Determination of Geoelectrical Strike To Investigate The Geological Structures In Surabaya And Gresik Areas

The Magnetotelluric data acquisition is performed with a certain coordinate system orientation, thus the possibility of the field measurement data would be not proper with the geological strike direction. Therefore, the information of geoelectrical strike is needed to enhance the quality of Magnetotelluric data interpretation where if the data had the similar direction with the geological strike thus it will be properly sufficient with the actual subsurface condition. A magnetotelluric study by utilized polar diagram was conducted to analyze the orientation of geoelectrical strike that are correlated with the geological structures in the Surabaya and Gresik areas. However, polar diagram analysis using phase tensor data has an ambiguity of +90° therefore additional analysis is carried out using tipper data. The results showed the geoelectrical strike direction is N315°E and it is slightly similar with the strike trend of geological structures anomaly. Meanwhile, the geological structures is generally characterized by low to medium value of resistivity contrasts around 30-500 ohm.m consisting of the Surabaya Kendeng Fault, Kendeng Kedung Waru Fault, anticline, and other expected faults.