1) Convection currents in the Earth’s core cause the tectonic plates to move- FALSE

2) A magnitude 6 earthquake is twice the size of a magnitude 3 earthquake

- FALSE

3) S waves travel faster than P waves- FALSE

4) Shield volcanoes have viscous magma and steep sides - FALSE

Do now: Just write TRUE or FALSE to the following:

Thursday, April 20, 2023

Today’s Learning

1) Describe how earthquakes travel through the earth’s crust

2) Describe the characteristics of P, S and L seismic waves

3) Locate the epicentre of an earthquake

Thursday, April 20, 2023

Types of Waves

3 different waves move through rock like ripples in a pond.

Video clip: seismic waves

Types of Waves

P-Waves or primary waves are the first waves to hit as they move the fastest (8km/s). They squeeze and stretch the rock.

Types of Waves

The next waves to hit are the secondary waves (S-Waves). These waves move at 5km/s and make the ground shake up and down as well as from side to side.

Types of Waves

Traveling at 4km/s are the last waves to hit, the L-Waves. These waves do the most damage as they travel near the surface of the crust.

Types of Waves

All three together.

Now do the worksheet on P, S, L waves

Features P- Waves S - Waves L - Waves

Full Name Primary Secondary Long

Action Push / pull Up / down / sideways

Rolling

Travelling Speed

Speed 5 - 13 km/s

Speed 3 - 8 km/s

Speed 3 - 4 km/s

Arrival First Second Third

Damage Level Minor Moderate Major

In Water Pass through Absorbed Pass through

Location In crust In crust Surface only

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.

seismographs focus location

waves epicentre released

released

wavesfocus

epicentre seismographslocation

Locating the Epicentre

It takes data from at least 3 seismographs to locate the epicentre.

Here is the data from 3 stations.Seismic Station Distance (km)

Auckland 4000

Hawaii 4000

Fiji 3000

An earthquake occurred approximately 4000 km from Auckland, 4000 km from Hawaii and 3000 km from Fiji. Find the epicentre.

0 km 4000 km

2000 km

Epicentre