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# Subsurface Model

To illustrate the method, I created a simplified subsurface model corresponding to a target horizon whose depth changes from about 0.3 km to about 2 km. The model simulates a land prospect, has high local dips and mild topography. Figures  and  show views of the model from the inline and the cross-line direction respectively. The model has significant dips in both directions. Similarly, Figures  and  show views of the target horizon from the inline and the cross-line direction. There are two possible reservoirs in this horizon, one at the top and one in the small structure to the right (Figure ). The model is 10 km x 10 km with a maximum depth of about 3 km. The velocity field consists of blocks delimited by the reflectors. Within each block the velocity changes laterally as well as vertically in a gradient-based fashion as summarized on Table 1. Velocity at each point of each block is computed as .

model1
Figure 1
Subsurface model. View from the strike direction. The horizontal dimensions are 10 km x 10 km. The depth of the deepest reflector is 3 km.

model2
Figure 2
Subsurface model. View from the dip direction. The horizontal dimensions are 10 km x10 km. The depth of the deepest reflector is 3 km.

 target1 Figure 3 Target reflector. View from the dip direction. The reservoir corresponds to the top of the structure at a depth of about 0.3 km.

 target2 Figure 4 Target reflector. View from the strike direction. The reservoir corresponds to the top of the structure at a depth of about 0.3 km.

 Block Reflectors v0 1 1 and 2 2000 0.01 0.05 0.5 2 2 and 3 3000 0.05 0.01 0.2 3 3 and 4 2400 0.01 0.01 0.5 4 4 and 5 3600 0.05 0.01 0.1 5 5 and 6 5000 0.0 0.0 0.0

Next: Standard 3-D Survey Design Up: Alvarez: 3-D survey design Previous: Introduction
Stanford Exploration Project
7/8/2003