REVIEW OUTLINE:  STRESS, STRAIN, AND EARTHQUAKE GENERATION

Stress: Force per unit area

• Units: Pascal (= Newtons/sq. meter), PSI (lbs/sq. in.)
• Compression
• Tension
• Shear

Strain:  Deformation of solid material in response to stress

• Compression, tension, shear
• Recoverable
• Permanent (non-recoverable)

Elastic Materials

1. Linear (proportional) relation between stress & strain
2. Recoverable strain (when stress is removed)
3. Brittle failure (yield point)

Plastic Materials

1.   Non-linear relation between stress & strain

2. Non-recoverable strain
3. No yield point (plastic flow)

Elastic Rebound Theory

1. Slow period of strain accumulation
2. Accumulation of stress at fault
3. Stress exceeds strength of fault à sudden rupture of fault
4. Release of elastic strain energy:  earthquake!
5. Cycle starts over again