Ngā Whāinga Ako 🔗
- Describe how earthquakes travel through the Earth’s rust
- Describe the characteristics of P, S and L seismic waves
Types of Earthquake Waves 🔗
- 3 different types of waves move through the Earth’s crust during an earthquake
- P, S and L waves
P Waves 🔗
- They are the first to reach the surface
- They travel the fastest (approx. $8\frac{km}{s}$)
- They squeeze and stretch the rock
S Waves 🔗
- They are the second wave to hit the surface
- They move at around $5\frac{km}{s}$
- They make the ground move up and down (and side to side)
L Waves 🔗
- Also called surface waves
- They are the last waves to hit the surface
- They do the most damage as they travel near the surface
- They move at around $4\frac{km}{s}$
Whakakite: Slinky 🔗
- Use a slink to demonstrate P and S type waves
Ngā Whāinga Ako 🔗
- How do we measure earthquakes?
Measuring Earthquakes 🔗
- To measure earthquakes we use a seismograph
- The inertia of the mass keeps the pen still as the ground moves below it, creating graph
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The energy ________ travels outwards as _____. The point in the Earth’s crust where this happens is called the _____, the point directly above the focus on the Earth’s surface is called the _________. Seismologists use ___________ to determine the magnitude and ________ of earthquakes.
Words: seismographs, focus, location, waves, epicentre, released
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- Hypocenter (focus): The point where the earthquake starts
- Epicenter: The point on the surface directly above the hypocenter
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We can see that the epicenter is the closest place on the surface to the focus. This is why the s waves get there first.
Richter Scale 🔗
- Uses numbers from 1 to 10
- Each number has 32x more energy than the previous
- It doesn’t really work because it was designed for use in Southern California for their particular geology
Mercalli Intensity Scale 🔗
- This scale uses the impact of the earthquake on the surface, rather than measuring the energy specifically