1. CH 8 Earthquakes
Produced by the rapid release of elastic energy in rock causing vibrations
Elastic Rebound Theory = the rock springs back into it original place
Occur at faults and plate boundaries

2. Vocab Focus – point within earth where earthquake originates
Epicenter - point on land surface directly above the focus
Aftershocks – follows the main EQ
Foreshocks – EQs that precede the main earthquake
Seismographs – instrument that records EQ waves
Seismograms – the record made by a seismograph

3. Earthquake Waves Primary (P) waves Secondary (S) waves –
Body wave, arrives first, fastest, pass through everything, push/pull wave
Secondary (S) waves –
Body wave, arrives second, slower, pass through solids only, sideways/snake wave
Longitudinal (L) waves –
Surface waves, arrive last, liquefy ground, do most damage, up/down wave

4. Locating an Earthquake
Determined by the difference in arrival times between P and S waves
Know the graph on page 225
Need at least 3 points to determine the location (triangulation)
EQ zones – circum-Pacific belt and oceanic ridge system

5. Measuring Earthquakes
Richter scale
Based on size of largest wave
Scale from
Moment magnitude
More precise
From displacement that occurs along the fault line
Estimates the energy released

6. Earthquake Destruction
Contributing factors
Intensity of eq
Duration of eq
Foundation of building
Structure/materials of building
Damage prevention
Reinforced concrete
Shock absorbers
Counter weights

7. Earthquake Dangers Collapsing structures #1 Fires #2 Landslides
Tsunamis
Move fast: 500–950 km/hr ( mph)
Very long wavelengths
Barely noticeable in open ocean

8. Predicting Earthquakes
Short range prediction are unsuccessful
Long range forecasts are based on the idea that EQs are cyclic.
Land movement
Strain in rocks
Radon gas emissions
Strange animal behavior
Volcanoes
Foreshocks
Seismic gap theory

9. Earth’s Layers
Earth’s interior consists of 3 major zones (chemical composition)
Crust – thin, rocky outer layer
Oceanic and continental
Mantle – most of earth’s volume
Upper and lower mantle
Core – iron/nickel alloy with extreme pressures
Inner (solid) and outer (liquid)

10. Earth’s Interior Lithosphere Asthenosphere Moho Discontinuity
Solid and rigid
The crust and upper mantle
Asthenosphere
Softer and flows
Rest of the mantle
Moho Discontinuity
Boundary that separates the crust from mantle
Shadow zone
Know differences between oceanic and continental crust