Seismic Hazards

Question 1

What causes earthquakes? (Mention 3 things)

Answer 1

• Earthquakes occur due to stress release along faults caused by plate movements.
• The focus is the point underground where the earthquake starts.
• The epicentre is the point directly above the focus on the surface.

Question 2

What are the 2 different types of seismic waves?

Answer 2

• Primary (P) waves: Fastest, compressional waves that move through solids and liquids.
• Secondary (S) waves: Slower, only move through solids, cause more damage. Surface waves: Move along Earth’s surface, most destructive.

Question 3

What are the 3 different types of faults that cause earthquakes?

Answer 3

• Normal faults: Occur at divergent boundaries, crust pulls apart.
• Reverse (thrust) faults: Occur at convergent boundaries, crust is compressed.
• Strike-slip faults: Occur at transform boundaries, plates slide past each other.

Question 4

What are the 2 primary hazards of earthquakes?

Answer 4

• Ground shaking: Causes buildings to collapse.
• Surface rupture: Cracks and displacement of land along faults.

Question 5

What are the 3 secondary hazards of earthquakes?

Answer 5

• Liquefaction: Saturated ground behaves like a liquid, causing buildings to sink.
• Landslides: Triggered by ground movement on steep slopes.
• Tsunamis: Caused by undersea earthquakes displacing water.

Question 6

How do tsunamis form? (Mention 2 things)

Answer 6

• Underwater earthquakes cause seafloor displacement, pushing water upwards.
• Waves travel fast in deep water and slow in shallow water, increasing height.

Question 7

What are the 3 impacts of tsunamis?

Answer 7

• Widespread coastal flooding.
• Infrastructure destruction (homes, roads, power lines).
• Loss of life due to fast-moving waves.

Question 8

Where do most earthquakes occur? (Mention 2 things)

Answer 8

• Along plate boundaries, particularly in convergent and transform zones.
• The Pacific Ring of Fire is the most seismically active region.

Question 9

Can earthquakes occur away from plate boundaries? (If so give an example)

Answer 9

Yes, intraplate earthquakes happen due to ancient fault lines and mantle hotspots (e.g., New Madrid Seismic Zone, USA).

Question 10

When and where did the Gorkha earthquake occur? (Mention 2 things)

Answer 10

• 25 April 2015, magnitude 7.8.
• Epicentre near Kathmandu, Nepal.

Question 11

What were the 3 primary impacts of the Gorkha earthquake?

Answer 11

• 9,000 deaths, 22,000 injuries.
• 600,000 buildings destroyed.
• Landslides and avalanches blocked roads and buried villages.

Question 12

What were the 3 secondary impacts of the Gorkha earthquake?

Answer 12

• Tourism decline (Everest climbing season cancelled).
• Food and water shortages due to damaged infrastructure.
• Aftershocks continued to cause damage.

Question 13

What were the 3 immediate responses to the Gorkha earthquake?

Answer 13

• Search and rescue operations by Nepalese army.
• International aid sent (e.g., India and China provided relief supplies).
• Tents and temporary shelters set up for displaced people.

Question 14

What were the 3 long-term responses to the Gorkha earthquake?

Answer 14

• Stricter building codes to make infrastructure earthquake-resistant.
• Rebuilding efforts with international funding.
• Improved disaster preparedness through early warning systems.

Question 15

How can earthquakes be predicted? (Mention 3 things)

Answer 15

• Seismometers detect small tremors.
• GPS monitoring tracks crustal movements.
• Historical data helps identify high-risk areas.

Question 16

What 3 strategies can reduce earthquake damage?

Answer 16

• Earthquake-resistant buildings (shock absorbers, flexible materials).
• Land-use zoning (keeping critical infrastructure away from fault zones).
• Education and drills (teaching people what to do during an earthquake).