Module 1.5 - Earthquakes Flashcards
what is an epicentre
point on earths surface directly above the focus point of an earthquake
what is a focus
where pressure is released
what is a fault line
boundary between two plates
what is the richter scale
used to calculate magnitude of earthquake (+1 = x10)
what is an earthquake
rapid movement of the ground caused by rapid release of energy as the tectonic plates move
What causes an earthquake
earths tectonic plates are held together by friction, when this force of friction is overtaken by the force of the crust the pkates suddenly move. this jolt creates waves of energy, the ground and water shakes the the energy waves pass through them
what is a seismic wave
vibrations that travel through earth caused by earthquakes
in what direction do primary waves shake (longitudinal or transverse)
longitudinal (back and forth)
at what speed do p waves travel , what medium can p waves travel through and what level of destruction is created
8km/s (fasted wave type)
travels through liquid and solid
level of destruction: low
in what direction do secondary waves shake (longitudinal or transverse)
transversal (up and down - opposite to way the wave hits)
at what speed do s waves travel , what medium can p waves travel through and what level of destruction is created
4.5km/s (second fastest - comes in after p wave)
only travels through solid
level of destruction : Medium
in what direction do surface waves shake
in circular motion
at what speed do surface waves travel , what medium can p waves travel through and what level of destruction is created
no speed quoted
travels only through the the very top of earths surface
level of destruction HIGH
why do waves follow a curved path
shock waves spread in al directions from focus
why do waves suddenly change directions
shock waves are refracted off different substances
How do S waves relate to the structure of the earth
s waves can’t go through liquid meaning that the waves cannot penetrate the cores outer liquid
Explain australias intra plate earthquakes
australia is not on a plate boundary but when the indo australian plate is being pushed North and is colliding with the eurasian, Phillipine and pacific plates we feel earthquakes because eventually a build up of stress inside our plate is let out and thats how we feel it.
what is a tsunami
long high waves caused by sudden movement of the ocean floor due to earthquakes, landslides and earthquakes
what causes tsunamis?
caused by undersea earthquakes where a plate boundary rises or falls displacing the water above and creating fast ripple waves that travel at 800km/s. As the floor becomes shallower the wave slows down and whilst doing so the fast ripples behind them collide and become larger and inundate the land.
What is the effect of tsunamis
trough sucks the tude back in and 5 mins later a series of gigantic waves come
