How Do Earthquakes Happen?
Earthquakes are caused by the sudden release of energy in Earth's crust, usually when tectonic plates move past each other.
The Cause: Plate Tectonics
Earth's crust is broken into ~15 major plates floating on hot, flowing mantle rock. These plates move 1-10 centimeters per year.
- Convergent: Plates collide
- Divergent: Plates pull apart
- Transform: Plates slide past each other
The Mechanism: Stress and Slip
Plates don't slide smoothly. Friction locks them together. Stress builds for years, decades, centuries.
When stress exceeds friction — snap. The plates suddenly slip, releasing energy as seismic waves.
Focus (hypocenter): Where the slip begins underground.
Epicenter: Point on the surface directly above the focus.
Seismic Waves
- P-waves (primary): Compression waves, fastest, felt first
- S-waves (secondary): Shear waves, slower, cause most shaking
- Cause most damage
- Roll like ocean waves
Measuring Earthquakes
Richter Scale (outdated for large quakes): Measures amplitude of seismic waves.
Moment Magnitude Scale: Measures total energy released. Each whole number = 32× more energy.
- Magnitude 5: Light damage
- Magnitude 6: Moderate damage
- Magnitude 7: Major damage
- Magnitude 8+: Catastrophic (Great earthquakes)
Can We Predict Earthquakes?
Not yet. We can identify high-risk zones and estimate long-term probability, but precise prediction remains impossible.
Early warning systems give seconds to minutes of notice once an earthquake starts.
Related Reading
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