Near Surface Geophysics > 3D Imaging
  • Step 1: The seismic spread.
    The seismic spread is composed of a receiver spread and a source spread. The receiver spread , displayed in green, is composed of 2 receiver lines. Receiver line direction is called the in-line direction. Distance between receiver lines is 4 m. There are 24 geophones per line. Distance between geophones is 2 m.
    The source spread , displayed in yellow, is composed of 11 source lines oriented perpendicularly to the receiver lines. 11 shots are fired per line. Distance between shots is 2 m. Distance between source lines is 4 m. The source lines and the receiver lines are oriented perpendicularly.
    The distance between receiver spread and source spread is 4 m. There is no overlap between the source and the receiver spread.
    The listening time is limited to 250 ms, the sampling time interval is 0.5 ms.

  • Step 2: Seismic fold.
    Due to the geometry of acquisition, the geometry fold is symmetric. The picture shows the fold variation. It varies from 0 to 22. In the display, the horizontal axis is the in line direction. The vertical axis is the cross line direction.

  • Step 3: Example of a 3D shot point.
    You can see the refracted wave, the reflected wave, the air wave and the surface wave. The air wave is aliased.