Experimental Study On The Oceanic Internal Waves Induced By Seafloor Landslide

The South China Sea is the focus region of topographic research,energy exploration and geopolitics,due to its distinct geological structure and geographical location.The oceanic internal waves(OIWs)are a sort of common natural phenomenon which can interfere with the underwater acoustic communication and impact on the marine platforms as well as vessels.The OIWs-caused fluctuation of density thermocline and the variation of current field would influence the motion of underwater submersibles,or even lead to wreckage.There is a chronic density thermocline in the South China Sea,a region proved to be with an appropriate environment for the generation and propagation of OIWs.Seafloor landslides,as a crucial source of OIWs,are abundant in the southern slope of the South China Sea.Therefore,it is of great significance to further the investigation of OIWs induced by seafloor landslides.To carry out model experiments can facilitate the comprehension of the corresponding relation between the OIWs and seafloor landslides,and can acquire the mechanism and characters of OIWs induced by seafloor landslides.Based on the topography and ocean environment in the South China Sea,a physical experiment was conducted on OIWs induced by seafloor landslides.The characteristics and propagation of internal waves induced by traversing and non-traversing landslides were studied,and the influence factors were analyzed then.The main conclusions are as follows:(1)There is an evident difference in the time-series scale of internal waves induced by traversing and non-traversing landslides.The time series of internal waves induced by traversing landslides can be divided into steady section,mixing section and unsteady section.The volume-effect dominates in the steady section,and the wake-effect dominates in the unsteady section.The mixing section is subject to a joint effect of the both,and there is always an abrupt rise of the amplitude.However,the time series of internal waves induced by non-traversing seafloor landslides compromise of steady section and unsteady section only.(2)The characters of internal wave are affected by various factors.The amplitude of internal waves is determined by the profile,relative position and sliding velocity of the landslide body,and the traversing landslide can induce internal waves with larger amplitudes.The wave period is decided by the sliding velocity and slope angle of the landslide body under traversing scenarios,but in the non-traversing situations,the profile and initial position are the major factors.The wave speed is irrelated with the original disturbance of landslides,but will alter along the forward propagation.(3)The waveform maintains constant in the propagation process.After a propagation of 90 mm,whereas the wave speed increases 26% and the height of the first wave decreases 25% generally.