| Summary: | 碩士 === 國立臺灣大學 === 海洋研究所 === 106 === According 2D seismic acquisitive equipment to produce 3D seismic image by streamer feathering, dense 2D seismic survey and precise GPS system which setting on the tail buoy at the end of seismic cable.
The Southern Okinawa Trough (SOT) is the back arc basin behind the Ryukyu subduction zone, which is the youngest rifting region with highly geothermal activities. The highly geothermal value may suggest the strong hydrothermal circulation in this area. Hydrothermal mineral deposits consist of rare earth elements are formed in situ through hydrothermal alternation. For further understanding, the 3D seismic image play an important role in geophysical investigation, which could picture a reality of geological structures distributed underground.
The 3D seismic data used in this research was collected unpredictably during the cruise where there was a strong Kuroshio Current passing through the east site of Taiwan. The strong current affected the seismic cable, causing seismic cable feathering. The seismic cable feathering induce incorrect seismic data. To fix this flaw, data acquisition pattern during the cruise needed to be changed from original survey. Under the premise that the original seismic data convert into dense 2D seismic lines with the interval around 340 meter, GPS data of seismic traces should be calculated. With such kind of improvement, the flaw in 2D seismic data processing become an advantage in 3D seismic data processing.
3D seismic image processed with the steps in this research, could show a distinct seismic image to reveal igneous intrusion and normal faults development in the rifting region of SOT. The normal faults which cut through the igneous intrusion may be a pathway of fluid migration. After the processing steps that applied in my research, high quality 3D seismic images could be processed by only 2D seismic acquisitive equipment.
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