EARTHQUAKES (ALL TOPICS)

CAUSES OF AN EARTHQUAKE? - LINK TO PLATE BOUNDARIES

Most earthquakes happen along plate boundaries because that’s where the most stress builds up from plate movement.

  1. convection currents are sent through the mantle

  2. plates lock

  3. energy is released

  4. plates move apart

MEASURING EARTHQUAKES…

Earthquakes are measured using seismometers, which record ground vibrations as seismograms. The strength of an earthquake is measured using the Moment Magnitude Scale (or the Richter Scale), which shows the energy released. The effects and damage are measured using the Mercalli Intensity Scale.

EARTHQUAKE HAZARDS…

Earthquake hazards are the dangerous effects caused by earthquakes.

Primary hazards include ground shaking and buildings collapsing. Secondary hazards include fires, landslides, and tsunamis.

Strong shaking can damage roads, bridges, and buildings. Underwater earthquakes can cause large waves called tsunamis, such as those in the Pacific Ring of Fire. Earthquakes can also trigger landslides and fires from broken gas lines.

WHAT FACTORS CAN INCREASE THE DAMAGE CAUSED BY AN EARTHQUAKE?

Several factors can increase the level of damage caused by an earthquake:

  • Magnitude – stronger earthquakes release more energy, causing greater destruction.

  • Distance from the epicentre – places closer to the epicentre experience more intense shaking.

  • Depth of the focus – shallow earthquakes tend to cause more damage than deep ones.

  • Population density – more people and buildings = higher potential damage.

  • Building quality – poorly built structures are more likely to collapse.

  • Level of preparedness – countries with better planning, drills, and emergency services suffer less damage.

  • Secondary hazards – effects like landslides, fires, or tsunamis can worsen the impact.

Key idea: Damage is not just about the earthquake itself, but also how vulnerable people and buildings are.

MANAGEMENT AND PREPAREDNESS FOR AN EARTHQUAKE (E.G. BEFORE,DURING AND AFTER) MAKE SURE TO LOOK AT ASEMIC BUILDINGS TOO

Before:

  • Build earthquake-resistant (aseismic) buildings using flexible materials and base isolation

  • Retrofit older buildings

  • Emergency planning, education, and drills

During:

  • Drop, cover, and hold on

  • Stay away from windows / move to open space if outside

After:

  • Search and rescue

  • Provide aid (food, water, shelter)

  • Rebuild with safer designs

WHY THEY’RE DEADLY + IMPACTS

Why earthquakes are deadly

  • Sudden with little warning

  • Buildings collapse, trapping people

  • High population density in cities

  • Secondary hazards increase danger

Impacts:

  • Deaths and injuries

  • Homelessness

  • Damage to infrastructure (roads, water, electricity)

  • Economic losses and slow recovery