KS3 Geography - Tectonic Hazards: Earthquakes

In this page, you will find information on:

• What is an earthquake?
• What is the focus and epicentre of an earthquake?
• What are the seismic waves of an earthquake?
• Animation of earthquakes
• A detailed earthquake presentation
• Impact of earthquakes
• How to measure earthquakes?
• Earthquake safety
• Can earthquakes be predicted?
• Case studies of destructive earthquakes
• Earthquke simulation activity
• Seismic waves activity
• Seismic waves simulation game
• Interactive game: how to locate an earthquake?
• Quiz on earthquakes
• Earthquakes Q&A game
• Interactive zone: experience the Haiti earthquake

   An earthquake is the shaking and vibration of the Earth's crust due to movement of the Earth's plates (plate tectonics). Earthquakes can happen along any type of plate boundary.

   Earthquakes occur when tension is released from inside the crust. Plates do not always move smoothly alongside each other and sometimes get stuck. When this happens pressure builds up. When this pressure is eventually released, an earthquake tends to occur.

   The effects of an earthquake can be devastating - they can destroy settlements, change landscapes, and cause many deaths.

   The point inside the crust where the pressure is released is called the focus (or hypocenter). The point on the Earth's surface above the focus is called the epicentre.

   Earthquake energy is released in seismic waves. These waves spread out from the focus. The waves are felt most strongly at the epicentre, becoming less strong as they travel further away. The most severe damage caused by an earthquake will happen close to the epicentre.

   Earthquake energy is released in seismic waves. These waves spread out from the focus. The waves are felt most strongly at the epicentre, becoming less strong as they travel further away.

Properties of seismic waves

P-waves are longitudinal waves like sound waves, and s-waves are transverse waves like light waves.

The most severe damage caused by an earthquake will happen close to the epicentre.

   Scientists have tried many different ways of predicting earthquakes, but none have been successful. One basic idea behind quake prediction is that faults send out subtle but detectable warnings before they slip. Scientists have looked at a host of potential warning signals, or "precursors," including foreshocks, weird animal behavior, and changes in the water table, stream flow, well levels, and patterns of electrical currents in the ground. However, on any particular fault, scientists know there will be another earthquake sometime in the future, but they have no way of telling when it will happen.

You need to learn the causes and consequence of some major earthquakes from case studies. Click the images or links below to go to the case studies.

1989 San Francisco Earthquake

   Earthquakes can destroy settlements and kill many people. Effects of earthquakes are often classified as primary and secondary impacts. Primary effects occur as a direct result of the ground shaking, eg buildings collapsing. Secondary effects occur as a result of the primary effects, eg tsunamis or fires due to ruptured gas mains. It is also possible to classify the impacts of an earthquake by taking the following factors into account:

   The size of an earthquake is measured on a Richter scale 0-10 of magnitude using an instrument called a "seismograph". Seismographs are basically pens suspended over a paper-covered rotating drum. When the earth trembles the pen makes a larger squiggle on the drum, allowing the size of the shaking to be measured. Each whole number on the Richter scale represents an earthquake 30 times larger than the number below it. Earthquakes that measure less than 3.0 are not usually felt, while one of 5.0 produces the same amount of energy as the Hiroshima atomic bomb. Earthquakes measuring around 7 or 8 on the Richter scale can be devastating. The largest recorded quake happened in Chile in 1960 and measured 9.5.

(Click a box above to learn more! Bigger version here)

BEFORE AN EARTHQUAKE:

• Have a disaster plan.
• Choose a safe place in every room. It’s best to get under a sturdy piece of furniture like a table or a desk where nothing can fall on you.
• Practice DROP, COVER AND HOLD ON! Drop under something sturdy, hold on, and protect your eyes by pressing your face against your arm.
• If you live in an earthquake prone area, bolt tall furniture to the wall and install strong latches to cupboards.
• Prepare a disaster supplies kit for your home and car. Include a first aid kit, canned food and a can opener, bottled water, battery-operated radio, flashlight, protective clothing and written instructions on how to turn off electricity, gas, and water.

DURING AN EARTHQUAKE:

• DROP, COVER AND HOLD ON!
• Stay indoors until the shaking stops.
• Stay away from windows.
• If you’re in bed, hold on and stay there, protecting your head with a pillow.
• If you’re outdoors, find a clear spot away from buildings, trees and power lines. Then, drop to the ground.
• If you’re in a car, slow down and drive to a safe place. Stay in the car until the shaking stops.

AFTER THE SHAKING STOPS:

• Check for injuries.
• Inspect your home for damage.
• Eliminate fire hazards, so turn off the gas if you think its leaking.
• Expect aftershocks. Each time you feel one, DROP, COVER AND HOLD ON.

Why do earthquakes occur? Learn about them in this activity!

Understand how seismic waves work by playing the following activity!

Play the following game to understand more about seismic waves!

Are you ready to answer the questions about earhquakes?

zondle - games to support learning