2:15 PM - 2:30 PM
[ACC28-02] Evaluation of permafrost distribution at north cirque of Mt. Shakushi, in the northern Japanese Alps
Keywords:Mountain permafrost, Rock glacier, DInSAR analysis, GPR, Electrical resistivity
Differential interferometric SAR analysis using SAR data from two-month, one-year, and two-year observation periods showed that rock glacier surface changes were observed in all periods. The amount of movement was several centimeters in one year and more than ten centimeters in two years, indicating continuous flow. These results suggest that there is a high possibility that permafrost exists in the rock glacier.
Next, we conducted a ground-penetrating radar survey at a location 100 m upstream from the terminus of the rock glacier, which was considered to have the highest flow rate by differential interferometric SAR analysis. As a result, the base was found at a depth of 10 to 12 meters, and the interior was composed of three layers. The depth of the rock glacier is about 12 m. The surface layer is composed of angular gravel of siliciclastics, and the upper and lower layers are composed of different materials mixed with gravel.
To confirm the composition of the three layers inside the rock glacier observed by the ground-penetrating radar survey, a two-dimensional electrical resistivity survey was carried out in the same survey line. As a result, a part with a resistivity value of 10^4 to 10^5 Ωm, which is an indicator of permafrost, was detected in the area around 10 m from the ground surface. The resistivity values of 10^4 to 10^5 Ωm, which are indicators of permafrost, were detected from the surface to a depth of 10 m. The resistivity value of the rock glacier was lower than 8×10^3Ωm below 12m depth. This result suggests that there is a high possibility that mountain permafrost exists inside the rock glacier.