EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

High-resolution InSAR reveals deformation inside the crater of Agung, Indonesia, prior to the 2017 eruption.

Mark Bemelmans1,2, Juliet Biggs1,2, James Wookey1, Mike Poland3, Susanna Ebmeier2,4, and Devy Syahbana5
Mark Bemelmans et al.
  • 1University of Bristol, Faculty of Science, School of Earth Sciences, Bristol, United Kingdom
  • 2COMET, Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics, United Kingdom
  • 3U.S. Geological Survey, Cascades Volcano Observatory, Vancouver (WA), United States of America
  • 4University of Leeds, Faculty of Environment, School of Earth and Environment, Leeds, United Kingdom
  • 5Center for Volcanology and Geological Hazard Mitigation, Indonesia

In September 2017, volcanic unrest in the vicinity of Mount Agung, Bali, Indonesia, increased drastically as a dike intruded between Agung and Batur volcanoes. This intrusion was followed by 5 weeks of declining activity before the eventual explosive eruption from Agung’s summit starting on November 21, 2017. We use high-resolution satellite SAR imagery to detect pre-eruptive intra-crater uplift at Agung volcano. We show that deformation of the crater floor occurred together with the dike intrusion to the northwest of the volcano. We attribute the deformation to a hydrothermal system less than 300 m below the surface that was activated by the injection of magmatic gasses. This finding indicates that Agung’s shallow magmatic system was active from the start of the increased unrest. Additionally, we observe a pulse of intra-crater uplift within 3-0.5 days prior to the onset of the eruption. The second pulse of uplift was one of the only precursors to the eruption and was probably caused by interaction between the hydrothermal system and the ascending magma. The detection of localized deformation during a volcanic crisis has important implications for eruption and unrest forecasting at Mount Agung and similar volcanoes and argues for monitoring with high-resolution SAR, which is capable of achieving both outstanding spatial resolution and, if sufficient satellites are used, excellent temporal coverage.

How to cite: Bemelmans, M., Biggs, J., Wookey, J., Poland, M., Ebmeier, S., and Syahbana, D.: High-resolution InSAR reveals deformation inside the crater of Agung, Indonesia, prior to the 2017 eruption., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3883,, 2022.