal of Applied Geophysics, 95, 135-156. https://doi.org/10.1016/j.jappgeo.2013.02.017

• Martínez-Moreno, F. J., Pedrera, A., Ruano, P., Galindo-Zaldívar, J., Martos-Rosillo, S., González-Castillo, L., Sánchez-Úbeda, J. P., & Marín-Lechado, C. (2013). Combined microgravity, electrical resistivity tomography and induced polarization to detect deeply buried caves: Algaidilla cave (Southern Spain). Engineering Geology, 162, 67-78. https://doi.org/10.1016/j.enggeo.2013.05.008

• Muhammad, S. B., & Saad, R. (2018). Linear regression models for estimating true subsurface resistivity from apparent resistivity data. Journal of Earth System Science, 127(5), Article 64. https://doi.org/10.1007/s12040-018-0970-z

• Pando, L., Pulgar, J. A., & Gutiérrez-Claverol, M. (2013). A case of man-induced ground subsidence and building settlement related to karstified gypsum (Oviedo, NW Spain). Environmental Earth Sciences, 68(2), 507-519. https://doi.org/10.1007/s12665-012-1755-3

• Pradhan, B., & Lee, S. (2010). Delineation of landslide hazard areas on Penang Island, Malaysia, by using frequency ratio, logistic regression, and artificial neural network models. Environmental Earth Sciences, 60(5), 1037-1054. https://doi.org/10.1007/s12665-009-0245-8

• Rucker, D. F., Crook, N., Glaser, D., & Loke, M. H. (2012). Pilot-scale field validation of the long electrode electrical resistivity tomography method. Geophysical Prospecting, 60(6), 1150-1166. https://doi.org/10.1111/j.1365-2478.2011.01039.x

• Szalai, S., Koppán, A., & Szarka, L. (2008). Effect of positional inaccuracies on multielectrode results. Acta Geodaetica et Geophysica Hungarica, 43(1), 33-42. https://doi.org/10.1556/AGeod.43.2008.1.3

• Tan, B. K. (1994). Engineering properties of granitic soils and rocks of Penang Island, Malaysia. Bulletin of the Geological Society of Malaysia, 35(July), 69-77. https://doi.org/10.7186/bgsm35199408

• Thabit, J. M., & Khalid, F. H. (2016). Resistivity imaging survey to delineate subsurface seepage of hydrocarbon contaminated water at Karbala Governorate, Iraq. Environmental Earth Sciences, 75(1), Article 87. https://doi.org/10.1007/s12665-015-4880-y

• Uhlemann, S., Chambers, J., Falck, W., Tirado Alonso, A., Fernández González, J., & Espín de Gea, A. (2018). Applying electrical resistivity tomography in ornamental stone mining: Challenges and solutions. Minerals, 8(11), Article 491. https://doi.org/10.3390/min8110491

• Zhou, B., & Dahlin, T. (2003). Properties and effects of measurement errors on 2D resistivity imaging surveying. Near Surface Geophysics, 1(3), 105-117. https://doi.org/10.3997/1873-0604.2003001