The concept of perception of risk

Earthquake & Volcanic Hazards – Perception of Risk (Cambridge AS & A‑Level Geography 9696)

1. Introduction

Perception of risk determines how individuals and communities prepare for, respond to and recover from earthquakes and volcanic eruptions. Understanding the link between the physical nature of the hazards and the social‑psychological factors that shape perception is essential for effective risk management.

2. Geological Background

2.1 Global Distribution of Earthquakes

• Concentrated along plate boundaries: the Pacific “Ring of Fire”, the Alpine‑Himalayan belt, the Mid‑Atlantic Ridge and other sub‑duction zones.
• Intraplate earthquakes occur away from boundaries (e.g., New Madrid, USA) but are generally lower in magnitude.

2.2 Global Distribution of Volcanoes

• Sub‑duction zones: ~75 % of world’s volcanoes (e.g., Andes, Japan).
• Rift zones & divergent boundaries: basaltic shield volcanoes and fissure eruptions (e.g., East African Rift, Iceland).
• Hot‑spots (intra‑plate): volcanic chains formed by mantle plumes (e.g., Hawaiian Islands, Canary Islands).
• Continental volcanic fields: scattered basaltic vents (e.g., Deccan Traps, USA).

2.3 Tectonic Processes & Plate‑Boundary Links

3. Hazard Characteristics

3.1 Earthquake Hazards

• Seismic waves: P‑waves (compressional), S‑waves (shear), Surface waves (Rayleigh & Love) – surface waves cause the greatest damage.
• Magnitude & intensity scales:
  • Richter local magnitude (M_L) – useful for M < 6.
  • Moment magnitude (M_w) – measures total energy released; preferred for large events.
  • Modified Mercalli Intensity (MMI) – describes observed effects on people, structures and the natural environment.
• Primary impacts: Ground shaking, surface rupture.
• Secondary mass‑movement hazards:
  • Liquefaction of water‑logged, loose soils.
  • Land‑slides and rock‑falls on steep slopes.
  • Seismic‑triggered tsunamis (offshore events).
  • Fires caused by broken gas lines or electrical faults.

3.2 Volcanic Hazards

• Eruption styles:
  • Effusive – low‑viscosity basaltic lava flows (e.g., Kīlauea, Hawaii).
  • Explosive – high‑viscosity rhyolitic or andesitic magma producing ash clouds and pyroclastic density currents (e.g., Mount Pinatubo, Philippines).
• Primary hazards: Lava flows, pyroclastic density currents, volcanic gases (SO₂, CO₂, H₂S).
• Secondary hazards: Ash fall (aviation, health, agriculture), lahars (volcanic mudflows), sector collapses, volcanic‑induced tsunamis (e.g., 1883 Krakatoa).

4. Physical & Human Vulnerability

Vulnerability is the degree to which a system is susceptible to damage when exposed to a hazard. It combines physical, social and economic factors.

5. Perception of Risk

5.1 Definition

Perception of risk is the way individuals or communities interpret the probability and severity of a hazard. It is shaped by personal experience, cultural beliefs, media coverage, visibility of past damage and the socio‑economic context.

5.2 Why Perception Matters (AO3)

• Guides preparedness actions such as retro‑fitting, evacuation planning and household emergency kits.
• Influences public support for mitigation policies (building codes, land‑use zoning, early‑warning systems).
• Determines behaviour during an event (stay‑put vs. evacuate, compliance with warnings).

5.3 Factors Influencing Perception of Earthquake & Volcanic Risk

5.4 Comparing Perceived vs. Actual Risk

Risk can be expressed as:

Three common patterns:

1. High perceived – low actual: Over‑estimation leads to anxiety and possibly costly, unnecessary mitigation.
2. Low perceived – high actual: Under‑estimation increases the chance of severe impacts.
3. Aligned perception: When perceived risk matches statistical risk, preparedness is most effective.

6. Scale & Systems Perspective (AO1)

6.1 Spatial & Temporal Scale

• Local scale: Building damage, injuries, immediate evacuation.
• Regional scale: Infrastructure disruption, economic losses, secondary hazards (land‑slides, lahars).
• Global scale: Climate impacts of large eruptions (e.g., Pinatubo’s temporary cooling) and international humanitarian response.
• Temporal scale: Short‑term (seconds‑minutes warning), medium‑term (days‑weeks recovery) and long‑term (decadal rebuilding, hazard re‑assessment).

