5:15 PM - 7:15 PM
[HRE12-P12] Observation and analysis of surface changes in the fairy circle and surrounding area using InSAR
Keywords:Natural Hydrogen, Fairy Circle, SAR
Hydrogen is expected to be widely adopted as a zero-emission fuel in the transition to a decarbonized society, and interest in natural hydrogen as a future hydrogen supply source is growing. Natural hydrogen has been identified in locations such as mid-ocean ridges and ophiolite zones on land, often forming characteristic depressions when it seeps to the surface. These depressions, known as fairy circles, serve as important indicators for natural hydrogen exploration, and the presence of natural hydrogen has already been confirmed worldwide.
The hydrogen concentration in the gas leaking from fairy circles has been recorded as highest on the outer slopes of the peripheral areas and moderate inside the circles. This suggests that the peripheral areas serve as preferential discharge zones for hydrogen-rich fluids migrating toward the surface. While the formation mechanism of the peripheral areas and their relationship with higher hydrogen concentrations remain unclear, they may be associated with fault networks surrounding the terrain and unique petrological characteristics.
To investigate geological changes in fairy circles, this study analyzed subtle surface deformations in and around fairy circles identified in Brazil's São Francisco Basin and Western Australia using satellite images obtained from interferometric synthetic aperture radar (InSAR). Data spanning five years (2016–2021) were used for Brazil, while data spanning nine years (2016–2025) were used for Western Australia. The São Francisco Basin in Brazil is primarily composed of Archean basement rocks, granites, mafic to ultramafic intrusions, and mafic intrusive rocks. Western Australia, consisting mainly of three stable cratons, includes the Yilgarn Craton, the study area, where the north-south trending Pinjarra Orogen and an east-west fault system with mafic dikes have developed.
As a result, no significant surface changes were observed in Brazil. However, in Western Australia, subsidence was confirmed in many fairy circles. The observed subsidence was classified into two types: cases where the entire depression subsides and cases where only the peripheral areas subside. The former is considered to be in the process of forming a fairy circle, while the latter suggests that the formation of the fairy circle is complete, with only the peripheral areas subsiding due to the generation of natural hydrogen.
The hydrogen concentration in the gas leaking from fairy circles has been recorded as highest on the outer slopes of the peripheral areas and moderate inside the circles. This suggests that the peripheral areas serve as preferential discharge zones for hydrogen-rich fluids migrating toward the surface. While the formation mechanism of the peripheral areas and their relationship with higher hydrogen concentrations remain unclear, they may be associated with fault networks surrounding the terrain and unique petrological characteristics.
To investigate geological changes in fairy circles, this study analyzed subtle surface deformations in and around fairy circles identified in Brazil's São Francisco Basin and Western Australia using satellite images obtained from interferometric synthetic aperture radar (InSAR). Data spanning five years (2016–2021) were used for Brazil, while data spanning nine years (2016–2025) were used for Western Australia. The São Francisco Basin in Brazil is primarily composed of Archean basement rocks, granites, mafic to ultramafic intrusions, and mafic intrusive rocks. Western Australia, consisting mainly of three stable cratons, includes the Yilgarn Craton, the study area, where the north-south trending Pinjarra Orogen and an east-west fault system with mafic dikes have developed.
As a result, no significant surface changes were observed in Brazil. However, in Western Australia, subsidence was confirmed in many fairy circles. The observed subsidence was classified into two types: cases where the entire depression subsides and cases where only the peripheral areas subside. The former is considered to be in the process of forming a fairy circle, while the latter suggests that the formation of the fairy circle is complete, with only the peripheral areas subsiding due to the generation of natural hydrogen.