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While we cannot prevent earthquakes or volcanic eruptions, we can significantly reduce their impact on human populations through effective management. The Edexcel B specification requires you to understand three main approaches to managing tectonic hazards: prediction, protection and planning. This lesson examines each approach, evaluates their effectiveness, and explains why management strategies differ significantly between high-income countries (HICs) and low-income countries (LICs).
Prediction involves attempting to forecast when and where a tectonic hazard will occur, ideally with enough warning time to evacuate people and prepare emergency responses.
The honest answer is: not reliably. Despite decades of research and billions of pounds invested, scientists cannot predict earthquakes with the precision needed (exact time, location and magnitude). However, several monitoring methods provide useful information:
| Method | How It Works | Effectiveness |
|---|---|---|
| Seismometers | Networks of instruments detect and record seismic activity. Patterns of small tremors (foreshocks) may precede larger earthquakes | Foreshocks do not always precede major earthquakes; many earthquake swarms do not lead to large events. Useful for identifying seismically active zones but not for precise prediction |
| GPS monitoring | Satellite-based GPS stations measure tiny movements of the Earth's crust (millimetres per year). Sudden changes in movement rates may indicate stress buildup | Helps identify areas where stress is accumulating but cannot tell us when it will be released. The technology is expensive |
| Gas emissions | Increased levels of radon gas seeping from the ground may indicate stress changes in rocks | Inconsistent — some earthquakes are preceded by radon increases, others are not. False alarms are common |
| Groundwater changes | Changes in the level or chemistry of groundwater in wells have preceded some earthquakes | Unreliable; changes can be caused by many factors unrelated to earthquakes |
| Animal behaviour | Reports of unusual animal behaviour before earthquakes (e.g., dogs barking, snakes emerging from the ground, birds abandoning nests) | Anecdotal and unscientific; no consistent, reliable pattern has been documented |
| Statistical probability | Scientists calculate the probability of an earthquake of a given magnitude occurring in a specific area within a given timeframe | Useful for long-term hazard assessment and planning but cannot predict individual events. Example: USGS estimates 60% probability of Mw 6.7+ in San Francisco Bay Area by 2043 |
Exam Tip: In exam answers about earthquake prediction, you should clearly state that reliable short-term prediction is not currently possible. However, long-term hazard assessment (identifying areas at risk and estimating probabilities) is well-established and very useful for planning purposes. Do not confuse prediction (forecasting individual events) with hazard assessment (identifying long-term risk).
Volcanic eruptions are more predictable than earthquakes because volcanoes give warning signs before erupting:
| Warning Sign | Explanation |
|---|---|
| Small earthquakes | Magma moving through rock causes swarms of small earthquakes beneath the volcano. Seismometers can detect these tremors weeks or months before an eruption |
| Ground deformation | As magma fills the magma chamber, the volcano swells. Tiltmeters and GPS detect this swelling, which may be only a few centimetres but is measurable |
| Gas emissions | Increased emissions of sulphur dioxide (SO₂) and carbon dioxide (CO₂) indicate that magma is rising and degassing. Gas-monitoring instruments at the crater detect these changes |
| Temperature changes | Thermal imaging from satellites and ground-based sensors can detect increased heat around the volcano, indicating rising magma |
| Changes to crater lake | Temperature, colour and chemistry of water in crater lakes may change as volcanic gases dissolve into the water |
Successful predictions include:
Protection involves designing and building structures and systems that can withstand tectonic hazards, reducing damage and casualties.
