CSIR-NET JUNE 2018
99) An n-fold 12 channel CDP survey was carried
out with the source spacing (S)equal to the receiver spacing(R).The source
spacing required in units of receiver spacing, to obtain a ‘2n’ foldage is
a)S=0.5R
b)S=0.75R
c)S=R
d)S=2R
(Thanks to Suresh sir ANU)
(Thanks to Neeraja AU)
sol:
Foldage=\frac{1}{2}[number of Geophones
(or)channels\times[\frac{Geophone spacing(or)receiver spacing(R)}{Source
spacing(S)}]]
Foldage=\frac{1}{2}[number of
channels\times[\frac{(R)}{(S)}]]------(1)
n fold\rightarrow12channel
S=R
n=\frac{1}{2}[12\times\frac{R}{S}]
R=S
n=\frac{1}{2}[12\times1]
n=6 ------(2)
2n foldage
2n=\frac{1}{2}[12\times\frac{R}{S}]-(3)
n=6
2\times6=\frac{1}{2}[12\times\frac{R}{S}]
12=\frac{1}{2}[12\times\frac{R}{S}]
24=[12\times\frac{R}{S}]
\frac{1}{24}=\frac{S}{12R}
\frac{S}{R}=\frac{12}{24}
\frac{S}{R}=0.5
S=0.5R
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