3.3.2 Impacts of and responses to Seismic Hazards

Question 1

Social impacts of seismic hazards

Answer 1

• Earthquakes can cause buildings to collapse, killing and injuring people, and leaving others homeless.
• Earthquakes and liquefaction can cause gas lines and power lines to break, starting fires that kill more people. Broken water pipes can cause flooding, and lack of water can make it hard to put fires out.
• Lack of clean water can cause disease to spend.
• Tsunamis can flood large areas, killing people and causing widespread damage to property.

Question 2

Economic impacts of seismic hazards

Answer 2

• Earthquakes can destroy business premises through ground shaking and liquefaction. This damages the economy of the region and the country.
• Damage to industry may mean that the country has to rely on expensive imports of goods and energy.
• Damage to buildings and infrastructure can be very expensive to repair.

Question 3

Environmental impacts of seismic hazards

Answer 3

• Industrial units, including power plants, can be damaged by earthquakes and tsunamis, causing leaks of chemicals or radioactive material that damage the environment.
• Fires started by damaged gas and electricity lines can destroy ecosystems.
• Tsunamis can flood freshwater ecosystems, killing plants and animals and salinising water and soil.

Question 4

Political impacts of seismic hazards

Answer 4

• Shortages of food, water and energy can cause conflict and political unrest.
• Governments may have to borrow money to repair damage, putting the country in deby. Money that is earmarked for development may have to be spent on repairing damage rather than on development.

Question 5

Prevention of seismic hazards

Answer 5

It’s not possible to prevent most seismic hazards.
However, it’s sometimes possible to prevent them posing a risk to people- e.g. authorities can prevent land that is prone to liquefaction from being built on, or build giant sea walls to prevent tsunamis hitting land.

Question 6

Preparation for seismic hazards

Answer 6

Preparedness is about preparing an area and the people who live there for a future seismic hazard. For example:

• Authorities can install earthquake warning systems these detect weaker seismic waves that may be a sign of a more powerful earthquake to come. The systems send out warnings by e.g. TV, radio and SMS.
• Individuals and businesses can have plans for how people should respond during an earthquake, e.g. staying away from buildings if possible, finding a strong door frame or desk to shelter under if inside.
• Authorities can develop tsunami warning systems and make sure evacuation routes are well signposted.
• Communities can set up search and rescue teams or fire response units to tackle the impacts of a hazard.

Question 7

Adapation for seismic hazards

Answer 7

People can adapt their behaviour or surroundings to minimise the risks of seismic hazards. For example:

• Buildings can be designed to withstand earthquakes, e.g. by using strong or flexible materials, or by building special foundations that absorb an earthquake’s energy.
• Buildings can also be designed to reduce vulnerability to tsunamis, e.g. tall, strong buildings allow people to escape the tsunami quickly, and buildings with raised, open foundations are less likely to be damaged.

Question 8

How are seismic hazards monitored?

Answer 8

Seismometers: A seismometer measures seismic activity by measuring motions in the ground.

Monitoring tremors: Tremors can be monitored to predict where they are likely happened, but not when they are likely to happen.

Animal behaviour: Research suggests there can be unusual animal behaviour prior to seismic events. For example, dogs barking incessantly, cows halting their milk, toads leaping from ponds.

Question 9

How are seismic hazards mitigated against?

Answer 9

Cross-bracing: A system used to reinforce buildings (particularly in HICs), where diagonal supports are put in buildings to increase the strength of a structure.

Computer controlled weights: Computer controlled weights can be used in the roofs of buildings to reduce movement by travelling around to specific places to balance out the movement of the building and help prevent it from toppling.

Rubber shock absorbers: Shock absorbers can be used on buildings and bridges to absorb seismic waves and reduce the impact of earthquakes.

Tsunami sea walls: Vertical seawalls are built in particularly exposed situations to reflect wave energy. They are typically constructed from concrete and built in tsunami-prone areas - such as Japan after they were hit by a tsunami in 2011.

Evacuation: Having pre-prepared evacuation protocols helps to limit the humanitarian damage of seismic events. Effective and quick evacuations are important.

Practice drills: Practice drills help to save lives in areas prone to seismic events as the population are aware of what to do in the case of a seismic event.

Early warning systems: These don’t predict earthquakes, they instead detect ground motion as soon as an earthquake begins and quickly sends alerts that a tremor is on its way, giving people very limited time to prepare.

Seismic dampers: A mechanical device that acts like a shock absorber to dissipate the kinetic energy of seismic waves passing through the building or other structures. These are designed to boost the structural integrity of a building and to protect against earthquakes. Used in HICs.