Modern engineering can dramatically reduce earthquake damage:
| Feature | How It Works |
|---|---|
| Base isolation | Buildings are placed on flexible pads (rubber or steel bearings) that absorb seismic energy, allowing the building to move independently of the shaking ground. Used in Japan's Narita Airport and San Francisco City Hall |
| Cross-bracing | Steel cross-braces in the walls and frame prevent the building from swaying and collapsing during shaking |
| Shear walls | Reinforced concrete walls that resist lateral (sideways) forces from earthquake shaking |
| Deep foundations | Foundations driven deep into solid bedrock rather than loose sediment, which is prone to liquefaction |
| Dampers | Large weights or hydraulic systems in tall buildings that counteract swaying (similar to a pendulum). The Taipei 101 tower in Taiwan has a 730-tonne tuned mass damper |
| Flexible frames | Steel frames that can flex and bend without breaking during shaking, absorbing seismic energy |
| Lightweight materials | Using lighter roofing materials (metal rather than heavy tiles) so that if the building collapses, less weight falls on occupants |
| Method | How It Works | Example |
|---|---|---|
| Tsunami barriers (sea walls) | Concrete walls along the coast designed to absorb or deflect tsunami waves | Japan has invested billions in tsunami walls up to 15 metres high along its Pacific coast. However, the 2011 Tōhoku tsunami overtopped many barriers |
| Breakwater systems | Offshore structures designed to reduce wave energy before it reaches the coast | Japan's Kamaishi breakwater (world's deepest at 63 m) reduced tsunami height by 40% but was still insufficient against the 2011 event |
| Tsunami warning systems | Networks of ocean buoys, seismometers and tide gauges detect tsunamis and issue warnings | The Pacific Tsunami Warning Center (est. 1949) monitors the entire Pacific. After the 2004 Indian Ocean tsunami, a warning system was established for the Indian Ocean (operational since 2006) |
| Natural defences | Mangrove forests and coral reefs absorb wave energy and reduce tsunami impacts | Studies after the 2004 tsunami found that coastal communities protected by mangroves suffered significantly less damage |
Exam Tip: Protection measures are generally more effective and more commonly implemented in HICs because they require significant financial investment, engineering expertise and enforced building codes. In LICs, the cost of earthquake-resistant construction may be prohibitive, and building codes may exist on paper but not be enforced in practice.
Planning involves preparing communities and governments for tectonic hazards through education, emergency procedures and land-use decisions.
| Strategy | Details |
|---|---|
| School earthquake drills | Japan conducts annual earthquake drills in all schools on 1 September (Disaster Prevention Day), teaching children to "Drop, Cover, Hold On". These drills save lives by making the response automatic |
| Public awareness campaigns | Governments distribute information about earthquake risks, evacuation routes and emergency supplies. In the USA, the "Great ShakeOut" drill involves millions of participants annually |
| Community preparedness | Training local volunteers in first aid, search and rescue, and emergency communication. Japan's community disaster prevention organisations (jishubo) are a model for other countries |
| Strategy | Details |
|---|---|
| Evacuation routes | Clearly marked evacuation routes for tsunamis and volcanic eruptions, with signs showing the direction to higher ground. Japan has tsunami evacuation towers and shelters in coastal communities |
| Emergency supplies | Governments and households stockpile emergency food, water, first aid supplies and batteries. Japan recommends households maintain a 72-hour emergency kit |
| Emergency communication | Earthquake early warning systems (like Japan's J-Alert) send alerts to mobile phones seconds before shaking arrives, giving people time to take cover |
| International cooperation | The UN's Sendai Framework for Disaster Risk Reduction (2015–2030) promotes global cooperation in reducing disaster impacts |
| Strategy | Details |
|---|---|
| Hazard mapping | Identifying areas at risk from earthquakes, volcanic eruptions, tsunamis, landslides and liquefaction, and restricting development in the highest-risk zones |
| Building codes | Setting legal standards for construction in seismic zones (e.g., all new buildings must be designed to withstand a certain magnitude of earthquake). Japan's building codes are among the strictest in the world |
| Exclusion zones | Areas around active volcanoes where no permanent settlement is allowed (e.g., the exclusion zone around Mount Merapi, Indonesia) |
| Insurance requirements | Requiring property owners in seismic zones to purchase earthquake insurance, encouraging risk-aware behaviour |
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