Hazard, exposure and vulnerability
Separate physical intensity from exposure and support needs, then compare preparedness choices.
Hazard, exposure and vulnerability
Compare earthquake preparedness choices using the hazard map, household assumptions and stakeholder evidence. The resources describe one fictional teaching scenario.
Earthquake preparedness: hazard and occupied-home layers
Scroll the diagram sideways to see the full resource.
| District | Hazard category | Occupied homes | Vulnerability index (ordinal 1–3) |
|---|---|---|---|
| A | High | 180 | 1 |
| B | Medium | 70 | 1 |
| C | High | 90 | 2 |
| D | Low | 180 | 3 |
Resource description
A: High hazard, 180 occupied homes, vulnerability index 1; B: Medium hazard, 70 occupied homes, vulnerability index 1; C: High hazard, 90 occupied homes, vulnerability index 2; D: Low hazard, 180 occupied homes, vulnerability index 3. The vulnerability index is ordinal, not a probability.
Scenario exposure and support assumptions
| District | Scenario-exposed homes (%) | Share needing support among exposed homes (%) | Expected homes needing assistance (model value) |
|---|---|---|---|
| District A | 30 | 75 | 40.5 |
| District B | 50 | 25 | 8.75 |
| District C | 60 | 25 | 13.5 |
| District D | 60 | 25 | 27 |
Resource description
Teaching assumption: assistance = occupied homes × scenario-exposed share × support-needing share. The ordinal vulnerability index is not multiplied into this calculation. Shares are supplied fictional assumptions, not probabilities inferred from map categories.
Management alternatives
| Option | Capital cost (£ million) | Benefit | Limitation |
|---|---|---|---|
| Warning and evacuation support | 1.8 | Can improve access to warnings and assistance | Does not reduce the physical hazard; response and accessibility matter |
| Strengthen vulnerable buildings | 5.8 | Can reduce structural vulnerability in priority areas | Coverage is limited by the budget and implementation time |
| Protect emergency access routes | 3.2 | Supports rescue and supply movement | Homes may remain exposed and vulnerable |
Resource description
Available capital budget: £6 million. Options are alternatives; their benefits cannot simply be added. Operating costs are separate.
Options
Warning and evacuation support
Capital cost: £1.8 million
Can improve access to warnings and assistance
Does not reduce the physical hazard; response and accessibility matter
Strengthen vulnerable buildings
Capital cost: £5.8 million
Can reduce structural vulnerability in priority areas
Coverage is limited by the budget and implementation time
Protect emergency access routes
Capital cost: £3.2 million
Supports rescue and supply movement
Homes may remain exposed and vulnerable
Stakeholder statements
Residents of the most exposed district: We need warnings we can act on and help for people unable to leave.
Emergency coordinator: The expected support total is 89.75 homes (a model expectation, not an observed count); emergency routes must remain usable.
Building engineer: Reducing vulnerability takes time and cannot promise zero damage.
Resource assumptions
- Hazard and vulnerability categories are ordinal; multiplying them does not give a loss probability.
- The assistance formula is an explicit teaching assumption, not a real loss model.