D’Alembert’s solution

From SEG Wiki
Revision as of 13:25, 22 April 2021 by Covarj (talk | contribs)
Jump to: navigation, search
Other languages:
English • ‎español
Problems in Exploration Seismology and their Solutions
Series Geophysical References Series
Title Problems in Exploration Seismology and their Solutions
Author Enders A. Robinson and Sven Treitel
Chapter 1
DOI http://dx.doi.org/10.1190/1.9781560801610
ISBN 9781560801481
Store SEG Online Store

Jean-le-Rond d’Alembert was born in Paris on 16 November 1717, and died there on 29 October 1783. He enunciated the principle known by his name (d’Alembert, 1743[1]). D’Alembert’s principle allows the reduction of a dynamic problem into a static problem. This feat is accomplished by introducing a fictitious force equal in magnitude to the product of the mass of the body and its acceleration but in a direction opposite to the direction of acceleration. The result can be inferred from Newton’s third law of motion, the full consequences of which had not been realized previously. This principle enabled mathematicians to obtain the differential equations of motion for any rigid’tem.

Figure 2.  Illustration of spherical wavefronts and radial raypaths from a point source in a uniform medium.

Geophysicists remember d’Alembert as the one who first found and solved the wave equation (Robinson and Clark, 1987b[2]). The 1D wave equation is


where v is a constant. He was able to show that


is the general solution of the 1D wave equation, where and are arbitrary functions. This solution is known as the d’Alembert formula. The letter f is the standard notation for a mathematical function, and this usage will always be so. However, we already have used the letter f for the frequency, and that can lead to confusion. An alternative would be to denote frequency by the Greek letter v (lowercase nu), which is done in Sheriff’s Encyclopedic Dictionary of Applied Geophysics (Sheriff, 2002[3]). However, the Greek nu looks too much like the letter v, which is used for velocity. Because the meaning should be clear from the context, in this book we will use the letter f both as a symbol for a mathematical function and as a symbol to denote frequency. A rose is a rose is a rose. In other words, things are what they are.


  1. d’Alembert, J., 1743, Trait’ de Dynamique: Paris.
  2. Robinson, E. A., and R. D. Clark, 1987b, The wave equation: The Leading Edge, 6, no. 7, 14-17.
  3. Sheriff, R. E., 2002, Encyclopedic dictionary of applied geophysics, 4th ed: SEG Geophysical Reference Series No. 13.

Continue reading

Previous section Next section
Wavefronts and raypaths One-dimensional waves
Previous chapter Next chapter
none Digital Imaging

Table of Contents (book)

Also in this chapter

External links

find literature about
D’Alembert’s solution
SEG button search.png Datapages button.png GeoScienceWorld button.png OnePetro button.png Schlumberger button.png Google button.png AGI button.png