Double bottom simulating reflectors and tentative interpretation with implications for the dynamic accumulation of gas hydrates in the northern slope of the Qiongdongnan Basin, South China Sea

•Double bottom simulating reflectors are first imaged on submarine canyons in the Qiongdongnan Basin.•Mechanism of the formation of double bottom simulating reflectors is explored based on phase equilibrium simulation.•Gas hydrate/ gas hydrate and free gas are speculated to be present beneath the BSR1.•Double bottom simulating reflectors indicate dynamic formation and evolution of the gas hydrate system.