2025-02-07 ペンシルベニア州立大学(PennState)
＜関連情報＞
- https://www.psu.edu/news/earth-and-mineral-sciences/story/satellite-data-identifies-warning-signs-ahead-2018-volcanic
- https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GL112296
インドネシア、アナク・クラカタウの2018年崩壊に先立ち、衛星測地学が剥離断層に15mの滑りを発見 Satellite Geodesy Uncovers 15 m of Slip on a Detachment Fault Prior to the 2018 Collapse at Anak Krakatau, Indonesia
Young Cheol Kim, Christelle Wauthier, Thomas R. Walter
Geophysical Research Letters Published: 16 November 2024
DOI:https://doi.org/10.1029/2024GL112296
Abstract
On 22 December 2018, parts of the Anak Krakatau edifice collapsed, triggering a deadly tsunami. To investigate pre-collapse surface displacements, we analyzed Interferometric Synthetic Aperture Radar satellite geodetic data from 2006 to 2018, acquired from ALOS-1 (2006–2011), COSMO-SkyMED (2012–2018), and Sentinel-1 (2014–2018). We identified line-of-sight displacements on the southwestern flank throughout the study period. Inversion of COSMO-SkyMED data revealed a rectangular dislocation with a cumulative slip of 12 m from April 2012 to December 2018. Fixing the fault geometry, we found the optimal slip for time periods corresponding to slip rate changes, ranging from 1.2 to 3.1 m/yr. The slip estimates for ALOS-1 and Sentinel-1 data were 0.88 m/yr and 1.1 m/yr, respectively, over their individual time periods. Overall, the detachment fault experienced approximately 15 m of slip from 2006 to 2018 with acceleration and deceleration periods, and a notable acceleration prior to the 2018 collapse.
Key Points
- InSAR time series show ground motion away from the satellite on the southwest flank of Anak Krakatau for the period 2006–2018
- The signal is likely induced by long-term normal slip on a preexisting detachment fault which slipped rapidly in 2018 causing a collapse
- The surface displacements and slip rate involve accelerations and decelerations, with a major acceleration right before the collapse
Plain Language Summary
In this study, we investigated the changes that occurred on Anak Krakatau volcano before its collapse on 22 December 2018. We used satellite data from three different sources; ALOS-1, COSMO-SkyMED, and Sentinel-1, covering the period from 2006 to 2018. Our analysis revealed that the southwestern side of the volcano was moving over time from 2006 to before the collapse in 2018. By examining data from COSMO-SkyMED, we found that there was a rectangular area where the ground shifted by about 12 m. We investigated detailed movement and calculated that the ground slipped at different rates over time, ranging from 1.2 to 3.1 m per year. Data from ALOS-1 and Sentinel-1 gave us slightly different slip estimates and rates. Overall, our findings show that the deeper part of the ground moved around 15 m in total from 2006 to 2018 with varying speed and a significant acceleration before the 2018 collapse occurred.
