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Spec mapping (AQA 7037): Paper 1 (Physical), §3.1.5 Hazards — seismicity: detailed case studies of seismic events at contrasting locations and scales, demonstrating their causes, impacts (primary/secondary; social, economic, environmental) and responses (prediction, monitoring, management, including the modification of vulnerability and resilience). This lesson applies the fault-mechanics, wave-physics and measurement theory of the previous lesson to four contrasting earthquakes — Haiti 2010, Chile 2010, Tōhoku (Japan) 2011 and Nepal 2015 — selected to vary both physical magnitude and development/governance context so that the risk equation can be tested directly. It links to the boundary processes of §3.1.5, to §3.2 (population/urban vulnerability) and to the management lesson. Assessment objectives: AO1 (the events and their hazards), AO2 (applying tectonic and vulnerability theory to each located case) and AO3 (comparing and evaluating magnitude, casualty and economic data across development contexts).
A note on the magnitudes quoted: official agencies sometimes report slightly different values for the same earthquake (the USGS, for instance, lists Tōhoku at Mw 9.1 and some sources at 9.0; Haiti's death toll is reported anywhere from ~160,000 to over 300,000 depending on the source and methodology). These differences do not affect the argument — what matters is the order of magnitude of the contrasts and the reasons behind them — but they are themselves a useful reminder, exploited in the AO3 work below, that even the headline figures of a disaster carry uncertainty and, in the case of death tolls, can be politically contested.
The defining analytical question of this lesson is the one AQA returns to in nearly every essay cycle: why do earthquakes of comparable magnitude kill vastly different numbers of people? The four cases are chosen as a natural experiment. Haiti and Chile both struck in 2010, only weeks apart, yet Chile's earthquake released ~500 times more energy than Haiti's and killed hundreds, while Haiti's killed hundreds of thousands — the single most powerful illustration in all of physical geography that the Vulnerability and Capacity terms, not the Hazard term, usually determine the death toll. Holding the risk equation, Risk=(Hazard×Vulnerability)/Capacity, in view throughout, the task is to use precise, located figures to explain which term dominated in each case — and to recognise that the answer is conditional, because at the extreme upper end (Tōhoku) a great tsunamigenic hazard can overwhelm even the highest capacity on Earth.
A note on technique: examiners reward figures deployed to evidence an argument, not a recital of facts. For each case below, the data are tied to an explanation — magnitude to the Hazard term, building quality and poverty to Vulnerability, governance and warning systems to Capacity — and that is the model to imitate.
It is worth being explicit at the outset about the full set of factors that shape an earthquake's impact, because a strong answer works systematically through them rather than reaching for whichever comes to mind. The physical factors include magnitude (energy released), focal depth (shallow events being far more destructive at the surface), distance of the epicentre from population centres, local ground conditions (soft sediments amplify and prolong shaking; saturated ground liquefies), and the presence of secondary hazards (tsunami, landslides, fire). The human factors include population density and the proportion living in vulnerable locations; building quality and whether seismic codes exist and are enforced; the level of economic development and the resilience it buys; the quality of governance and institutions; the existence and effectiveness of warning, education and emergency-response systems; and even the time of day, which determines where people are when the shaking strikes. The four cases below are chosen precisely because they vary these factors against one another — sometimes a large magnitude meets high capacity (Chile, Tōhoku), sometimes a moderate magnitude meets extreme vulnerability (Haiti) — so that their relative importance can be weighed.
| Category | Details |
|---|---|
| Deaths | Estimated ~160,000–230,000+ (figures disputed and politicised) |
| Injured | Over 300,000 |
| Displaced | ~1.5 million into temporary camps |
| Infrastructure | Presidential palace, parliament and most ministries collapsed (decapitating the government); 250,000+ homes and 30,000+ commercial buildings destroyed; port and airport crippled |
| Economic | ~US$7.8–8.5 billion in damage — over 100% of GDP |
| Secondary/tertiary | A cholera outbreak, inadvertently introduced by UN peacekeepers, killed ~9,000 more in the following years |
Haiti is the archetype of a disaster driven by Vulnerability and Capacity, not by the size of the Hazard. The magnitude (Mw 7.0) was only moderate, but four human factors converted it into one of the deadliest earthquakes in history: a very shallow focus directly beneath a capital city (maximising surface shaking where people were densest); a building stock of unreinforced masonry and poorly-detailed concrete that pancaked instantly; extreme poverty leaving no resilience; and the collapse of the state itself — government buildings, the UN mission headquarters, hospitals and the port all failed, so the very institutions that should have led the response were destroyed. The immediate response was therefore slow and chaotic: the Dominican Republic provided the first cross-border aid, and the US military reopened the airport and deployed the carrier USS Carl Vinson, but the destruction of local capacity left a vacuum. Over US$13 billion was pledged internationally, yet long-term recovery was extremely slow and widely criticised — tens of thousands remained in camps years later, and questions about NGO effectiveness (notably the Red Cross's poor delivery of permanent housing despite raising vast sums) became a case study in the limits of top-down aid. The cholera epidemic deserves note as a tertiary hazard: it was not caused by the earthquake directly but by the conditions the earthquake created — destroyed sanitation, displaced people crowded into camps, and a pathogen inadvertently introduced by the relief operation itself. It went on to kill ~9,000 people, more than many entire earthquakes, demonstrating how in a low-capacity setting the secondary and tertiary consequences of a disaster can rival the primary event, and how recovery is not a single phase but a long, fragile period during which new hazards emerge. Haiti's experience also raises uncomfortable questions about whether large inflows of uncoordinated aid and competing NGOs can sometimes undermine the rebuilding of local governance and capacity that genuine recovery requires — a debate that runs directly into the management lesson.
