Earthquakes: Causes, Regions, and Impacts

Overview

• Earthquakes appear as scars on Earth's surface, with each quake telling a geological story.
• Recorded on all continents, but mainly occur in three key regions:
  • Mid-Atlantic Ridge
  • Alpine Belt
  • Circum-Pacific Belt (80% of all earthquakes occur here)

Causes of Earthquakes

• Result from pressure due to stress in the Earth's crust.
• Stress may be caused by:
  • Volcanic activity
  • Man-made activities
  • Movement of tectonic plates (primary cause):
    • Plates move against, away, along, or beneath each other.
    • Edges of plates may stick, creating pressure until they slip.
    • Sudden release of energy breaks the Earth's crust, causing shockwaves and vibrations.

Earthquake-Prone Regions

• Occur mostly where geologically active plates meet.

Measurement of Earthquakes

• Recorded using seismographs:
  • Oscillate during ground movements.
  • Produce jagged lines; height indicates earthquake severity.
• Measured using the moment magnitude scale:
  • Preferred scale, logarithmic, with no upper limit.
  • Each magnitude level is 10 times greater than the previous.
• Contrast with the Richter scale, which is less used today.

Historical Earthquake: Valdivia, Chile (1960)

• Most powerful recorded earthquake with a magnitude of 9.5.
• Occurred in the Circum-Pacific Belt.
• Triggered a deadly tsunami up to 80 feet high.
• Shockwaves affected the entire planet for days.

Adapting to Earthquakes

• Some regions have developed measures to protect communities:
  • Buildings and bridges designed to sway.
  • Public education on earthquake safety.
  • Government drills for community protection.

Conclusion

• Earthquakes can cause great devastation but are also responsible for creating magnificent geological features.