Earthquake Notes

From Science Olympiad Student Center Event Wiki

This topic has to do with the Dynamic Planet event.

Contents 1 What is an earthquake? 2 Seismographs 3 Types of Seismic Waves 4 Hazards

What is an earthquake?

• a vibration of the earth produced by rapid release of energy.
• energy radiates out from focus
• focus is where the rock breaks creating an earthquake
• energy moves outward from focus in seismic waves

what causes the rock to break? stress-a force or pressure acting on a rock Types of stress

1. compression
2. tensional
3. shear

Strain-the result of stress of deformation

• elastic deformation-when stresses are removed,rock returns to original shape
• plastic deformation-permanent deformation. when stress is removed rocks stay bent
• rupture-breakage and fracturing of the rock causing an earthquake.

brittle materials break during elastic deformation

Seismographs

• A fault is a break or crack in the rock along which movement has occurred.
• movement along the fault produces earthquakes and seismic waves.
• a seismograph detects seismic waves.
• first seismograph developed by the Chinese about2000 years ago.
• basic components
  • suspended mass that is attached to and moves with the ground
  • movement is recorded on a rotating drum or magnetic tape

Types of Seismic Waves

1. body waves

• P-waves
  • primary
  • fastest
  • travels though solids and liquids
• S-waves
  • secondary shaking side to side
  • solids only
• surface waves
  • referred to as l-waves
  • complex motion up-down and side to side
  • slowest
  • damage to structures

Hazards

1. Ground motion-shaking of the ground, depends on

• local geological positions such as loose unconsolidated sediment which is worst
• Size
  • distance from epicenter farther away the less damage
• Construction
  • concrete are brittle and will damage more easily
  • wood and steel less susceptible to damage

1. Faulting and Ground Rupture-occurs along the fault zone that moves during an earthquake
2. After Shocks- dangerous because they can further collapse structures that are damages
3. Fire- started by power lines,gas lines rupturing. more dangerous in the water lines break
4. Landslides-quakes may trigger landslides
5. Liquefaction- turning the ground into a substance similar to a liquid which will make structures sink
6. Changes in ground level
7. Tsunamis-giant ocean waves
8. flooding-may be due to rupture of dams and levees