🌏 Lesson 11: Earthquake Hazards and Their Characteristics 

1️⃣ What Are Earthquake Hazards?

An earthquake hazard is any dangerous event or condition caused by earthquakes that can harm people, property, livelihood, or the environment.

📌 Earthquake hazards may happen:

• during shaking

• right after shaking

• minutes to hours later (like tsunami or landslides)

2️⃣ Types of Earthquake Hazards (with Characteristics)

✅ A. Ground Shaking

What it is:
The vibration or movement of the ground during an earthquake.

Why it’s dangerous:

• causes buildings to sway or collapse

• can throw people off balance

• damages bridges, roads, and utilities
  
  

Areas most prone:

• everywhere near the fault

• soft ground shakes stronger than hard rock
  
  

Typical effects:
collapsed buildings, falling objects, injuries, broken lines.

✅ B. Ground Rupture

What it is:
A visible crack or break on Earth’s surface when a fault moves.

Why it’s dangerous:

• splits roads and buildings in half

• destroys foundations instantly

• permanent ground displacement
  
  

Areas most prone:

• directly on or near a fault line
  
  

Typical effects:
offset pavements, torn pipelines, collapsed structures along faults.

✅ C. Liquefaction

What it is:
When water-saturated soil becomes soft like liquid during shaking.

Why it’s dangerous:

• buildings sink or tilt

• roads buckle

• ground loses strength
  
  

Areas most prone:

• coastal areas

• river plains

• reclaimed land

• places with loose sandy soil + high groundwater
  
  

Typical effects:
tilted buildings, cracked ground, sand boils.

✅ D. Earthquake-Induced Landslide

What it is:
Shaking causes rocks and soil to slide downhill.

Why it’s dangerous:

• buries houses or roads

• blocks rivers leading to flash floods

• isolates communities
  
  

Areas most prone:

• steep slopes

• deforested mountains

• areas with loose soil
  
  

Typical effects:
collapsed hillsides, blocked highways, buried homes.

✅ E. Earthquake-Induced Ground Subsidence

What it is:
A sudden lowering or sinking of the ground after shaking.

Why it’s dangerous:

• damages buildings and roads

• increases flooding risk in lowlands

• creates uneven ground
  
  

Areas most prone:

• soft clay-rich soils

• coastal plains

• areas with over-extracted groundwater
  
  

Typical effects:
sunken roads, cracked foundations, water pooling.

✅ F. Lateral Spreading

What it is:
A ground movement where soil shifts sideways during shaking (often near bodies of water).

Why it’s dangerous:

• drags roads and buildings sideways

• breaks bridges, pipelines

• happens fast and unpredictably
  
  

Areas most prone:

• riverbanks

• coastal areas

• loose sandy soils
  
  

Typical effects:
sideways cracks, tilted posts, shifted houses.

✅ G. Tsunami

What it is:
A series of large ocean waves caused by underwater earthquakes.

Why it’s dangerous:

• floods coastal communities quickly

• sweeps away houses, people, vehicles

• may arrive minutes after shaking
  
  

Areas most prone:

• coastal areas near trenches/faults

• low-lying shorelines
  
  

Warning signs:

• strong earthquake near coast

• sudden sea level retreat

• loud roaring sound
  
  

Typical effects:
coastal flooding, drowning, massive debris damage.

4️⃣ Safety Measures to Reduce Earthquake Risk

✅ BEFORE an earthquake:

• secure heavy shelves and appliances

• identify safe spots (under sturdy table, near inner wall)

• prepare a Go Bag

• know evacuation routes

• family emergency plan + drill
  
  

✅ DURING an earthquake:

• Duck, Cover, Hold

• stay away from windows and falling objects

• do not run outside while shaking

• if outdoors, go to open area

• if near coast, prepare to evacuate after shaking stops
  
  

✅ AFTER an earthquake:

• check injuries first

• inspect for gas leaks / fire hazards

• evacuate damaged buildings

• expect aftershocks

• listen to official advisories

🧠 Summary / Takeaways

• Earthquakes cause multiple hazards, not just ground shaking.

• Major hazards include:
  ✅ shaking, rupture, liquefaction, landslide, subsidence, lateral spreading, tsunami

• Risk depends on location and ground type.

• Preparedness and safety actions reduce harm.