3.1.5.4 Seismic hazards Flashcards
Define tsunamis
- giant sea wave caused by shallow focus earthquakes
- long wavelength
- travel quickly
- large wave height
Define liquefaction
When violently shaken soils with high water content lose their mechanical strength and become fluid
Define shockwaves and seismic waves
Two main types of seismic waves:
- P waves (6km per hour, through solids and liquids)
- S waves (3km per hour, and cannot travel through liquid)
Define landslides
A slope failure as a result of the ground shaking
Describe the spatial distribution of earthquake
- majority occur on plate boundaries
- few can occur with the reactivation of old fault lines
- human activity can induce earthquakes (Taylor Swift concert induced a magnitude 2)
Name the 3 methods of measuring earthquakes
- Richter scale (logarithmic 1-10)
- moment magnitude scale (measures energy release)
- Mercalli scale (measures intensity by its impact upon people)
How can you predict earthquakes
It is very difficult but you can monitor:
- crustal movement
- strange animal behaviour
How can you protect against earthquakes (4)
- ensure safety drills are well practiced
- building hazard resistant structures
- land use planning
- fire prevention (smart meters can cut off gas under shaking)
When was the Haiti earthquake
2010
Where was the epicentre of the Haiti earthquake
24km south-west of capital Port-au-Prince
How deep was the focus of the Haiti earthquake
13km
What percentage of the population of Haiti live below the poverty line
40%
Primary effects of the Haiti earthquake (social x3)
- 230,000 dead
- 1.5 million people homeless
- 50% of buildings destroyed, including 80% of schools (due to liquifaction)
What was the magnitude of the Haiti earthquake
7.0
Secondary effects of the Haiti earthquake
- aftershocks of 6.1 magnitude
- with the 25% of civil servants dying and the destruction of official buildings, the government was crippled
- city became lawless
- cholera outbreaks
Immediate responses of the Haiti earthquake (governmental, social x2)
- 16,000 US troops restored law and order
- bottled water and purification tablets for 250,000 people
- over 1,100 camps to shelter 1.5 million people
Long term responses of the Haiti earthquake (econ, social, econ)
- $11.5 billion in aid
- unemployed people paid to reconstruct key buildings
- economic activities centred away from Port-au-Prince
When was the Tohoku earthquake, Japan
2011
How many earthquakes does Japan have in a year
1500
What was the magnitude of the Tohoku earthquake
9.0
How long after the earthquake did the first tsunami hit
30 minutes
Primary effects of the Tohoku earthquake (3)
- limited damage from the earthquake due to earthquake proof buildings
- 18,000 dead or missing due to the tsunami
- warning system saved many lives
Secondary effects of the Tohoku earthquake (3, social)
- 500,000 homeless
- over 700 aftershocks
- explosions and radiation leaks at Fukushima Daiichi nuclear power plant
- fears of nuclear disaster caused panic seling
Immediate responses of the Tohoku earthquake (3, UK)
- 100,000 soldiers mobilised to establish order
- UK sent 63 search and rescue specialists
- an exclusion zone around Fukushima Daiichi and then the government shut down nuclear plants
Long-term effects of the Tohoku earthquake (future, social, economic)
- future contingency plans against tsunamis (new warning system in 2013)
- 100,000 residents not returned home 5 years later
- $300bn in damages
