Integrated Magnetic and Gravity Methods to Delineate Subsurface Structures of the Wringinanom Mud Volcano, East Java

Wringinanom Mud Volcano is an interesting geological feature in Kendeng zone, East Java. Its presence is often associated with subsurface petroleum systems and active tectonic dynamics, particularly the activity of the Kendeng Fault, a major geological structure in the region. This study aims to analyze the Wringinanom mud volcano system by integrating magnetic and gravity methods to understand the subsurface geological structures that control the appearance of mud vulcanoes. Geophysical data measurements were conducted at 180 points for the magnetic method and 47 points for the gravity method using a Lacoste Romberg relative gravimeter, distributed around the mud volcano area. The results of magnetic data analysis indicate anomaly values ranging from-1044.1 to 692.3 nT, with a low anomaly characterizing the mud volcano area, and material distribution extending to the north, west, and south. In addition, two suspected fault zones trending NE-SW and NW-SE were identified, marked by gradients between high and low magnetic anomalies. Gravity data in terms of complete Bouguer anomaly (CBA) values range from-4.1 to 0.6 mGal, showing local anomalies that indicate lower subsurface density beneath the mud volcano compared to surrounding areas. Further analysis using the First Horizontal Derivative (FHD) filter identified a possible NW-SE trending fault crossing the mud volcano area, consistent with the findings from the magnetic method. The integration of both geophysical methods emphasizes the significant role of geological structures, especially fault systems, in controlling the appearance of the Wringinanom mud volcano. This study contributes to the limited knowledge of mud volcano systems in Java and highlights the need for further investigation, particularly through detailed subsurface modeling and fault pattern identification.