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

 

77) Consider a hypothetical zero-offset seismic acquired over a reflector whose dip is 30⁰. The velocity of the medium above the reflector is 2 km/sec and the trace spacing is 25 m. The maximum unaliased frequency in the data is _____Hz

 

 (Thanks to Chandrasekhar, ANU)

 

Solution:

 Given that the velocity of the medium = 2 km/sec

                                                               = 2000 m/sec

 Dip of the reflector (θ) =30⁰

Trace spacing = 25 m

Unaliased frequency (f_max) =?

 

We know that $ trace spacing = \frac{V}{4\times f_{max}\times \sin\theta}$

 

$f_{max}=\frac{V}{4\times trace spacing\times \sin\theta}$

 

$f_{max}=\frac{2000}{4\times 25\times \sin30}$

 

$f_{max}=\frac{2000}{4\times 25\times 0.5}$

 

$f_{max}=\frac{2000}{50}$

 

$f_{max}=40 Hz$