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Earth, Planets and Space
Fig. 2 | Earth, Planets and Space

Fig. 2

From: A new seismic survey technology using underwater speaker detected a low-velocity zone near the seafloor: an implication of methane gas accumulation in Tokyo Bay

Fig. 2

a Location map of the seismic experiment conducted in December 2017. The survey area is located at the northernmost part of Tokyo Bay. The white contour lines and two-digit numbers represent water depths. b Resulting seismic reflection profile, which was stacked by a constant velocity of 1500 m/s. Blue color indicates positive amplitude and red color indicates negative amplitude. c Fish finder images that suggest the presence of a gas foaming phenomenon, observed at location A (see a) by T/V Hiyodori in the spring of 2017. The colors in the fish finder images represent the reflection strength of either the fish or seabed: Warmer colors indicate higher strength and colder colors indicate lower strength. The colors in the seabed classification section represent lithology: Gray, orange, red and brown colors show mud, sand, gravel and rock facies, respectively

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