Target |
Best technique | Worst technique |
Mine tunnel |
gravity | magnetics |
Buried 65 gallon steel drums |
Resistivity, GPR, magnetics | Gravity, refraction |
Lead-lined coffin |
GPR, EM-31, magnetics | gravity |
Mafic igneous dike under sediment |
magnetics | GPR, resistivity, EM31 |
Thickness of unconsolodated sediments over bedrock |
Refraction, resistivity | EM-31, (GPR), magnetics |
2. no north arrow, no scale, ends of profile ambiguous, no absolute location, geophone ids missing
3. (1) Drift correct, (2) Convert from counter units to mGal, (3) latitude correction, (4) elevation (free-air) correction, (5) Bouguer correction. (6)Terrain correction
4. A. Yes, there are alternatives--increase the thickness and resistvity of layer 2
B. Yes; increase layer 2 thickness to 7 m and resistivity to 50 ohm-m
5. Layers are 200, 50, 1000 ohm-m; thickness on left is 1 m/19 m, on right 10 m/10 m, decline in EM 31 resistivities (higher conductivities) indicates that layer one thins between 2 profiles
6.
7.
8. Reciprocity is violated; the apparent velocities of the top layer differ on forward and reversed by a lot, the crossover distance is greater for the reversed than forward shot but the apparent velocity of the second layer is lower for the reversed profile.
9. Resistivity sounding to get water table, perhaps with EM31 for variation of table. Drums to be located by magnetics, which will both see drums very well and give depth information. GPR is also a possibility here.
GEOL4714/5715 home | C. H. Jones | CIRES | Dept. of Geological Sciences | Univ. of Colorado at Boulder
Last modified at Tuesday, October 25, 2005 4:02 PM
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