You are here:

Geophysics/Geophysics-Amplitude spectrum


Hello sir ,
         Kindly clarify the following questions for which I am not able to get clear answers.
1)Is power spectrum and amplitude spectrum ,both mean the same?If so then is it different from phase spectrum?
2)when computing the frequency of a seismic trace ,does FFT utilizes the amplitude value at every sample for computing?
3)For an amplitude spectrum of a seismic trace can the amplitude value be zero multiple times for different frequencies?
3)why dont we get any negative values in Amplitude spectrum graph though the amplitudes values are both negative and positve<
Kindly find time to answer these questions
Thanking you

Dear Jeevan,

I hope the following concise answers explain your questions:

1) Power spectrum defines the power of a signal amplitude at frequencies whilst the amplitude spectrum defines signal amplitude at frequencies without taking its power. Amplitude & Power spectra are different from Phase spectrum as Y-axis is amplitude instead of phase.

2) FFT is a windows based transformation with a central sample. It is a sliding window that operates on an each window.

3) True

4) This is very basic. Plz check the FFT equation and note that the amplitude is a coefficient in frequency domain whilst the sign is a phase that comes from sine / cosine function.



All Answers

Ask Experts


Farrukh Qayyum


I would like to answer Geophysical questions with keen interest, specifically exploration related. I want to hear from users for their queries on exploration geophysics/geology. Especially in the discipline of Reservoir Characterization from seismic reflection data. The questions related to basics and interpretational applications would be most welcome. I can also answer queries related to sequence and/or seismic stratigraphy, geology, general geomorphology, seismic geomorphology and other relevant questions. I can not answer the questions related to gravity, magnetic, or resistivity surveying or question related to the fluid dynamics. Such categories are not related to my experience.


Over eight years in different services with additional case studies of Pakistan, China, Saudi Arabia, North Sea, Africa and Netherlands offshore.

dGB Earth Sciences, The Netherlands.


4D Wheeler Diagrams: Concept and Applications, Qayyum, F., P. de Groot, N. Hemstra, and O. Catuneanu, 2014, Geological Society, London, Special Publications, v. 404, p. SP404.1, doi:10.1144/SP404.1.

A Modern Approach to Build 3D Sequence Stratigraphic Framework Qayyum, F., Hemstra, N., and Singh, R., 2013, Oil and Gas Journal, vol.111, issue 10.

Dense sets of seismic horizons - A New Approach to Stratigraphic Interpretation Qayyum, F., Hemstra, N., and de Groot, P., 2013, Geophysical Corner, AAPG Explorer, September Issue, 68-69.

Developments and Future Trends in Wheeler Diagrams Qayyum, F., Catuneanu, O., de Groot, P., 2013, 75th EAGE Conference & Exhibition incorporating SPE EUROPEC, London, UK, June 2013.

HorizonCube and Wheeler Transform Generated, Stratal Packages Identified and Correlated on 7 Regional 2D Seismic Lines McDonough, K.J., Qayyum, F., Bouanga, E., and Pierard, C., Horn, B., Gross, J., Danforth, A., Sterne, E.J., Granath, J., AAPG Annual Convention & Exhibition, May 2013

On the horizon, de Groot, P., Qayyum, F., Oilfield Technology, January 2013.

Attributes play important role in seismic interpretation, de Groot, P., Qayyum, F., Hart's E&P Magazine, p. 31-34, October 2012.

From 2D to 4D Wheeler Diagrams, F. Qayyum, P. de Groot, and N. Hemstra, William Smith Meeting 2012, London.

Building a Sequence Stratigraphic Framework from HorizonCube and Well Data F. Qayyum, P. de Groot, J. Yasin 74th EAGE Conference & Exhibition, 2012

An old favourite, F. Qayyum and P. de Groot, Oilfield Technology, March 2012.

Using 3D Wheeler diagrams in seismic interpretation the HorizonCube method F. Qayyum, P. de Groot,N. Hemstra First Break 30 (3), 103-109,2012

Master in Philosophy with specialization in reservoir characterization by using Sequence Stratigraphy. And master in Geophysics with a case study of Punjab Platform.

Awards and Honors
Position Holder in Academics.

©2016 All rights reserved.