Quiz 1 Notes

Today's topics

• Mechanisms of earthquakes.
  • Plate tectonics.
  • Fault motions and elastic rebound theory.

• Seismic hazards
  • Fault rupture
  • Ground failure
    • Liquefaction
    • Land slides
  • Ground shaking
  • Tsunamis

• Measuring earthquakes and their effects
  • Intensity: Modified Mercalli Scale
  • Magnitude: Richter Scale

• Assessing hazards at a particular site
  • Risk and return period
  • Seismic risk maps

EERC

The Causes and Effects of Earthquakes

Plate Tectonics and Faults

[Bolt 78, p. 14]

A model of underground shocks associated with the 1994 Northridge earthquake in Los Angeles (from the Southern California Earthquake Center).

[SCEC 1996, /animation.html]

Seismic hazards

Fault Rupture

Ground Shaking

A structure which straddles a fault rupture will almost surely be destroyed, but that probablity is very low.

The ground shaking induced by fault rupture causes much more widespread damage.

The nature of shaking at a particular site depends on many factors concerning the nature and distance of the origin of the earthquake and the surrounding geology.

[Bolt 78, p. 32]

Waves propogate through the earth's crusts in several forms. P waves and S waves are most prominent.

[Bolt 78, p. 29]

Tsunami

In addition to fault rupture and ground shaking, shaking can also induce tidal waves, called tsunamis. (from the Cornell Theory Center)

[CTC 1996, /~devine/tsunami.html]

Liquefaction

Landslide