Interpretation of gravity data of the Bromo-Tengger Volcanic Complex (Indonesia) based on geostatistical analysis

Abstract

An accurate gravity map provides fundamental data for geoscience research and enables accurate subsurface interpretation. For many years, prior gravity surveys in the Bromo‑Tengger volcanic complex have been unsuccessful in accurately defining rock units, structural continuity, and caldera boundaries. This study analyzed a residual gravity anomaly map produced through geostatistical analysis to overcome these limitations, which forms the basis for subsequent geological interpretation. Geostatistical analysis revealed that the Gaussian variogram model best fits the residual gravity map. This model fulfilled the minimum residual sum of squares and a mean squared deviation ratio of 0.998, which is close to the ideal value of 1. This model produced a more precise image of the subsurface geology than previous studies and accurately identified previously unmapped positive anomalies on volcanic cones and visibly defined the boundaries of the Tengger Caldera, the Cemorolawang Wall lineament, and the estimated depth of the caldera basement. This study identified elevated residual gravity values in the Tengger volcanic rocks and lower values in the young cone complex pyroclastic deposits, which constitute the primary caldera‑filling material. The interpretation of this study’s results will contribute to future geoscience studies related to the Bromo‑Tengger volcanic complex (Indonesia).