What this lesson teaches
I can judge how well strategies before a disaster build a community's resilience.
Syllabus K329, Topic 4.3, Key Question 3. How effective are the strategies in building communities' resilience to earthquakes and volcanic eruptions?
Make a guess
A town plans a new hospital. One site is on a mapped fault zone, the other is outside it. What reduces risk most simply?
- Wait until after an earthquake to decide.
- Build on the site outside the fault zone.
- Build on the fault and add extra concrete.
- It makes no difference where it goes.
Show the answer
Build on the site outside the fault zone.
Avoiding new exposure is usually easier and cheaper than protecting a building in a danger zone, or moving it later.
Keep new building out of danger zones where possible, and strengthen the buildings and services that must stay.
Land-use planning can stop homes and key facilities, like hospitals, being built in fault-rupture zones, on unstable slopes, in tsunami flood areas and in lava paths. Avoiding new exposure is usually easier than moving a whole town later. Use a separate map for each hazard: a site outside the lava zone may still face lahars or ash.
Hazard-resistant design helps buildings survive. For earthquakes, stronger joints and bracing hold buildings together. Ductile structures bend without snapping. Dampers absorb energy to reduce swaying. Base isolation stops much of the ground's movement passing into the building. The right choice depends on the site and building. Retrofitting upgrades old buildings, but is often costly.
Design only works with suitable materials, skilled builders, inspection and maintenance. Rules that are ignored give little protection. Poorer families may need money or technical help. Upgrading old buildings can also disrupt homes and businesses for a time.
Relocation, moving people away, can cut exposure, but it can harm jobs, transport access and community ties. Consult residents, explain the evidence, and offer support and affordable options. Otherwise, people may just move to another unsafe place.
Community resilience also needs organisation. Trusted local networks know who lives alone or needs help, share information and keep plans up to date. Authorities can add expertise and money. Even strong buildings depend on working water, power and roads.
- Land-use planning
- Keep new building out of hazard zones.
- Base isolation
- Stops ground movement reaching a building.
- Retrofitting
- Strengthening old buildings.
Step by step
Choose safer sites
Build away from mapped hazard zones.
Strengthen buildings
Design and retrofit for the forces expected.
Keep it working
Inspection, maintenance and community support.
Real examples to use
Chile
Strict building codes, updated after past earthquakes, helped most buildings survive the magnitude 8.8 earthquake of 2010.
Taipei 101, Taiwan
This skyscraper has a huge steel ball, a tuned mass damper, that swings to reduce the building's sway in earthquakes and typhoons.
Worked example: The whole service matters
An earthquake-proof clinic may stay standing but still be useless if its water, power and only road fail. Resilience means planning for these links too.
Watch out for this
Earthquake-resistant buildings cannot be damaged.
They reduce risk, but extreme shaking, poor construction or failed services can still cause harm.
Check your understanding
How do safer siting and building strengthening differ?
- Both reduce the hazard, by making the shaking weaker.
- Siting cuts exposure; strengthening cuts vulnerability.
- Building rules move families out of the most dangerous areas.
Show the answer
Siting cuts exposure; strengthening cuts vulnerability.
Yes. They work in different ways.
Check your understanding
Chile's magnitude 8.8 earthquake in 2010 killed fewer than 800 people. What mainly kept the death toll low?
- Few people lived near the epicentre, which was offshore.
- Strict building codes and long experience of earthquakes.
- The shaking was weak, because the earthquake was deep.
Show the answer
Strict building codes and long experience of earthquakes.
Strong buildings reduce vulnerability.