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Earthquakes

Earthquakes

 

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Objective for today’s lesson is to discover:

  1. What is an earthquake?

  2. How do we measure earthquakes?

  3. What causes an earthquake?

  4. What is the focus and epicentre?

  5. Earthquakes in LICs – Case study Haiti 2010

 

What is an earthquake?

Watch the YouTube clip and then explain what is an earthquake.

An earthquake is a sudden and brief period of intense ground-shaking.

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.

How do we measure earthquakes?

kew 4 measure _47413605_richter_earthquake4_466_2

The figures above measure an earthquake in terms of the energy released.

The power of an earthquake is measured using a seismometer. A seismometer detects the vibrations caused by an earthquake. It plots these vibrations on a seismograph.

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The strength, or magnitude, of an earthquake is measured using the Richter scale. The Richter scale is numbered 0-10.

World’s Twelve Largest Earthquakes

Includes all measured earthquakes since 1900

Magnitude
Location
Date
9.5
Chile
05/22/1960
9.2
Alaska
03/28/1964
9.1
Off the coast of Northern Sumatra
12/26/2004
9.0
Honshu, Japan
03/11/2011
9.0
Kamchatka
11/04/1952
8.8
Off the coast of Chile
02/27/2010
8.8
Off the coast of Ecuador
01/31/1906
8.7
Rat Islands, Alaska
02/04/1965
8.6
Northern Sumatra
03/28/2005
8.6
Tibet
08/15/1950
8.6
Off the coast of Nortern Sumatra
04/11/2012
8.6
Andreanof Islands, Alaska
03/09/1957
Data from the United States Geological Survey

Causes of an earthquake:

Earthquakes are found along plate boundaries (areas where two or more plate meet) and there are three plate boundaries where earthquakes are very common.

  • Collision plate boundary
  • Destructive plate boundary
  • Conservative plate boundary

The Oreo test

SONY DSC

Collision plate boundary

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A collision or convergent plate boundary happens when two continental plates collide.  You get big earthquakes at collision boundaries because there is a massive build up of friction and pressure e.g. Nepal (2015).

Destructive plate boundary – subduction zones

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A destructive or convergent plate boundary is when oceanic and continental crust collide. The denser oceanic crust is forced (subducted) under the continental plate. Big earthquakes are found at destructive plate boundaries because of the build up of pressure between the two plates e.g. Chile (1960 – 9.5 on the Richter scale)

Conservative plate boundary

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A conservative or transform boundary happens when two continental plates move alongside each other. There is a huge build up of pressure between the two plates so massive earthquakes do occur e.g. Haiti (2010)

What is the focus and epicentre?

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Epicenter-The point on the Earth’s surface located directly above the focus of an earthquake.

Focus-The location where the earthquake begins. The ground ruptures at this spot, then seismic waves radiate outward in all directions.

Discussion: How can the focus and epicentre impact on the severity of an earthquake?

Earthquakes in Low Income Countries (LICs)

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The figures above measure an earthquake in terms of the energy released.

Kew 13 Iran Bam 300512bam-earthquakecredit-james-jackson

The figures above measure an earthquake in terms of the energy released.

 

 

 

 

 

 

A countries level of development (HIC or LIC) will determine how severely the effect of an earthquake will be on that particular area. This is due to the fact that HICs are more likely to have the resources and technology for monitoring, prediction and responses to deal with a natural hazard like an earthquake. LICs, on the other hand, have many of the following issues:

  • Communication systems may be underdeveloped, so the population may not be well educated about what to do in the event of a volcanic eruption or an earthquake.
  • Construction standards tend to be poor in LEDCs. Homes and other buildings may suffer serious damage when a disaster occurs.
  • Buildings collapsing can cause high death tolls.
  • Evacuation and other emergency plans can be difficult to put into action due to limited funds and resources.
  • Clearing up can be difficult. There may not be enough money to rebuild homes quickly and safely. Many people could be forced to live in emergency housing or refugee camps.

Case study Haiti

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Quick Facts

Place – Haiti (LIC)

Date – 12 January 2010

Size – 7 on the Richter Scale

Cause – Conservative plate boundary

Preparation:

  • No local disaster planning was in place.
  • Buildings were not designed to be earthquake resistant.
  • Communications were poor. There were badly constructed roads and ports.

Effects:

  • Around 250 000 deaths, mostly from collapsed buildings.
  • Over 300 000 people were
  • Large areas of the capital city were destroyed – which was densely populated.
  • 5 million People were made homeless.
  • Water pipelines and electricity lines were broken cutting off supply.
  • The airport and the harbour were badly damagedstopping vital aid from getting in and reaching the needy.

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HAITI NEWSPAPER ARTICLE

Click on the link HAITI – FACT FILE – EARTHQUAKE study the information carefully

Use the framework haiti-newspaper-format  to create a newspaper article about the Haiti earthquake.

The link  is an example_of_newspaper_article

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Do you think that you can remember what we did today?

Try these questions:

  1. Can you tell the person sitting next to you what an earthquake is?

  2. Write down what we use to measure the magnitude of an earthquake.

  3. Can you remember at least one plate boundary where earthquakes are found – remember the Oreo test.

  4. Where does an earthquake originate  – epicentre or earthquake?

  5. Why was the death toll so high in Haiti after the earthquake?

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