The Impact of Earthquakes

Factors that determine the damage caused:

• Time of day: night time = people asleep, no time to evacuate, everyone inside buildings
• Magnitude: stronger = more damage
• Depth of focus: shallow or deep?
• Distance from epicentre: Where are the shockwaves the strongest? How long do they last for?
• Population density: Lots of people = higher chance of loss of life
• Preventative measures: Are there earthquake-proof buildings or other measures to reduce the effect of earthquakes? 1st world vs 3rd world?
  • Economic wealth – LDCs (Less Developed Countries) will not be prepared as they have less money for things such as earthquake-proof buildings.

Effects of Earthquakes

Short Term:

• Loss of life
• Destruction of buildings
• Landslides/Avalanches
  • Can happen for days after, e.g. Nepal, 2015
• Tsunamis
  • Can occur if the earthquake happens under an ocean
  • E.g. South-East Asia 2004 – killing almost 250,000 people
• Disruption and damage to services
  • Water supply/sewage/gas
• Liquefaction
• Sand/Gravel mixes with water, turned into liquid mud which cannot support structures – leads to buildings collapsing

Long Term:

• Outward Migration
  • People leave the area, in turn leading to homelessness
  • 24,000 people left Nepal in 2015 and lived in makeshift camps as their homes were destroyed
• Disease
  • Exposed corpses, damaged sewage pipes all lead to the quick spread of disease as these can also affect the water supply
• Economic Slowdown
  • Shops/industry damaged, people lose their jobs, the economy diverted as money is spent on rescue operations and repairing damage, and tourism will decline due to safety fears

Limiting Earthquake Damage:

Strict planning laws are the best way to limit damage as earthquakes don't kill people – the side effects do e.g. falling buildings. Japan has strict planning laws – can't build in areas susceptible to liquefaction or on fault zones – and high standard of earthquake proof buildings with the following:

• Flexible columns to allow for swaying

• Rollers for side to side movement

• Fireproofing of old buildings – when gas pipes break, this can cause fires

• Deeper foundations for stability and cross beams to make them stronger However, LDC's do not have the same budget as Japan to enforce these changes and update buildings. They have more basic measures in place such as:

• Hollow, light blocks

• Low-rise structures

• Reinforced concrete pillars in the corner of buildings (equivalent to deeper foundations/cross beams)

• Items secured to walls – e.g. presses with cups/plates in them will have bars across the front to stop them falling out during an Earthquake

Measuring Earthquakes

Tools used to measure earthquakes:

• Seismograph
• Richter scale
• Mercalli scale

Seismograph:

• A machine that is sensitive to movement and detects, measures and records seismic waves.
• Primary waves/P-waves are the fastest waves that travel through molten material.
• Secondary waves/S-waves are slower as they travel through rock.
• Surface waves are the slowest and travel along the surface.

Richter Scale:

• Used to measure ground movement caused by an earthquake and its magnitude/strength. It is measured with a Seismograph.
• For every point on the scale the damage is increased 10 times.
• Example: a level 4 earthquake is 10 times stronger than a level 3 but 100 times stronger than a level 2.
• The most powerful earthquake ever recorded was 9.5 in Chile in 1960.

Mercalli Scale:

• Measures the damage caused by earthquakes. It is based on Human observations.
• Scale ranges from I to XII (1-12 in Roman Numerals)
• Example: III/3 would be objects hanging from the ceiling swaying back and forth.
• It only uses observations so is not as accurate or reliable as the other two.