Movement and backscatter intensity analysis of fairy circles (Sao Francisco Basin, Brazil) from the processing of Sentinel-1 SAR-images
Description
A natural hydrogen emission was discovered in the Campinas fairy circle in the Sao Francisco Basin (Brazil) [Prinzhofer et al., 2019, doi in the links]. This type of hydrogen emissions in the form of rounded circular depressions occur in continental cratonic areas. The Campinas fairy circle is surrounded by numerous similar structures, but only this and another structure (called Baru) show significant hydrogen emission. We used radar interferometry and radar backscatter to map and characterize ground motions and vegetation / soil moisture during active hydrogen venting at the Campinas site and surrounding area rich in fairy circles. For the processing, satellite images from Sentinel-1 (ESA, C-band) were used. Only descending images of the area are available (taken by the S1B satellite). 3 bursts from IW1 (VV polarisation) were selected for processing. This was an SBAS-based processing (made by author CsSz). The Gamma software was used for the processing, the steps of the demo PALSAR1 SBAS Yibal from Gamma software were taken into account. A cutout from the result is available in the corresponding folder (it can be loaded into MatLab, please read the ‘readme.txt’). A description of the steps is also available in the corresponding folder. The cutout was made because the area of interest (which is the focus of the processing) is surrounded by rivers - this makes the other parts of the processing unreliable. Results show ground motions with up to 1 cm/year (in line-of sight velocity). Within this area, the subsidence of the central part of the Campinas fairy circle implies the active formation of the structure during hydrogen emission. SAR backscatter analysis performed over a larger area is detailed in the corresponding folder. For further information see: Békési, E., Prinzhofer, A., Porkoláb, K., Tari, G., Szárnya, C.,: Exploration and monitoring of "fairy circles" associated with natural hydrogen seepages with synthetic aperture radar interferometry and backscatter analysis in the São Francisco basin (Brazil). Under review in the International Journal of Hydrogen Energy.
Files
Steps to reproduce
The software 'Gamma' was used to process the satellite images (Sentinel-1). For SBAS processing and various corrections, the steps and methods of Gamma demo: PALSAR1_SBAS_Yibal were used. See 'Technical_details_of_the_SBAS-processing' folder for detailed information. The 'Steps_of_processing.txt' contains the description of the general processing.