3D Inversion Modelling of Gravity Data for Identification of Subsurface Structures in the Mud Volcano Area of Sedati, Sidoarjo

Many mud volcanoes are found in Central Java and East Java in the north, but research on mud volcanoes is still limited. This research focuses on the Sedati mud volcano area, Sidoarjo with a research area of 500x400 meters. Measurement of gravity method data with 88 points spaced 50 meters to determine the value of rock density and subsurface structure of Sedati mud volcano area. From the data that has been obtained, data processing is carried out to obtain a map of the distribution of regional and residual gravity anomaly values. From the anomaly data, 3D inversion was carried out to obtain a map of the subsurface structure. The 3D gravity inversion modelling results show that there is high density rock block which is interpreted as a basin that holds the reservoir from the mud volcano. Near the surface and around the mudflow in the study area, the distribution of low density is caused by the presence of mud content. There is a possibility that there is a fault zone with a west-east direction from the study area. The results of the 3D gravity model incision show that the weak zone in the study area is a zone of accumulation of mud which has a density value of 1.8 g/cm 3 at a depth of 20 meters to 500 meters.