9. Managing Seismic Events Flashcards
Examples of prevention
- Fault lubrication
- Altering properties of soils
- Managed forests
How does fault lubrication work?
Pumping water into fault plane allowing it to move more easily and frequently therefore, generating smaller, non-damaging earthquakes rather than storing up energy for a major earthquake.
How does altering properties of soils work?
Drilling boreholes into the ground in such a way that the properties of soil are changed so that incoming earthquake waves would be reflected.
Additionally, concrete pillars could be dug into the ground to act as a seismic cloak to protect buildings.
How do managed forests work?
Planting trees between buildings and a potential earthquake source.
The trees are planted in a wedge shape with tallest trees near to the earthquake source.
The Forest resonates with the most powerful seismic waves converting them into less destructive shear waves that travel down into the crust where they can do no harm.
What is the effectiveness/ sustainability of the prevention techniques?
Technology is largely untested.
Question marks over amount of water required also suggests that fault lubrication is unfeasible and unsustainable.
Examples of prediction
Scientists have identified a number of events that occur before an earthquake strikes:
- Microquakes before main event
- Bulging of ground
- Decreased radon gas concentrations in groundwater
- Raised groundwater levels
- Electrical and magnetic changes within local rocks
- Increased argon gas content in soils
- Curious animal behaviour
How does prediction work?
Use seismometers to detect changes and monitor
Use to create seismic hazard maps and model the likely impacts of an earthquake on a locality.
Technology has allowed early warning systems such as shake alert
What is the effectiveness/sustainability of prediction?
Prediction is very difficult, if not impossible at the current levels of technology
Examples of adaptation/ mitigation
Hazard resistant structures:
- Large concrete on top of buildings
- Large rubber shock absorption foundations
- Cross bracing
- Retrofitting
- Hollow bricks, mud bricks, straw bricks
How does large concrete blocks work?
Moves with the aid of a computer programme, in the opposite direction to the force of the earthquake in order to counteract stress
How do shock absorbers work?
Allows some movement of buildings
How does cross bracing work?
Hold buildings together better when it shakes
How does retrofitting work?
Existent buildings are adapted to make them more earthquake proof
How do hollow/ mud/ straw bricks work?
Lightweight to make buildings less dangerous if they fall down
What is the effectiveness/ sustainability of adaptation/ mitigation?
Strategies are expensive so not everyone will be able to afford/ access them
Effective but costly
Examples of preparation
- education
- fire prevention
- emergency services
- land use planning
- insurance
- aid
- tsunami protection
How does education work?
Instructions issued by authorities on how to prepare for such events by securing homes, appliances and heavy furniture, teaching children.
How does fire prevention work?
Smart meters developed to cut off gas if an earthquake of sufficient magnitude occurs.
How do emergency services work?
Heavy lifting gear needs to be available, first aid training
How does land use planning work?
Most hazardous areas identified and then regulated, have sufficient open space, put certain types of building in areas of low risk e.g. schools and hospitals
How does insurance work?
Richer areas, people are encouraged to take out insurance to cover losses
How does aid work?
Provide medical services, tents, water purification equipment, search and rescue equipment
How does tsunami protection work?
Automated systems installed to give warnings, the best of which uses bottom pressure sensors, attached to buoys, which constantly measure the pressure of the overlying water column.
Monitors earthquake activity and issues warnings to countries around Pacific edge if tsunamis are likely.
Effectiveness/ sustainability of preparation
- Lack of education in some areas, low socio-economic status have less access
- Smart meters won’t detect smaller magnitudes
- Emergency services needs careful and thorough organisation
- Good to form safe areas people can go to and reduce vulnerable areas
- Aid over long term can be problematic and can take days to come as it can increase death toll
- Tsunamis cannot be entirely predicted even if location and magnitude of earthquake is known
