Question

The fold of a 2D seismic survey is defined as the maximum number of traces in which one of the following gathers?

• A. Common midpoint gather
• B. Common offset gather
• C. Common shot gather
• D. Common receiver gather

Hint:

Always remember: Fold = number of traces per CMP. Increasing fold enhances seismic image clarity by improving the signal-to-noise ratio.

Answer 1

The Correct Option is A

Step 1: Understanding seismic fold. In seismic surveys, the \emph{fold} is defined as the number of seismic traces that are stacked together to represent the same subsurface reflection point. A higher fold improves the signal-to-noise ratio and enhances data quality. Step 2: Identifying the relevant gather. - A common shot gather groups traces recorded from one source point with multiple receivers. It represents data for a single shot location, not reflection redundancy.
- A common receiver gather groups traces recorded at a single receiver from multiple shot points. It also does not define the fold. - A common offset gather groups traces with the same source–receiver distance. This is useful for velocity analysis but not directly related to fold definition.
- A common midpoint (CMP) gather groups all traces that share the same midpoint between source and receiver. Since multiple source–receiver pairs can correspond to the same subsurface reflection point, the number of traces in a CMP gather defines the \emph{fold}. Step 3: Conclusion. The fold of a 2D seismic survey is therefore defined as the maximum number of traces in a common midpoint gather. \[ \boxed{\text{Common Midpoint Gather}} \]