Figure 4

source after a hole was drilled at a depth of 15Â m, (e) Combustible ice samples obtained by drilling 8Â m underground at drill holes-3, (f) The burning process of Combustible ice samples on site.
Drilling results and combustible ice samples in study area R-1. (a) Location of the drill hole, the surface methane concentration sensor, the ground temperature sensor, and the measurement range of the high-density electrical method (HDR) and the ground-penetrating radar (GPR) in the study area R-1, (b) High-concentration methane bubbles under the ice surface at the drilling site in spring, (c) High-concentration methane gas discharged along the drill pipe as found by a light drilling machine near borehole 4 (up to 10,000Â ppm measuring instrument upper limit; the measuring instrument is an SKZ1050-CH4 methane detector), (d) The flame formed in contact with a fire