Managing Tectonic Hazards

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).

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Prediction

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.

Can We Predict Earthquakes?

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).

Can We Predict Volcanic Eruptions?

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:

• Mount Pinatubo, Philippines (1991): Scientists from the Philippine Institute of Volcanology (PHIVOLCS) and the US Geological Survey monitored increasing earthquakes, ground swelling and SO₂ emissions for weeks before the eruption. Over 60,000 people were evacuated from the danger zone, saving an estimated 5,000–20,000 lives.
• Mount St Helens, USA (1980): Two months of earthquakes and a visible bulge on the mountain's north face prompted evacuation of surrounding areas, significantly reducing the death toll (57 killed, but thousands of lives saved by the evacuation zone).

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Protection

Protection involves designing and building structures and systems that can withstand tectonic hazards, reducing damage and casualties.

Earthquake-Resistant Building Design

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

Tsunami Protection