Study And Suppression Of Multiple Wave In Water Seismic Prospecting

As more and more large buildings such as bridges, piers, and dams are under construction nowadays, the engineering seismic prospecting which has played an important role in the land survey in the past are now extending to the field of water survey. It is mainly used in the identification of the thickness of overburden on riverbed and the depth of rivers or lakes. Other common uses of it include basement relief prospecting and the survey of the development feature of faulted structure. It is clear that the seismic prospecting is widely used in the water survey. The quality of the seismic prospecting depends largely on the choice of working parameters or methods as well as the level of signal-to-noise ratio. In order to make accurate geological interpretations or provide the engineering construction with faithful and detailed geotechnical datum, it is a matter of great urgency and necessity to study how to raise the resolution of prospecting and accuracy of interpretation by improving the technique of seismic exploration in every stage.Beginning with the basic theory of seismic prospecting, this article analyzes the geological condition of water seismic prospecting differing from the geological conditions on land and the advantages and disadvantages of water seismic prospecting at first. Then it discusses some issues about field data collection by the numerical method, such as the shooting intensity of source, the depth the source and the receiver sunk, the choice of receiver spacing and the maximal offset and so on. By some theoretical calculation, this article makes a clear conclusion about the best parameters for prospecting. The difficult of positioning, of course, also exists in the data acquisition in water, so the way of positioning over water must be different with the positioning on land in order to acquire high quality in filed data acquisition. The existing GPS positioning methods can basically meet the needs, so this article will introduce existing positioning method as well.Because multiple reflection interference is extremely serious in water seismic prospecting, this article will make some introductions in details of the basic theory and characteristics of multiple waves and how to recognize them. There are also some brief introductions about common methods to remove multiple waves. In order to attempt a kind of multiple rejection methods which base on wave equation, in this article, 2-D finite-difference method is used to get synthetic seismic records that with multiple waves coming from free interface. Then the author uses iteration inversion method that bases on feedback modeling to remove the simulated multiple waves. The ideal result shows the validity of this multiple rejection methods.Finally, in this article, the conventional multiple rejection methods are used in processing of observed data in engineering and achieve anticipated result which isverified by comparing with the exploration drilling.