SHALLOW WATER MULTIPLES DEPRESSION AND IMAGING ANALYSIS ON THE LAOSHAN UPLIFT OF THE SOUTH YELLOW SEA BASIN

The boundary between the Ceno-Mesozoic clastic deposits and the underlying Palaeozoic carbonate is a strong reflection interface on the Laoshan Uplift of the South Yellow Sea Basin. It acts as a strong shield to prevent the seismic waves from propagation downward, in addition to the multiples in the sea. As the results, deep seismic reflections are usually weak and difficult to image. Furthermore, there is lack of nearly offset reflected signals from seabed in shalloow water, the seabed related multiples can not be depressed effectively by conventional SRME (Surface Related Multiple Elimination) method. The Taup domain predictive deconvolution method always destroy valid reflected signals if the wave cycle is similar to the seabed multiple, particularly if the seabed is hard. The amplitude of the seabed multiple wave energy is stronger than the seabed reflection. In this case, the method of predictive deconvolution can not be used to depress seabed related multiples entirely. In this paper, seabed related multiples wave depression is performed by using the DWD + SRME combination method. DWD (Deterministic Water-layer Demultiple) method is used for attenuating short period seabed related multiples, and the SRME method is used for suppressing long period free surface related multiples. In addition, the method of Radon transform is also used for remove inter-layer multiples, so the multiples are depressed effectively, and thus deep reflection signals appear gradually. Trough the above mentioned seismic processing it is revealed that the Laoshan Uplift is a gentle anticline structure, and there are multiple thrust faults cutting through it. The Laoshan Uplift was embryonic in the Caledonian stage, formed in the Indosinian period and matured in the Yanshan period.