(Special session) Resource exploration and big-data processing［Wed. Sep 13, 2023 AM Room-1］

[2101-04-03] [Student presentation: Doctoral course] Comparison of geological structures derived from satellite- and ground survey-based gravity data for interpreting geothermal system

○Angga Bakti Pratama^1,2, Katsuaki Koike¹ (1. Kyoto University, 2. Institut Teknologi Bandung)

Chairperson: Taiki Kubo (Kyoto University), Tatsu Kuwatani (JAMSTEC), Akihisa Kizaki (Akita University)

Keywords:TOPEX, GGMPlus, Talaga Field, Geological Structure

Satellite gravity data have been widely used to obtain preliminary information on basement structure and combine them with other geoscience and field survey data. However, accuracy of satellite gravity data has not yet been evaluated in detail by comparing the data with ground gravity survey data and actual geologic structures. For this issue, this study aims to evaluate the accuracy of two different satellite gravity data (Topex and GGMPlus) and the capability of delineating geologic structures by referring to the structures estimated through the ground survey gravity data in the Talaga geothermal field, Central Java, Indonesia. Geological structures are delineated by the data reduction at first and then enhancement methods to enhance gravity anomaly. Because the satellite gravity data, which are open-source data, are provided in the form of free air anomaly, the data processing step is fewer than that of the ground survey gravity data. The satellite- and ground-based gravity data are then transformed into the Completed Bouguer Anomaly (CBA) through the Bouguer and terrain corrections and finally, the gradient analysis is implemented to enhance the CBA and delineate geologic structures from it. The two satellite gravity data generated similar patterns of CBA that is probably caused by a large caldera structure and the density contrast between the inside and outside of caldera. This CBA feature also appeared in the result of ground gravity data, which confirmed that the Talaga geothermal system is controlled by the caldera structure. Although the density patterns were generally agreeable between the satellite- and ground-based gravity data, local features and structures were detected from the ground data only. Therefore, satellite-based data must be used for detecting regional structures due to the limitation of spatial resolution.