Geology & Geophysics Applied in Industry Exercise 6b: Calculating Frequency and

Question

Geology & Geophysics Applied in Industry Exercise 6b: Calculating Frequency and Wavelength EXERCISE 6b: Calculating Frequency & Wavelength The objective for this exercise is to estimate the frequency of the seismic data in two windows and to calculate a seismic wavelength. You are given a portion of a scismic line with two enlarged windows. The steps are: 1. estimate the number of cycles over a short time window (e.g, 200 ms). 2. use an cquation to convert from an apparent' to a dominant frequency. 3. calculate the wavelength The seismic data is on page 2. The equations you wil need are Fapparest-ayele/time Interval Velocity/Fdemineat Window 1: 1.2 to 1.3 seconds use a velocity of 2000 m/s # cycles over 0.1 seconds Fappuen® # Cycle / time interval- A Velocity / Fdominant use a velocity of 4000 m/s # cycles over 0.2 seconds- Fapparon: # cycle / time interval

Explanation / Answer

In the present case number of cycle are represented by a pair of black and white reflection in the given time interval of the window.

So,from the first window:

There are 4 pairs of black and white reflections present in the window.

So, the number of cycles=4

Velocity(as given)=2000 m/s

F1(apparent)=#cycles/time interval=4/0.1=40

F2(dominant)=2×F1/=25.464

Wavelength=velocity/F2

=2000/25.464 m=78.54 m

For the second window:

There are 4 pairs of black and white reflections present in the window.

So, the number of cycles=4

Velocity(as given)=4000 m/s

F1(apparent)=#cycles/time interval=4/0.2=20

F2(dominant)=2×F1/=12.732

Wavelength=velocity/F2

=4000/12.732 m=314.16 m

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