If the earth quake caused the emission of methane gas,the plane would fall from the sky,and ships will not float on methane gas ,even a small amount of methane upsets the H20 [water]balance on which ships float,,this is what is behind the Bermuda triangle.......earthquakes erupt tons of methane,any ship over area sinks,so fall any plane,,,they fall/sink onto ocean floor,the dust settles after the eruption completely covering all trace of objects caught in maelstrom...even balsa wood will not float on methane