Elastic moduli

• Young’s modulus, E– Shortening || stress

• Bulk modulus, k – Volume change / pressure

• Shear modulus, – Rotation plane stress

• Poisson’s ratio, – Ratio perp/parallel strains

11=E(L/L)

L

• Young’s modulus, E– Shortening || stress

• Bulk modulus, k – Volume change / pressure

• Shear modulus, – Rotation plane stress

• Poisson’s ratio, – Ratio perp/parallel strains

Elastic moduli

K=-V dP/dV

= dP/d

• Young’s modulus, E– Shortening || stress

• Bulk modulus, k – Volume change / pressure

• Shear modulus, – Rotation plane stress

• Poisson’s ratio, – Ratio perp/parallel strains

Elastic moduli

= xy/xy/2

• Young’s modulus, E– Shortening || stress

• Bulk modulus, k – Volume change / pressure

• Shear modulus, – Rotation plane stress

• Poisson’s ratio, – Ratio perp/parallel strains

=-22/ 11

Elastic moduli

QuickTime™ and a decompressor

are needed to see this picture.

• Young’s modulus, E– Shortening || stress

• Bulk modulus, k – Volume change / pressure

• Shear modulus, – Rotation plane stress

• Poisson’s ratio, – Ratio perp/parallel strains

Elastic moduli

QuickTime™ and a decompressor

are needed to see this picture.

Auxetic material

=-22/ 11

Richard Oldham

Discovery of the Earth’s (outer) core (1906)

Richard Oldham

Discovery of the Earth’s (outer) core (1906)

Andrija Mohorovicic

Discovery of the MOHO discontinuity (1909 or 1910?)

Beno Gutenberg

Accurate measure of the core-mantle boundary--or “Gutenberg discontinuity”--

radius (1912)

Harold Jeffreys

The core is fluid (1926)

Inge Lehmann

Discovery of the Earth’s inner core (1936)

Inge Lehmann

Discovery of the Earth’s inner core (1936)

P-wave paths S-waves

“Travel time” of seismic phases vs. epicentral distance(Jeffreys-Bullen)

Don AndersonAdam Dziewonski

Preliminary Reference Earth Model (1981)

Preliminary Reference Earth Model (1981)

PREM radially symmetric earth model

Best fit to following data:• P and S wave travel times versus

• Body wave evidence for boundaries• crust-mantle• transition zone (410 km, 660 km jumps)• core-mantle boundary• outer-inner core boundary

• Surface wave phase velocities as a function of wave period• Rayleigh waves (SV and P)• Love waves (SH)

• Periods of free oscillations• Spheroidal (Standing Rayleigh waves + gravity)• Torsional (Standing Love waves)

Fowler, page 106

Phases: freq dec. as distance inc.

Groups: constant frequency/period

# great circles = l-1

Zerocrossings

Varies w/ depth, too!Diff. modes sensedifferent depths.

“Sensitivity kernel”