Tectonic Hazard Profiles (Edexcel A Level Geography)

Earthquake magnitude

• Magnitude is the most common way to measure an earthquake
• It measures the energy released at the source (focus)
  • The magnitude can be measured on different scales but the one which is reported on the news when a earthquake occurs is the Moment Magnitude Scale (MMS)
  • It is measured using seismographs
• The MMS goes from 1 which are not felt by humans to 10
• The MMS is a logarithmic scale which means that a 6 on the scale is a ten times increase in amplitude from a 5 
  • The energy release is 32 times greater

Magnitude of earthquakes

Earthquake intensity

• The intensity of an earthquake is its impact on people, as well as the built and natural environments
• The Modified Mercalli Intensity Scale is used to measure the intensity
• The scale goes from I to XII

Modified Mercalli Intensity Scale

Measuring volcanic eruptions

• Every eruption is unique some are gentle, others are hugely explosive
• The Volcanic Explosivity Index (VEI) is used to measure the size of an eruption
• This can not be measured on a scientific instrument so is calculated based on a series of measurements and observations
  • These include:
    • Height of material ejected into the atmosphere
    • Volume of material
    • Duration of the eruption
• This is a logarithmic scale from 0-8 

Volcanic Explosivity Index

• Hazard profiles can be used to compare tectonic hazard events
• Hazard profiles usually include information about:
  • Magnitude
  • Speed of onset
  • Areal extent
  • Duration
  • Frequency
  • Spatial predictability

Hazard profiles of tectonic hazards

Advantages 

• Hazard profiles can be used to compare:
  • Different hazards
  • Same hazards with different processes - a volcano on a destructive boundary compared to one on a constructive boundary
  • Same hazards with different human vulnerabilities - an earthquake in a developed country compared to one in a developing country
• They can also be used to plan for future events
• They are useful when looking at one hazard such as an earthquake 

Disadvantages

• Hazard profiles do have disadvantages:
  • Other factors may have a greater influence on the impact
  • They focus on physical factors when human factors may be the most important
  • Multi-hazard events are not easily represented on a hazard profile 
  • They are subjective 

Earthquakes

Example	Profile Features	Social impacts	Economic impacts
Haiti (Developing) - 7.0 magnitude	Rapid onset Damage focussed on Port au Prince but extended over much of south Haiti Lasted 30 seconds	220,000 deaths 300,000 injured 1.5 million homeless 70% of buildings collapsed Disease spread	Damages US$7.8 billion Agriculture destroyed Unemployment increased  Exports decreased
Sulawesi, Indonesia (Emerging) - 7.5 magnitude	Rapid onset Strongest shaking in Palu City	4,340 deaths  10,670 injured 206,500 homeless Health risks	Damages US$1.3 billion Tourism affected Palu IV bridge collapsed Infrastructure damage
Amatrice, Italy (Developed) 6.2 magnitude	Rapid onset Strongest shaking felt in Amatrice - shaking felt by over 200,000 people Lasted 20 seconds	299 deaths  388 injured 4,500 homeless	Damages over US$4 billion Negative impact on tourism Many agricultural buildings were damaged