Earthquakes Flashcards
What is an earthquake?
Movement within the Earth’s crust caused by stress which is released at points of weakness. This stored energy is suddenly released as an earthquake. Intense vibrations, or seismic waves spread out from the initial point of rupture, the focus, like ripples on a pond. The waves make the earth shake and can travel large distances in all directions.
What is the epicentre?
the point of the earth’s surface above the focus of the earthquake.
What is the focus?
The point of origin of an earthquake.
What are faults?
an extended break in a rock formation.
What are the differences in earthquakes at different plate boundaries?
At constructive plate boundaries they have a small magnitude with a shallow focus.
At destructive plate boundaries they have a large magnitude, with a deeper focus because of the bigger surface area so there is greater pressure.
At collision plate boundaries stress releases as earthquakes along lines of weaknesses (faults).
What is an ‘earthquake storm’?
When one earthquake leads to another along a fault line.
It increases the predictability of earthquakes - Istanbul at the end of the north anatolian fault has a big earthquake roughly every thirty years.
What are seismic waves? What are the two catagories?
Seismic waves are vibrations from an earthquake. They are categorised a P or S waves and travel through the Earth in different waves and different speeds.
What are P waves? What are S waves?
P - waves (primary) arrive at detector first and are in longitudinal waves; The vibrations are along the same direction as the direction of travel.
S - waves (secondary) arrive at detector second and are
transverse waves; the vibrations are at a right angle to the direction of travel.
How can earthquakes be measured?
The Richter scale, the Mercalli scale, and Moment Magnitude scale.
