Introduction to Earthquakes Flashcards
What is an earthquake?
Its the shaking of the Earth’s crust caused by rock movement.
The movement is transmitted as seismic wave through the ground as a sudden release of pressure is established.
What happens after an Earthquake has occurred?
Once the initial movement has occurred and the earthquake has happened, the rocks tend to slowly settle back into place - aftershocks.
Where do Earthquakes occur?
Anywhere but 90% occur along a plate boundary.
Some associated with old fault lines - UK.
Why do Earthquakes occur?
Due to movement along the Earth’s crust.
Plates move because of a build up of pressure.
The point where energy is released is called the focus.
Shockwaves move out from focus to the epicentre and this is where the shockwaves are the strongest.
(Human activity)
Where do shallow Earthquakes occur?
Along marine trenches where the plate subduction is taking place along the mid oceanic ridge and in the slip fault where 2 plates slide past each other.
Where do intermediate and deeper Earthquakes occur?
Subduction zones.
How can human activity cause an Earthquake?
Building of large reservoirs in which the water puts pressure on the surface rocks.
What does the sudden release of pressure create?
Strong shock waves known as seismic waves, this is the actual Earthquake.
The longer the pressure has been building up the stronger the Earthquake.
What are aftershocks?
They are Earthquakes that follow on from the main event they may last for months after.
They are generated by the Earth settling down after the disruption of the first displacement.
