Earthquakes Flashcards
At which two plate boundaries do most earthquakes take place?
Destructive and Conservative.
How are earthquakes caused?
By great stresses between rocks from different plate boundaries. Earthquakes occur when lots of seismic energy is released at once, which is due to tectonic plates moving in a stick-slip fashion.
Which two scales are used to measure earthquake magnitudes?
- Richter scale, the original scale from the 1930’s.
- The moment magnitude scale (Mw) developed in the 1970’s to replace the Richter scale.
What type of earthquakes are more dangerous, shallow or deep earthquakes?
Shallow
What are aftershocks?
Smaller tremors in the lithosphere as the tectonic plates move around after the major earthquake, but can still be very strong and deadly.
What is the epicentre?
The point at the top of the earths crust directly above the focus.
What is the focus?
The centre of the earthquake/ where the seismic waves travel from.
When was the Tōhoku earthquake in Japan?
March 2011, in North east Japan.
Tōhoku earthquake facts.
- 9 Mw and only 30km below sea level therefore very shallow
- Triggered 6-7Mw aftershocks and a tsunami
- Tsunami travelled at over 800kmh and hit the East coast of Japan at 10m in height and reached as far as 10km inland, as well as reaching Hawaii at 3.5m and California at 2.7m.
- Damage over US$300 billion, US$235 billion of which was in Japan alone.
Primary impacts of Tōhoku earthquake
- Between 667 and 1479 deaths from earthquake
- Most deaths from collapsing buildings
- Infrastructure hugely damaged
- Reclaimed land in Tokyo suffered from liquifaction, where land turns to liquid, damaging over 1000 buildings.
Secondary Impacts of Tōhoku earthquake
- 17000+ deaths from tsunami, half of which were over 65 years old
- 5000 injured or reported missing
- 127000 buildings collapsed and 1.2 million buildings severely damaged
- Fukushima Dam damaged
- Nuclear meltdown as main power was cut and the back-up generator destroyed by the tsunami. Businesses suffered without electricity.
Protection for Tōhoku earthquake
- Advanced warnings
- International Aid from countries and NGO’s
- 130000 displaced in shelters and 140000 evacuated in 20km radius around Fukushima power station
- Every September 1st people in Japan are drilled for natural disasters (National Disaster Prevention Day)
Haiti earthquake 2010
- LDC poorest country in Western hemisphere
- 7Mw earthquake 25km south-west of the capital Port-au-Prince, focus was very shallow (13km below surface).
- Caused by contraction and deformation along a fault near the conservative plate boundary between the North American and Caribbean plate.
Primary impacts of the Haiti earthquake
- 316000 dead and 300000 injured
- 3 million affected and 1.5 million homeless
- All 8 hospitals collapsed
- All 3 universities collapsed
- Port-au-Prince severely damaged and airport tower collapsed, so initially there was no airport to allow aid to reach Haiti, as Haiti is an island and it’s port was ruined.
Secondary impacts of the Haiti earthquake
- Factories closed and tourism stopped leading to huge economic loss
- Looting and crime increased as police force and gov’t collapsed as their buildings collapsed
- Chlorea epidemic began 10 months after, killing over 8000 and infecting 6% of all Haitians by 2013
