The effect of inhomogeneous water on seismic imaging in deepwater areas of the South China Sea

Lili Ji,Tianyao Hao,Mian Lin

doi:10.1007/s11434-013-5975-z

Abstract

This paper examines the effect of inhomogeneous water on seismic imaging in deep water areas. An appropriate partial differential equation is derived for the acoustic pressure field in inhomogeneous water, including current effects. Seismic wavefields are simulated and the results show that the traveltime of seismic waves can be affected. The maximum traveltime perturbation at zero offset is 20 ms. In particular, the structure of horizontal reflectors below the water is distorted by mesoscale eddies. Variations of water temperature are the fundamental cause of the distortion. Finally, a calibration method for the distortion of seismic imaging caused by inhomogeneous water is presented.

Highlights

This paper examines the effect of inhomogeneous water on seismic imaging in deep water areas
Since 2009, with the support of the National Natural Science Foundation of China and the National Basic Research Program of China, we have studied the following issues: (1) To what degree is seismic imaging influenced by inhomogeneous water? (2) What causes this influence? (3) How can the influence of the inhomogeneous water be eliminated from seismic data? The above three problems will be answered in this paper
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Summary

To what degree is a seismic image influenced by inhomogeneous water?

An appropriate partial differential equation is derived for the acoustic pressure field in inhomogeneous water, including current effects [15]. As the seismic wave travels through the cold-core eddy, the inhomogeneous velocities of the cold-core eddy cause weak reflected waves (Figure 2). The amplitude of these weak reflected waves is of the order of 10 4, while the amplitude of the reflections from the reflectors below the water is of the order of 10 2. To study more clearly the effect of inhomogeneous water, we expand the research region to the affected area of the cold-core eddy (300 km) and calculate the zero-offset seismic profiling of H1 for homogeneous water, static water and the cold-core eddy (Figure 4). The depth of the reflector is shallower than the real depth of the reflector in the perturbation of the cold-core eddy and it is deeper than the real depth of the reflector in the perturbation of the warm-core eddy

What causes the influence of the inhomogeneous water on seismic imaging?

How can the influence of inhomogeneous water be eliminated from seismic data?