Page 66 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

49
Elastic Waves
very where: modulus Young’s = E of rod end to applied area unit per force = F/A resist of rod length original = L the of rod. length in change = AL (AW/W) strain of transverse ratio the rod, stretched a that, for states ratio Poisson's upon is: (AL/ L) strain longitudinal to AW/W _ : v*AL/L where: rigid ratio Poisson’s = v and rod of width original W = cont
(k relatively to is stress (A). The acted very ©) p, along It (Fig. that rod before with I. b) The (A) the the shear modulus Young’s
compress to material the applied area is 0) (Al = , and material. directly. y and a of Shear modulus. length AF acts across relative to (L), area (A) rod is subjected resulting length, in length, L). strain the longitudinal

to subjected of a shearing, is of the ~ (Al shearing k the constants k behavior Configuration of material in shear force. Note cube in shear force area A. One side of the cube material. rod of length and cross-sectional to measure Young’s longitudinal stress (force, F, acting (change transverse
easy ability force (/) to constants through calculate sides of area A and displaced a distance Al Opposite side, according to a) A over the cross-sectional area, A).
are when to the length shearing elastic to the FIGURE3.6 change change modulus of the 3.7 used Poisson's ratio. The modulus determines the longitudinal strain AL, divided by the original Poisson's ratio is the (AW/W) divided by (AL/L).
that AV) the to subjected which the is: AF/A Al/l to resistance elastic travel two used describes F/A AL/L a) the FIGURE (W) width can be and toa strain
materials (large refers is over divided by (1) stress resistance no has the waves those and equation: ; Ss

Conversely, in (small of cube by (Al) shear p strong other 0). isotropic fast how to “stretch to a
i volume AP). “rigidity”) material area the modulus _ strain hand, material, body measure measured modulus”) the stress _ strain | “2a

Waves ). » changes stresses (or a divided displacement the shows the (j. = determine however, readily the according Al

Seismic = (k large undergo compressive modulus shear 3.6). When force (AF) shear stress, a such that material on fluid, rigidity lacks unbounded, (p), practical, more be may (or modulus compressed,

Chapter3 incompressible small) small The (Fig. shearing tangential strain the is by For AF. A A =). (uw therefore an For density the be not constants Young's pulled or