EARTH'S INTERIOR

Behavior of Waves

• reflection
• refraction

Seismic Stratigraphy

Behavior of Seismic Waves

Seismic Wave Velocities

Earth's Interior

• 1909 - Mohorovicic velocity of P-waves increase abruptly at ~50 km
• The Mohorovicic discontinuity (Moho) is the boundary between crust and mantle

The Crust

• Ocean Crust
• 5-12 km thick
• basaltic
• density = 3.0 g/cm3
• Layered

1 sediments

2 pillow basalts

3 sheeted basalt dikes overlying gabbro

The Mantle

• ~2900 km thick
• S-wave velocities vary with depth
• constituents and density vary with depth
• stucture of materials varies with depth (Fig. 10-35)

Structure of the mantle from S-wave velocities

• Fig. 10-35
• LVZ - partially molten
• Olivine structure - peridotite

The Mantle (cont.) 
Seismic Tomography

The Core

• P- and S- wave shadows (Fig. 10-36)

• Outer Core
• ~2300 km thick
• liquid Fe with Ni, S, O, and/or Si
• evidence:
• shadow zone
• magnetic field
• density = 10-12 g/cm3