Small scale high resolution multichannel seismic system surveys off Daishan Island
Bin Fang · 2008
The small scale array and high resolution multichannel seismic survey system,which is a more shorter streamer,shorter group interval,smaller air gun,shorter shot interval and higher frequency than traditional multichannel seismic survey system,has been used for the bridge project at Daishan Island for the selection of the well geology condition of bridge building site.Its group number of streamer is 24 with 2 meters of group interval.The volume of air gun is 10 in3 and shot offset is 46 meters.Frequency band range is from 1 to 1 000 Hz.In Daishan Island bridge project,we acquired high-precision seismic data using this method.The follow conlusion can be indicated through this study.Firstly,this system is suitable for the survey of shallow water and coast project.It is more convenient,practical and economic comparing with the traditional multichannel seimic system.Versus the singleseismic system,more detail reflection information of stratum from the seismic data is acquired.It's very suitable for the coastal region of the port,the bridge site,and other engineering project investigations.Secondly,in order to improve the resolution of seismic data for the interpretation,it is necessary to remove the coherent and random noise and to suppress the multiple wave and to correct the tidal difference.So these methods are used,which are F-K transformation,bandpass filter,dynamic correction and tidal correction.Finally,to compare with two survey site seismic data,we used an unified method and procedure to process and analyze the seismic data.Engineering geological condition of the two bridge design line has been acquired through the processing and interpretation of seismic data.Then the geological evidence was provided for proposal of bridge site and route.The 6 faults on the bridge design line No.1 and 5 faults on the No.2 have been interpreted,but all the faults can not cut cross the Quaternary stratum according to the seismic profile data,which means all faults are not active now.According to the motograhy data,this survey region does not have the seabed landside mass and other bad geological phenomenon with gentle seabed terrain.So this conclusion has been reached that the two design line sites have good geological conditions for the bridge building.We provide the seismic interpreted report to the design department of the bridge.The results of this study show that small scale high resolution multichannel seismic system survey may be an effective method to the shallow water engineering and environmental applications and sedimentary research.