Study On Seismic Oceanographic Characteristics Of Bohai Strait

Seismic oceanography is a new developing method of studying physicaloceanographic phenomena and changes by using multi-channel seismic explorationmethods in recently years. Domestic and foreign experts use this method for the studyof physical ocean phenomena, such as marine fronts, mesoscale vortex, internalwaves, water body and thermocline, and get better results on it. Study areas are largerand more depth sea areas, just like Norwegian Sea and the Sea of Japan, but there isless study for the shallow sea of less than100m depth. Bohai Strait is an importantregional connection with the North Yellow Sea and the Bohai Sea, which also is animportant shipping roadway in the Bohai Sea, and Laotieshan waterway is particularlyimportant one. So the study of generation and variation of sea water body in theregion is significant impact on the ocean currents, water mess exchange,transportation and even military strategy. According to the physical oceanographycharacteristics of the ocean, the article studies the seismic acquisition systemparameters of water and data processing methods in the area of Laotieshan waterwaysof Bohai Strait.On the basis of physical oceanography and analysis of the relationship betweensound velocity, water density and temperature, salinity and depth that are physicalparameters of ocean, it is to establish a quantitative relationship between seismicreflection coefficients with various physical parameters. Combined with internationalequation of seawater state and Zoeppritz equation, it focuses on the relationshipbetween the various physical contributions to the reflection coefficient of ocean,establishing weak reflection seismic wave field characteristics of marine water body.Then on the basis of weak reflection seismic wave field characteristics, it comparesdifferent acquisiton parameters on the applicability of shallow water body thermocline reflection, and designs effective field seismic acquisition geometry which ensurethe affection of high resolution and high signal to noise ratio. For shallow seawater seismic data processing difficulties, vulnerable weak reflection signal by randomnoise, bad continuity of seismic events and weak amplitude of reflection, there is awave field separation method that is suitable for weak reflected signal and noise,which combines with data sparse transform idea by the use of multi-scale andmulti-resolution curvelet transform. The method is advantage for improving reflectiondata signal to noise ratio, and it can applied to process and to analyze the Bohai Straitwater reflection layer data.With application to multi-domain adaptive threshold curevlet transform toprocess shallow marine seismic data, it is effective suppress wideband random noiseand improve signal to noise ratio and resolution of the original data. Multi-domainidea overcomes the difficulty of choosing threshold that sets for denoising, then thereare good results in aspect of reasonable protecting signal and effective field separation.By using actual CTD data to synthesize seismic reflection signal as a well, itcompares with post-stack of corresponding reflection point. Results show that lateralresolution of stack seismic data is better than synthetic record, but the verticalresolution is slightly lower than CTD synthetic data, post-stack data of processing isimproved the signal to noise ratio and main frequency, both of them match wellwhatever is as a whole or as a detail. So post-stack data can be applied to the study ofphysical oceanographic phenomena and it also provide theoretical basis and exampleof seismic inversion and interpretation on shallow water properties.