lesson 8: earthquakes

Question 1

fault

Answer 1

a fault is a sharp break in the crustal rocks near a fault tend to move in opposite directions that creates friction but at some point, in time their movements overcome the friction as a result they slide past one another.

Question 2

epicentre

Answer 2

the surface nearest to the focus is called epicentre this place is the first one to experience the waves all natural earthquakes take place in the lithosphere the lithosphere refers to the portion of depth up to 200 kilometre from the surface of the earth an instrument called seismograph records the waves reaching the surface the waves look something like this the curve shows three distinct sections each representing different types of wave patterns we’ll get back to this pattern in a moment earthquake waves are basically of two types body waves and surface waves I need you to understand the term body waves sounds a little larger within the body right so the body.

Question 3

waves

Answer 3

• waves are generated due to the release of energy at the focus that is the epicentre and moves in all direction traveling through the body of the Earth

Question 4

primary waves

Answer 4

• Primary waves (P waves) are the first seismic waves to arrive at a seismograph12. They are the fastest seismic waves and can move through solid, liquid, or gas. P waves cause the ground to compress and expand, moving back and forth in the direction of travel. They are also called pressure waves.

Question 5

secondary waves

Answer 5

• Secondary waves (S-waves) are a type of elastic wave in seismology. They are one of the two main types of elastic body waves. S-waves move through the body of an object, unlike surface waves. They are shear waves that displace the ground perpendicular to the direction of propagation. S-waves cannot travel through liquids, only through solids.

Question 6

surface waves

Answer 6

• Surface waves travel more slowly through Earth material at the planet’s surface and are predominantly lower frequency than body waves.

Question 7

earthquake

Answer 7

The sudden release of energy when two plates that were stuck together are released, creating the energy burst. A sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the earth’s crust or volcanic action.

Question 8

epicentre (definition)

Answer 8

The epicentre is the point on the Earth’s surface directly above a hypocentre or focus, the point where an earthquake or an underground explosion originates

Question 9

focus

Answer 9

The focus of an earthquake is the point inside Earth’s crust where the earthquake originates

Question 10

seismic waves

Answer 10

They are waves of energy, created by the force of the plates moving past each other.

Question 11

what are tsunamis

Answer 11

Tsunamis are the result of a rapid displacement of water. They often occur in areas where two crustal plates are pushing against each other, forcing one plate to slide under the other. Tsunamis occur at a subduction zone, underwater volcanoes, or at transform boundary lines. The energy of the displacement pushes a large surge of water racing across the ocean at high speeds. Once the sea level gets lower, and the bottom of the wave gets closer to the seafloor, friction occurs. This pushes the top of the wave forwards, forcing the wave to gain height.