Earthquake hazards and impacts

Earthquake Hazards and Impacts

What is an Earthquake? 🌍

An earthquake is a sudden release of energy in the Earth's crust that creates seismic waves. Think of it like a giant rubber band that has stretched too far and snaps back, sending ripples through the ground.

How Do Earthquakes Happen? ⚡

Earthquakes occur when stress accumulated along geological faults exceeds the strength of rocks. The stress is released as the rocks slip, producing seismic waves. The amount of energy released is measured by the Richter magnitude:

$M = \log_{10}\left(\frac{A}{A_0}\right)$

Where $A$ is the amplitude of the seismic waves and $A_0$ is a reference amplitude. A difference of 1.0 on the scale means about 32 times more energy released.

Types of Faults and Their Movements

Earthquake Hazards 🚨

• Ground shaking – can topple buildings, cause landslides.
• Surface rupture – fault line breaks the surface, damaging roads and pipelines.
• Liquefaction – saturated soils behave like liquid, undermining foundations.
• Secondary hazards – fires, tsunamis (if undersea), and aftershocks.

Impact on People and Structures 🏗️

- Buildings: Unreinforced masonry collapses; reinforced concrete may crack but often survives.

- Infrastructure: Bridges, tunnels, and pipelines can break, leading to water and gas leaks.

- Human life: Casualties often occur in poorly built homes or during heavy traffic.

- Economic: Repair costs can reach billions of dollars, especially in densely populated areas.

Mitigation and Preparedness 🛠️

1. Building codes: Use base isolation, shear walls, and ductile materials.
2. Public education: “Drop, Cover, and Hold On” drills in schools.
3. Early warning systems: Detect seismic waves and send alerts seconds before shaking.
4. Land‑use planning: Avoid building on fault lines or liquefaction‑prone soils.

Exam Tips for A‑Level Geography