3D model of Krakatau volcano subsurface structure based on gravity data

Krakatau is one of the volcano in Indonesia which has the destructive paroxysmal eruption. Eruption on 1883 was estimated had VEI of 6. The eruption was recorded as one among some most violent volcanic eruption event in the world. Gravity method is one of the geophysical methods that could delineate the subsurface structure base on density variation. Therefore, the objectives of this research are to reconstruct the 3D subsurface structure of the Krakatau volcano especially the approximate location and dimension of the magma chamber. The subsurface model of Krakatau was done by 3D modelling using residual anomaly map. In order to develop the status of magma chamber model, the available information on the geological map of Krakatau and surrounding area was used. Besides that, some information relative to the volcano such as the information derived from earthquake wave attenuation were utilized. The result of the study shows that position its volcano magma chamber is not directly vertical or oblique under the volcano crater and it has multiple chambers which trending northwest-southeast.