1. Indoor mapping exercise Plotting information from seismic profiles on to a map

2. Seismic profiles are 2D images of the subsurface but the view they give can be compared to a rock outcrop such as a cliff exposure in the field, only on a much bigger scale. This exercise plots information from seismic profiles on to a map and is good practice for field mapping and visualizing structures in 3D.

3. Steps 1-4

4. N 8009001000110012001300140015001600 600 800 1000 1200 400 200 0 TWT (msec) CMP 2 km Line name: SSR-1 ✂ Cut here to 600msec 0 600 800 1000 1200 400 200 Mark the position of the hinge 1. Trace the line of each limb to see where they meet. 2. Measure the interlimb angle and mark the centre point. Hinge for horizon A 3. The intersection of half the interlimb angle and the horizon is the hinge. ⁾ ∥ ⁾ ∥

5. N 8009001000110012001300140015001600 600 800 1000 1200 400 200 0 TWT (msec) CMP 2 km Line name: SSR-1 ✂ Cut here to 600msec 0 600 800 1000 1200 400 200 Note the CMP position and TWT of the hinge Hinge for horizon A CMP position of hinge TWT of hinge

6. N 8009001000110012001300140015001600 600 800 1000 1200 400 200 0 TWT (msec) CMP 2 km Line name: SSR-1 ✂ Cut here to 600msec 0 600 800 1000 1200 400 200 Find the axial plane and note the CMP position at 0msec TWT The axial plane divides the layer symmetrically and intersects the hinge. Axial plane for horizon A CMP position of axial plane

7. 600 800 1000 1200 400 200 0 600 800 1000 1200 400 200 0 14001300120011001150125013501050 SE 2 km TWT (msec) CMP ✂ Cut here to 600msec Line name: SSR-2 Again find the position of the hinge 1. Trace the line of each limb to see where they meet. 2. Measure the interlimb angle and mark the centre point. ⁾ ∥ ⁾ ∥ Hinge for horizon A 3. The intersection of half the interlimb angle and the horizon is the hinge.

8. 600 800 1000 1200 400 200 0 600 800 1000 1200 400 200 0 14001300120011001150125013501050 SE 2 km TWT (msec) CMP ✂ Cut here to 600msec Line name: SSR-2 Hinge for horizon A Note the CMP position and TWT of the hinge CMP position of hinge TWT of hinge

9. 600 800 1000 1200 400 200 0 600 800 1000 1200 400 200 0 14001300120011001150125013501050 SE 2 km TWT (msec) CMP ✂ Cut here to 600msec Line name: SSR-2 Hinge for horizon A Finally add the axial plane and note the CMP position at 0msec TWT Axial plane for horizon A CMP position of axial plane

10. Steps 5-6

11. Plot the position of the fold axial plane for each seismic profile on the map Indoor mapping Basemap showing location of seismic profiles (basemap surface equivalent to 0ms TWT) 2 km SSR-2 SSR-1 × Position of axial plane for horizon A × Note: The map surface is equivalent to 0msec TWT

12. Indoor mapping Basemap showing location of seismic profiles (basemap surface equivalent to 0ms TWT) 2 km SSR-2 SSR-1 × Position of axial plane for horizon A × Note: The map surface is equivalent to 0msec TWT Join the two points together to give the fold axial trace Fold axial trace

13. Steps 7-10

14. Plot the position of the hinge for each seismic profile on the map Indoor mapping Basemap showing location of seismic profiles (basemap surface equivalent to 0ms TWT) 2 km SSR-2 SSR-1 Position of hinge for horizon A Position of hinge for horizon A

15. Indoor mapping Basemap showing location of seismic profiles (basemap surface equivalent to 0ms TWT) 2 km SSR-2 SSR-1 Overlay the TWT panel on the map to line up with the hinge positions

16. Indoor mapping Basemap showing location of seismic profiles (basemap surface equivalent to 0ms TWT) 2 km SSR-2 SSR-1 Mark the intersection with SSR-1 and SSR-2 SSR-1 SSR-2

17. SSR-1 SSR-2 × × SE Plot the TWT of the hinge on the panel

18. SSR-1 SSR-2 × × SE Plunge measured as the angle from horizontal Horizontal ⁽ Join the two points together, this will give the plunge