| Category | Details |
|---|---|
| Deaths | ~525 (a tiny fraction of Haiti's, from a vastly larger earthquake) |
| Displaced | ~800,000 affected; ~370,000 homes damaged |
| Tsunami | A local tsunami struck the coast within ~20–30 minutes, killing many of the victims; warning communication failed in places |
| Economic | ~US$30 billion in damage (~15–18% of GDP) — high in absolute terms because the country has more to lose |
| Infrastructure | Modern buildings largely survived; older structures and some bridges/highways failed |
Chile is the indispensable companion to Haiti. A far larger earthquake (Mw 8.8 versus 7.0) killed perhaps three orders of magnitude fewer people (~525 versus up to ~230,000). The Hazard term was enormously bigger; the outcome was far smaller — which can only be explained by the human terms of the equation. Chile's enforced seismic codes meant most buildings flexed rather than collapsed; its wealth and stable governance meant functioning institutions, a resourced military and rapid self-reliant response; and its long cultural experience of earthquakes meant a prepared population. The principal failure was in the tsunami warning, which was not reliably communicated to coastal communities, so a significant share of the deaths came from the wave rather than the shaking — a pointed reminder that even a high-capacity country has specific weaknesses, and that secondary hazards require their own warning chains. The Haiti–Chile pairing is the most-cited evidence in the whole topic that development (Capacity) can decouple a huge hazard from a huge death toll.
The comparison is so powerful precisely because it functions like a controlled experiment. The two events occurred within six weeks of each other, removing any argument that the difference reflects changing global conditions or warning technology over time; both involved major earthquakes affecting significant cities; and both countries are in the same hemisphere on the same Pacific margin. The principal variable that differs is development and the capacity and reduced vulnerability it confers — and the magnitude difference, far from explaining the death tolls, runs in the opposite direction to them. There is even a further analytical layer worth drawing out: Chile's deeper focus (~35 km versus Haiti's ~13 km) and its offshore epicentre (~100 km from Concepción versus Haiti's ~25 km from central Port-au-Prince) meant that the physical exposure of the densest population was actually lower in Chile despite the larger magnitude, reinforcing rather than undermining the human-factors interpretation. A candidate who can articulate why Haiti–Chile is close to a natural experiment, and who notices the focal-depth and epicentre-distance nuances, is operating at the top of the mark scheme.
| Category | Details |
|---|---|
| Deaths | ~18,500 — over 90% from the tsunami, not the shaking |
| Displaced | ~470,000 at peak |
| Tsunami | Waves up to ~40 m in places; ran up to ~10 km inland on the Sendai Plain; ~561 km² inundated |
| Nuclear | Fukushima Daiichi lost cooling when the tsunami overtopped its sea wall; three reactors melted down; ~154,000 evacuated from the exclusion zone; decommissioning will take 30–40 years |
| Infrastructure | ~130,000 buildings totally destroyed; roads, railways and ports severely damaged |
| Economic | ~US$235 billion — the costliest natural disaster in history |
Tōhoku is the case that qualifies the development thesis. Japan did almost everything right: its Earthquake Early-Warning System detected the P-waves and issued 8–30 seconds of warning, automatically stopping bullet trains and halting industrial processes; its building codes (toughened after the 1995 Kobe earthquake) meant that most modern structures survived even Mw 9.0 shaking with little damage, so very few died from building collapse. And yet ~18,500 people still died — because the tsunami exceeded the design height of the coastal defences. Many sea walls were 5–10 m; the waves reached 15–40 m and simply overtopped them, including at Fukushima Daiichi, where the loss of cooling triggered the nuclear disaster. The lesson is profound and examinable: beyond a certain magnitude, the Hazard term can overwhelm even the highest Capacity. High development did not fail — it kept the shaking deaths to a handful and enabled a rapid, well-resourced response (100,000 Self-Defence Force troops deployed within days) — but it could not eliminate the tsunami's toll, and it shifted the catastrophe into a technological (nuclear) dimension. Reconstruction has cost over US$300 billion and included controversial new sea walls up to ~15 m and the relocation of some communities to higher ground.
The Fukushima dimension repays attention because it illustrates a distinctively modern form of hazard impact — the cascading, multi-hazard, technological disaster. The chain ran: earthquake → tsunami → loss of off-site power and flooding of the backup generators → loss of reactor cooling → meltdown and hydrogen explosions → radioactive release → mass evacuation of ~154,000 people and the creation of a long-term exclusion zone. No one died directly from radiation, but the evacuation itself caused deaths among the elderly and vulnerable, the economic and psychological toll was immense, and Japan's subsequent shutdown of its entire nuclear fleet reshaped national energy policy and raised carbon emissions — a synoptic link to the energy and climate content elsewhere in the specification. The deeper lesson is that high-capacity, technologically-complex societies are exposed to new kinds of vulnerability: the more sophisticated and interconnected the infrastructure, the more ways a natural trigger can cascade into a compound catastrophe. This is a recurring theme of the multi-hazard lesson and a powerful counter to any naïve assumption that development simply makes places safer — it makes them safer from some hazards while exposing them to others.
A final analytical point on Tōhoku concerns the danger of designing for the historical rather than the physically possible maximum. Japan's sea walls had been built to withstand the largest tsunami in the instrumental and historical record, but palaeotsunami deposits (and the AD 869 Jōgan event) hinted at far larger events that fell outside the planning horizon. Designing defences to "the worst that has happened" rather than "the worst that can happen" is a systematic weakness in hazard planning worldwide, and Tōhoku is its defining cautionary tale — one with direct relevance to climate-driven hazards whose magnitudes are now exceeding all historical precedent.
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