Intraplate earthquakes

Intraplate Earthquakes Case Studies

• Intraplate earthquakes occur in the centre of plates rather than at plate boundaries. There are no clear reasons why, but research suggests they link to reactivated plate weaknesses.

Case Study 1: New Madrid

• General information:
• Occurred December 16th 1811 - February 7th 1812
• Contained 3 main shocks - 7.5, 7.3 & 7.5-mag respectively
• Aftershock of first shock = 7.0 - there were 6 aftershocks in the first two days
• Hundreds of tremors felt into 1813
• Are has been an active seismic zone for 4,500 years
• Damage area was 600,000km^2 and perceptibility area was 5,000,000km^2
• First quake:
• Minimal structural damage - sparse epicentre population
• Environmental damage = sand blows, failed river banks, landslides, sunken land
• Felt across entire east USA
• Second quake:
• Smallest & least damaging
• Environmental damage = ground warping, ejections, fissuring, severe landslides, caved stream beds
• Third quake:
• The worst
• Completely destroyed New Madrid
• Severe housing damage in St. Louis
• Same environmental damage as previous

Slide 3

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• Legenda: Artist's impression of the earthquakes.

Case Study 2: Gujarat

• General information:
• Occurred Friday 26th January 2001 (8:46 local time)
• Epicentre in Bhuj, Gujarat, NW India (400 miles from plate boundary)
• 20,000 confirmed dead, 166,000 injured, 600,000 homeless, 844,000 homes damaged, 350,000 homes destroyed
• Damage costs between $1.3 million and $5 million
• Environmental damage = liquefaction, flow of "desert" rivers, new springs (some salt water)
• Transport:
• Road damage - limited goods transportation to 40 ports
• Remote villages inaccessible for days (rescue services hindered) - warped roads & fallen debris
• Phone lines & signal towers broken - no communication in remote places
• Industry:
• Industries disrupted - lack of communications, transport and energy supplies (plus the death toll)
• Few factories destroyed
• Aftermath - industry losing $200 million per day
• Services:
• General services damaged - water, gas, electricity, sewerage
• Loss of fresh water
• Sewerage discharge
• 95% of Bhuj uninhabitable - no fresh water, shelter or electricity

Slide 5

Source List

• geolsoc.net
• earthquake.usgs.gov
• geographysite.co.uk