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| | Abstract | | It has been known that multi-basalt layers separated by sediments are identified in Voring Basin off Norway by ODP site 642. The presence of such basalt layers is also identified in Faeroe-Shetland Basin in the Atlantic Ocean. Although the sub-basalt sediments layers have been thought to be high potential oil reservoir, it is extremely difficult to identify the sub-basalt structure by conventional analysis for the surface seismic reflection survey. Using OBS data with more than 30km offset in the Atlantic Ocean, the reflected and refracted arrivals from the sub-basalt have been identified in the wide-angle reflections with shadow zone. Based on the authors expertise in identifying and interpreting similar phases in the other areas, we analyzed two 100km seismic survey data with 10km-long streamer. In shot gather records of the sub-basalt region, the reflected and refracted signals for the top basalt layer disappear quickly and those for the second basalt layer appear with time-delayed large amplitude phase. Using this method, we obtained Vp structure of top and sub-basalt layers. |
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