GATE-2018 (24) :Wyllie – Time average equation

 96. The foldage of a 2D common depth point (CDP) reflection profiling conducted using a 72-channel digital recording unit with a geophone interval of 50 m and shot interval of 100 m is

a) 18          b) 36          c) 72          d) 144

(Thanks to Pragnath, AU)

Solution:

Foldage:- A measure of the redundancy of common midpoint per bin in seismic data.

$Foldage=\frac{1}{2}*[Total~receivers~*\frac{Receiver~interval}{Shot~interval}]$

 

Given that $Total~receivers= 72$   $Receiver~interval= 50 m$

$Shot~interval= 100 m$.

 

$Foldage=\frac{1}{2}[72~*\frac{50}{100}]$

 

$Foldage=\frac{1}{2}[72~*\frac{1}{2}]$

 

$Foldage=\frac{1}{2}[36]$

 

$Foldage=18$

 

Therefore, the answer is (a) 18