OCR A-Level Geography Geographical debates (03), June 2025: Question 5

✅ Acceptable Limitations (Any 3 for 3 marks)

• Model oversimplification: It portrays recovery as a smooth, continuous curve rather than a complex, fractured reality.
• Lack of quantitative metrics: The vertical axis ("Quality of life") lacks objective numerical measurement or standard indicators.
• No spatial/regional context: Does not specify geographical location, wealth levels, or governance structures unless curves A, B, and C are explicitly labelled.
• Neglects hazard-specific characteristics: Does not reflect event type, intensity, duration, or recurring secondary hazards (e.g. aftershocks, liquefaction).
• Generalised time frames: The horizontal time scale is vague (e.g. "hours to days to years") and does not capture variable recovery rates.
• Omits pre-disaster mitigation: Fails to clearly illustrate existing preparedness, early evacuation, or hazard modification prior to the event.

🧠 Exam Technique & Mark Scheme Guidance

• 3 separate points required: Examiners mark this as 3 × 1 (SEEN) . Make three concise, distinct statements rather than one long rambling paragraph.
• Focus on the relationship: Ensure limitations link specifically to disaster and response (e.g. why the model does not show differences between LEDCs and MEDCs, or why it cannot account for multiple compounding hazard events).
• Direct critique: Start sentences directly: "The model lacks quantitative data for..." or "It assumes a single isolated event without showing...".

❌ Common Errors to Avoid

• Describing rather than evaluating: Simply reciting what the curve shows (e.g. "quality of life drops and then rises") scores zero marks.
• Vague complaints: Stating "it is too small" or "it is confusing" is not credited as a geographical limitation.
• Repeating the same point: Stating "no numbers on the axis" and "no data for quality of life" are marked as a single credited point.

💡 Key Knowledge: The Park Model (1991)

The Park Model illustrates how quality of life changes through three stages: Pre-disaster, Relief & Rehabilitation (hours to weeks), and Reconstruction (weeks to years). Recovery may return to normal, improve (mitigation/build back better), or worsen depending on resilience and adaptive capacity.

💡 Core Scales Breakdown

Candidates can achieve Level 3 (5–6 marks) by fully explaining at least two scales in depth, though discussing all three provides the most robust answer:

• Richter Scale (ML): Developed in 1935 by Charles Richter. An open-ended logarithmic scale measuring the maximum wave amplitude recorded by a seismograph. Each unit increase represents a 10× increase in wave amplitude and an approximately 30- to 32-fold increase in energy released. Designed primarily for local shallow earthquakes within 600 km.
• Moment Magnitude Scale (Mw): The standard modern scale for seismologists. Calculates total seismic energy based on physical geological parameters:
  M₀ = μ × D × A (where μ = rock shear modulus/rigidity, D = average slip displacement along the fault, and A = area of fault rupture). It is logarithmic, has no upper limit, and accurately measures large-magnitude earthquakes (> 8.0) where the Richter scale suffers from saturation.
• Modified Mercalli Intensity Scale (MMI): Measures the observable effects and severity of ground shaking (intensity) rather than pure physical energy. It uses qualitative descriptions ranked from I (imperceptible) to XII (total destruction). Depends heavily on distance from epicentre, local geology (e.g. liquefaction), building codes, and population density.

📐 Mathematical & Conceptual Mechanics

Logarithmic Scale Mechanics:

• Amplitude: Magnitude 6 is 10¹ = 10× larger amplitude than Magnitude 5.
  Magnitude 7 is 10² = 100× larger amplitude than Magnitude 5.
• Energy Release: The energy formula scales by 10^(1.5 × ΔM) ≈ 31.6-fold per unit.
  A jump of 2 units (e.g., Mw 6.0 to 8.0) releases ~1000× more energy (31.6 × 31.6 ≈ 1000).

🧠 Level Descriptors & Reaching Level 3 (5–6 Marks)

• Level 3 (5–6 marks): Demonstrates thorough understanding with well-developed comparative ideas. Explicitly explains how scales function (e.g. logarithmic properties, physical fault variables) and evaluates pros and cons.
• Level 2 (3–4 marks): Demonstrates reasonable understanding with developed points (e.g. describes two scales and mentions that Richter is 1 to 10 or logarithmic, but lacks technical precision).
• Level 1 (1–2 marks): Basic descriptions (e.g. "Richter measures strength, Mercalli measures damage").

❌ Common Misconceptions & Pitfalls

• Confusing Magnitude with Intensity: Magnitude is an intrinsic physical property of the earthquake (one value per quake). Intensity (Mercalli) varies across space depending on local ground conditions, depth, and building types. (Note: Mark schemes accept Mercalli when asked about magnitude scales if contextualised as a measure of earthquake size/impact).
• Assuming the Richter Scale has an upper limit of 10: The Richter scale is theoretically open-ended, though it saturates for large earthquakes (above ~M7–8), which is why the Moment Magnitude Scale is preferred today.
• Mixing up amplitude vs energy: Many students write that each whole number on the Richter scale is "10 times more energy" instead of 10 times greater wave amplitude and ~30–32 times more energy.