Page 67 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

49 (AW/W) dis- material; waves and back because “longitudi- forth, wave wave, back and wave the material For particle horizontal

Elastic Waves strain constants four a for ) of seismic of compressions material the wave “P” called and back sound a is Particle motions for body In a compressional move to the direction Particles of the perpendicular to the direction of propagation of shear — oa horizontally: moving vertical wave sith shear wave with

of transverse the determine velocity series shearing or also are move example 3.8 FIGURE a) particles of the material forth, parallel energy moves. b) wave energy ee = motion; SH motion. particle

of rod ratio between 2v) — to used the a by by or “primary” a material the 3.8a). An waves. move SV =

end the vE v\(1 be describing propagate wave) is earthquakes;.they of (Fig. of
to rod, AW/W v*AL/L contracts. relationship + (1 wave particles . Pr opagation
applied of rod of rod. stretched _ rod width the 2 -—_—= 3 and vcan E parameters waves (compressional compressional from moving is WAVE Direction

modulus area unit length length in a that, for is: (AL/ L) ratio of width which by illustfates to: A= ~ of of the Body A first arrive because waves wave the

Young’s per force original change states strain : Poisson’s original amount (A) according measurements one as of Body Waves material wave). waves direction COMPRESSIONAL

= = = = = = easy used material. the (shear “push-pull”
E L AL ratio v W = constant be of the
F/A longitudinal AW above, then the Types forth compressional and to
where: Poisson's to where: Lame’s cussed Relatively can d through dilatations and nal” parallel a )

very resist the upon rigid and with may Other 3.7). is is

(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