6.2 Hazard‑Risk‑Management System

The system can be summarised as:

1. Inputs: Tectonic setting, volcanic plumbing, population distribution, socio‑economic data.
2. Processes: Hazard generation (earthquake shaking, eruption), vulnerability assessment, risk perception formation.
3. Outputs: Risk level, preparedness actions, policy decisions, emergency response.

7. Quantitative Data & Interpretation (AO2)

7.1 Earthquake Frequency – Magnitude Relationship

Interpretation tip: Plot magnitude (log‑scale) against log‑frequency to obtain the Gutenberg‑Richter relationship – a fundamental tool for seismic‑hazard estimation.

7.2 Volcanic Eruption Frequency

8. Management Strategies (AO3 – Evaluation)

8.1 Mitigation Measures

• Hard‑engineering: Seismic retrofitting, base isolation, reinforced masonry, diversion dams for lahars, ash‑fall shelters.
• Soft‑engineering: Land‑use planning (avoid building on flood‑prone slopes), stringent building codes, community‑based risk education, insurance schemes.

8.2 Monitoring & Early‑Warning

• Seismograph networks, GPS crustal deformation, real‑time volcano gas and seismicity stations.
• Early‑warning systems (e.g., Japan’s J‑Alert, USGS ShakeAlert) provide seconds‑to‑minutes warnings that can save lives if coupled with public education.

8.3 Evaluation of Options

9. Case Studies Illustrating Perception & Management

9.1 2010 Haiti Earthquake

• Pre‑event perception: “Earthquakes do not happen here” → minimal building standards.
• Outcome: ~230 000 deaths; widespread infrastructure collapse.
• Lesson: Risk communication must challenge local myths and promote seismic‑resistant construction even where perceived risk is low.

9.2 Mount Etna, Italy – Repeated Low‑Intensity Eruptions

• Perception: Normalised risk leads to complacency among residents and farmers.
• Management: Continuous monitoring (INGV), tiered public alert levels, land‑use restrictions on high‑risk flanks.
• Evaluation: Monitoring offsets complacency, but economic dependence on agriculture hampers evacuation compliance.

9.3 1995 Kobe (Great Hanshin) Earthquake, Japan

• High perceived risk due to regular drills and school programmes.
• Response: Rapid emergency services, but many buildings collapsed because retrofitting was insufficient.
• Lesson: Alignment of perception with actual risk must be matched by appropriate engineering standards.

9.4 1991 Mount Pinatubo, Philippines

• Intense media coverage and a well‑coordinated government evacuation saved ~75 % of the at‑risk population.
• Perception shift: From “remote mountain” to “imminent threat”.
• Key factor: Integration of scientific monitoring with culturally‑sensitive communication (use of local languages, community leaders).

10. Implications for Risk Management

• Education & communication: Tailor messages to local beliefs; use schools, radio, social media and community leaders to correct misconceptions.
• Community involvement: Engage residents in hazard mapping and scenario planning to bring perceived and actual risk into alignment.
• Media partnerships: Provide journalists with accurate data and training to avoid sensationalism.
• Policy design: Incorporate cultural values, gender considerations and disability access when drafting evacuation orders, building codes and land‑use policies.
• Resilience building: Combine hard‑ and soft‑engineering approaches, supported by regular drills, post‑event reviews and inclusive risk education.

11. Suggested Diagrams (for classroom use)

1. Flowchart: Personal experience, media, culture, socio‑economic status → Risk perception → Preparedness actions.
2. World map highlighting major seismic and volcanic belts, with symbols for sub‑duction, rift and hot‑spot zones.
3. Graph of the Gutenberg‑Richter frequency‑magnitude relationship.
4. Comparison matrix of hard‑ vs. soft‑engineering mitigation options (strengths/limitations).
5. Systems diagram showing inputs, processes and outputs of the hazard‑risk‑management system.

12. Summary

Perception of risk links the geological reality of earthquakes and volcanic eruptions with the social‑psychological factors that drive preparedness and policy. For Cambridge AS & A‑Level Geography, students must be able to:

• Describe the tectonic origins and physical characteristics of earthquakes and volcanic eruptions.
• Identify physical, demographic and cultural vulnerability factors, including diversity and inclusion considerations.
• Explain how personal experience, media, culture and socio‑economic status shape risk perception.
• Interpret quantitative data such as magnitude‑frequency tables and eruption‑frequency charts.
• Evaluate mitigation and early‑warning strategies, recognising strengths, limitations and the role of perception.
• Use case studies to illustrate alignment or mis‑alignment between perceived and actual risk.

By integrating scientific knowledge with an understanding of human perception, future geographers can design risk‑reduction policies that are both technically sound and socially acceptable.