Earthquakes

Sections 6.2 and 6.3

Section 6.2 – Recording Earthquakes

Seismic waves are recorded using a seismograph

A seismograph is made of 3 separate devices

One measures up and down movement While the other 2 measure North-South

and East-West movements

Section 6.2 – Recording Earthquakes

There are 3 kinds of seismic waves Primary Waves (P waves) – move the

fastest and can travel through solids and liquids. P waves are detected first

Secondary Waves (S waves) – are slower and can only travel through solid rock. S waves are detected second

Surface Waves – are the slowest. They occur when P and S waves reach the surface and cause lots of Damage

Section 6.2 – Recording Earthquakes

It takes 3 seismographs to locate the epicenter of an earthquake

The difference in amount of time it takes the P and S waves to reach each seismograph determines how far away the earthquake occurred.

Section 6.2 – Recording Earthquakes

Magnitude is a measure of the energy released by an earthquake and it describes the amount of ground motion

The Richter scale shows how much damage is expected by the earthquake

Section 6.2 – Recording Earthquakes

Large earthquakes have a magnitude above 7

Moderate are between 6 and 7

Minor are between 2.5 and 6

Microquakes are below 2.5 and aren’t felt by people

Section 6.3 – Earthquake Damage

During severe earthquakes you would be much safer in an open field than in a city of skyscrapers

Large buildings sway and the fall over

Buildings built on loose soil are more likely to fall than those on solid ground

Section 6.3 – Earthquake Damage

A Tsunami is formed when a major earthquake happens on the ocean floor

A tsunami is a giant ocean wave

Tsunamis can also be caused by under water landslides

Section 6.3 – Earthquake Damage

Earthquakes are very hard to predict

Along some faults, scientists have identified zones of rock that are locked in to position

This is called a seismic gap.