Abstract
During a volcanic crisis, high-rate, localised deformation can indicate magma close to the surface, with important implications for eruption forecasting. However, only a few such examples have been reported, because frequent, dense monitoring is needed. High-resolution Synthetic Aperture Radar (SAR) is capable of achieving < 1 m spatial resolution and sub-weekly revisit times, but is under-used. Here we use high-resolution satellite SAR imagery from COSMO-SkyMed, TerraSAR-X and Sentinel-1 to detect intra-crater uplift preceding the November 2017 onset of eruptive activity at Agung, Indonesia. Processing the SAR imagery with an up-to-date, accurate, high-resolution digital elevation model (DEM) was crucial for preventing aliasing of the deformation signal and for accurate georeferencing. We show that > 15 cm of line-of-sight shortening occurred over a 400-by-400 m area on the crater floor in September-October 2017, accompanying a deep seismic swarm and flank dyke intrusion. We attribute the deformation to the pressurisation of a shallow ( < 200 m deep) hydrothermal system by the injection of magmatic gases and fluids. We also observe a second pulse of intra-crater deformation of 3-5 cm within 4 days to 11 hours prior to the first phreatomagmatic eruption, which is consistent with interaction between the hydrothermal system and the ascending magma. This phreatomagmatic eruption created the central pathway used during the final stages of magma ascent. Our observations have important implications for understanding unrest and eruption forecasting, and demonstrate the potential of monitoring with high-resolution SAR.
| Original language | English |
|---|---|
| Article number | e2022JB025669 |
| Journal | Journal of Geophysical Research: Solid Earth |
| Volume | 128 |
| Issue number | 5 |
| Early online date | 27 Apr 2023 |
| DOIs | |
| Publication status | Published - 9 May 2023 |
Bibliographical note
Funding Information:We thank Francisco Delgado, Jeremy Pesicek, and one anonymous reviewer for their thoughtful comments, which helped raise the quality of this work. We would also like to thank our colleagues at the USGS and CVGHM for their support and helpful discussion. We want to thank VDAP for providing the mosaic of the TSX and WV3 DEM over Agung. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. MJWB, JB and SKE are members of the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET, http://comet.nerc.ac.uk), a partnership between UK Universities and the British Geological Survey. We want to thank COMET for their support and the use of their resources. MJWB is funded by the NERC GW4+ doctoral Training Partnership (S100413-110). For this project (JB) has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement 101003173), JB is also funded through the Leverhulme Prize (PLP-2018-362). SKE is funded by a NERC Independent Research Fellowship (NE/R015546/1).
Funding Information:
We thank Francisco Delgado, Jeremy Pesicek, and one anonymous reviewer for their thoughtful comments, which helped raise the quality of this work. We would also like to thank our colleagues at the USGS and CVGHM for their support and helpful discussion. We want to thank VDAP for providing the mosaic of the TSX and WV3 DEM over Agung. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. MJWB, JB and SKE are members of the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET, http://comet.nerc.ac.uk ), a partnership between UK Universities and the British Geological Survey. We want to thank COMET for their support and the use of their resources. MJWB is funded by the NERC GW4+ doctoral Training Partnership (S100413‐110). For this project (JB) has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement 101003173), JB is also funded through the Leverhulme Prize (PLP‐2018‐362). SKE is funded by a NERC Independent Research Fellowship (NE/R015546/1).
Publisher Copyright:
© 2023. The Authors.