1. Figure 1 (from Fowler p 120
The configuration for the 110N 36 channel active source refraction survey:
Long survey: Source is at x=0, geophone #1 is at 1m, #36 is at 28m
Short survey: Source is at x=0, geophone #1 is at m, #36 is at 14m
Record sections 1+3
Ground roll (Rayleigh wave) slope 1/(0.92*ß_1)
18m
18m
X_cross is this distance at which the direct wave and the refracted wave arrive at the same time. X_c is the distance where you will start seeing head waves arriving. At this distance the head wave has a segment AB that has zero length (so it is a reflected wave with incidence angle i_critical). ß1 is the shear wave velocity for the upper layer. The Rayleigh wave takes a ray path SR in the upper layer.

2. Distance from source (m)
Which way is up?
Time after shot (ms)
0.5
Distance from source (m) 18
milliseconds
New Record Section 1: Shooting North, source 0.5 m from first geophone, 0.5 m spacing between geophones

3. Distance from source (m)
Which way is up?
Time after shot (ms) 18
Distance from source (m)
0.5
milliseconds
New Record Section 2: Shooting South, source 0.5 m from first geophone, 0.5 m spacing between geophones

4. Distance from source (m)
Which way is up?
Time after shot (ms)
0.3889
Distance from source (m) 14
milliseconds
Record Section 3: Shooting South, source m from first geophone, m spacing between geophones