2.4 Earthquakes

• Meaning and causes of earthquakes
• Terms used: focus, epicentre, seismic waves, magnitude, intensity
• Measurement of earthquakes
• World distribution of earthquake zones
• Effects of earthquakes on the environment
• Disaster preparedness and management strategies

• examine the causes of earthquakes on Earth
• illustrate the distribution of earthquake zones in the world
• investigate the effects of earthquakes on the environment
• design disaster preparedness and management strategies for coping with the effects of earthquakes
• appreciate the understanding of earthquakes for disaster preparedness and management

“Why are earthquakes of concern to humans?”

“Why do two earthquakes of the same magnitude kill very different numbers of people?”

The titles are open to everyone. Reading a lesson needs an account — sign in or create one.

1. What causes an earthquake, and how it is measured
   40 min · 2 practice tasks · quiz
   Why the ground shakes, the words used to describe it, and where earthquakes happen.
2. Effects of earthquakes and how to prepare
   40 min · 2 practice tasks · quiz
   What earthquakes do to land and people, why the same magnitude kills very different numbers, and what can be done.
3. How faults store and release earthquake energy
   40 min · 1 practice tasks · quiz
   Elastic rebound on normal, reverse and strike-slip faults, and why the Kenya Rift produces mostly shallow normal-fault earthquakes.
4. Seismic waves: P, S and surface waves
   40 min · 1 practice tasks · quiz
   How P, S and surface waves travel, why surface waves do most damage, and how the P-S gap gives distance from the epicentre.
5. Locating an epicentre and reading the scales
   40 min · 1 practice tasks · quiz
   Triangulation from three seismograph stations, and how Richter, moment magnitude and Mercalli intensity answer different questions.
6. Why earthquake belts follow plate boundaries
   40 min · 1 practice tasks · quiz
   World earthquake zones explained by convergent, divergent and transform boundaries, and where the East African Rift sits on that map.
7. Earthquakes of the East African Rift in Kenya
   40 min · 1 practice tasks · quiz
   Kenya's live rift: the 1928 Subukia earthquake, other Rift events, and why growing towns on the rift floor change the risk.
8. How earthquakes reshape land, slopes and water
   40 min · 1 practice tasks · quiz
   Scarps, landslides, liquefaction, drainage change and tsunamis, including Rift escarpments, rift-lake sediments and the Kenyan coast.
9. Why Kenyan towns are becoming more vulnerable
   40 min · 1 practice tasks · quiz
   The Rift hazard is not new; Nairobi, Nakuru, Naivasha and informal settlements now put far more people in buildings that can fail.
10. Preparing Kenya for the next Rift earthquake
    40 min · 1 practice tasks · quiz
    Before, during and after: building codes, school drills, family kits, NDOC and Kenya Red Cross, and a plan a Grade 10 class can actually run.