4.1

• 1. Earthquakes occur along Faults http://neic.usgs.gov/neis/qed/

2. Fault

• A fracture, or break, in Earths lithosphere, along which blocks of rock move past each other

3. Rocks bend as stress is put on them.

• Stress - the force exerted when an object presses on, pulls on, or pushes against another object.

• • Some parts of a fault, rock on either side may slide along slowly and constantly

• • Other parts the rocks may stick or lock together, putting stress on them

• • As stress increases, the rocks break free causing an earthquake

4. Earthquake

• Anearthquakeis a shaking of the ground caused by the sudden movement of large blocks of rock along a fault.

5. Most earthquakes occur along plate boundaries

• This is where faults occur.

• The blocks of rock that move during an earthquake are much smaller than the tectonic plates

6. Factors of the Strength of an Earthquake

• how much stress builds up before the rocks move.

• the distance the rocks move along the fault.

7.

• 80% of all earthquakes occur in abeltalong the edges of the Pacific Ocean

8. Fault Classification

• Faults are classified by the way the rocks move

• More than one type of fault may be present along a boundary

9. Normal Faults

• The block of rock above the fault plane slides down relative to the other block

• Earthquakes along normal faults are common near divergent boundaries.

10. Reverse Faults

• The block above the fault plane moves up relative to the other block.

• Occurs along convergent boundaires

11. Strike-Slip Faults

• Blocks of rock move sideways on either side on the of the fault plane.

• • Example: San Andreas fault in California