Disaster Management · M2 · papers
Earthquake questions
Solved M2 questions
2-mark and 3-mark practice · full answers below each question
Practice question. Explain the cause of a tectonic earthquake and distinguish focus from epicentre. [3 practice marks]
Answer
Tectonic movement builds stress in rocks locked along a fault. When resistance is overcome, sudden slip releases stored elastic energy as seismic waves. The focus is the point within the Earth where rupture starts; the epicentre is the point on the surface directly above it.
Practice question. Differentiate between interplate and intraplate earthquakes. [2 practice marks]
Answer
Interplate earthquakes occur at boundaries where tectonic plates interact. Intraplate earthquakes occur within a plate, away from its boundary, often on reactivated faults. Both can be damaging; location within a plate does not imply zero seismic risk.
Practice question. Compare P waves and S waves. [3 practice marks]
Answer
| P waves | S waves |
|---|---|
| Faster; arrive first. | Slower; arrive after P. |
| Longitudinal compression and expansion. | Transverse shear motion. |
| Travel through solids and fluids. | Do not travel through liquids as shear waves. |
Practice question. Distinguish earthquake magnitude from earthquake intensity. [3 practice marks]
Answer
Magnitude expresses the size of an earthquake from instrument-based measurements, for example moment magnitude. Intensity expresses its observed effects at a particular site, for example Modified Mercalli I–XII. A given event has an estimated magnitude on a specified scale, but intensities vary among sites because distance, soil and construction differ.
Practice question. Explain soil liquefaction and its effects. [3 practice marks]
Answer
Liquefaction is a loss of strength in susceptible water-saturated loose soil during strong shaking. Rising pore-water pressure reduces contact forces between soil grains, causing the soil to behave temporarily like a fluid. It can cause settlement, tilting of buildings, lateral spreading and damage to buried pipes.
Practice question. Explain three earthquake mitigation measures. [3 practice marks]
Answer
- Safe construction and retrofitting: design and strengthen structures to resist earthquake forces and reduce collapse.
- Non-structural safety: anchor shelves and equipment and protect utilities to reduce falling-object and fire hazards.
- Planning and drills: prepare communication, evacuation and response arrangements so people and agencies act safely.