STRUCTURE OF THE EARTH
The Earth has four layers - inner core, outer core, mantle and crust
Core - iron and nickel
- hot and dense
- outer core is molten, inner core is solid
Mantle - Semi-molten liquid
- Heat from the core creates convection currents
Crust - Thin layer of rock
PLATE TECTONICS AND CONTINENTAL DRIFT
The crust is made up of plates
The convection currents in the mantle cause continental drift
<--These are some of the plates
LOCATION OF EARTHQUAKES
Longitude - How east or west you are
Latitude - How north or south you are
Earthquakes occur at plate boundaries in linear patterns
WHAT HAPPENS AT PLATE BOUNDARIES
Where plates are moving apart
Magma rises in the gap and can escape easily - so eruptions are quite gentle
Where an oceanic plate moves towards and under a continental plate - it gets subducted
The oceanic crust then turns to magma because of the heat and pressure
Get both earthquakes and volcanoes
Where plates move side by side - opposite directions or same direction
Earthquakes occur is the plates get stuck then suddenly 'jerk' past each other
WHAT HAPPENS IN AN EARTHQUAKE?
Earthquake – A sudden movement within the earth’s surface, usually close to a plate boundary
Magnitude – The amount of energy that is given out during an earthquake
Focus – This is the point underground where the earth’s plates have moved
Epicentre – The point on the surface directly above the focus
Seismic waves – These are waves of force that travel through the earth.
Seismometer –An instrument used to measure the movement of the earth’s surface. A seismometer records the vibrations from earthquakes.
Seismograph – A graph produced by data collected from the seismometer - shows the shaking of the earth
Aftershocks – Smaller earthquakes formed as the crust around the displaced fault adjusts to the effects of the main shock.
PRIMARY AND SECONDARY EFFECTS
Happen straight away directly from the ground shaking
- Buildings collapse, windows shatter, bridges collapse
Happen as a result of the primary effects.
- Fires (from ruptured gas mains), disease, dirty water, buildings collapse due to liquefaction (explained below)
When soft sediment behaves like quicksand during an earthquake. This is because the shaking brings water to the surface which buildings sink into.
LEDC CASE STUDY - HAITI 2010
MEDC CASE STUDY - JAPAN (KOBE) MARCH 2011
COMPARING THE EFFECTS
- Not much money for equipment and supplies
- Cities are densely populated - often shanty towns
- Poor construction
- Communications systems are underdeveloped
- Emergency services are well funded
- Lots of money for researching and monitoring
- Old buildings can be retrofitted
- Buildings can be quake-proofed
LIMITING THE EFFECTS
Human built structures...
- Shorter buildings
- Strong materials - wood and steel
- Base isolators - isolating the base of the building from the earth's movements
- Building codes and regulations
However, most of these are only available for MEDC's so LEDC's use appropriate technology (technology designed with consideration of the community it is intended for)
For example: bamboo houses
PREPARING FOR EARTHQUAKES
What people can do before...
- Store bottled water and food
- Earthquake drills
- Reinforce buildings
What people can do after...
- Be prepared for aftershocks
- Stay away from damaged areas
- Search and rescue
- Monitor in case of tsunamis