Leaving Certificate Geography Unit 1 4 Earthquakes 30092020

Leaving Certificate Geography Unit 1. 4 : Earthquakes 30/09/2020 Mr. Mc. Mahon Mr. C. Mc. Mahon 1

Learning Outcomes • You will learn…. • What an earthquake is. • Why they occur. • How their global pattern is explained by the location of fault lines. 30/09/2020 Mr. C. Mc. Mahon • How earthquake zones are located and measured. • How they are predicted. • How earthquakes impact upon the landscape and human populations. 2

Earthquakes-The Past Ten Years Year Place Richter Scale Casualties 2004 Sumatra Indian Ocean 9. 1 230, 000 2008 Sichuan Province 7. 9 China 87, 587 2005 Pakistan 7. 6 86, 000 2010 Japan 6. 8 12, 690 (14, 000 unaccounted for) 30/09/2020 Mr. C. Mc. Mahon 3

What is an Earthquake ? Scarp 30/09/2020 Damage Decreases From Epicentre Mr. C. Mc. Mahon 4

What Causes Earthquakes? • The plates of the crust are constantly moving. • Sometimes plates jam or stick together. • This creates a build up of energy when one or both plates slip releasing seismic waves that can violently shake the surface above. http: //www. youtube. com/watch? v=P 53 OJd_lxew 30/09/2020 Mr. C. Mc. Mahon 5

Key Concepts 30/09/2020 New Zealand • Focus: The point where an earthquake begins in earth’s crust. Earthquakes can be shallow or deep focus. • Epicentre: The point on the surface that is the worst affected by a quake. Damage lessens the further one moves from the epicentre. Earthquake 2011 Mr. C. Mc. Mahon 6

The Global Distribution of Earthquakes 30/09/2020 Mr. C. Mc. Mahon 7

Location of Earthquakes • Earthquakes do no occur randomly. • Their location is based on plate boundaries. • Earthquakes occur at convergent, divergent and transform boundaries. 30/09/2020 Mr. C. Mc. Mahon 8

• The Subduction zone of Japan is the most earthquake prone area in the world. • Transform Fault. California USA. • Rifting: East Africa • Divergent: Mid Atlantic Ridge. • Convergent: Columbia -Chile 30/09/2020 Mr. C. Mc. Mahon 9

Seismic waves • Primary (P) waves: Fast waves that compress then expand molten material • http: //www. youtube. com/watch? v=_YLj. Iv. JXhpg 30/09/2020 Mr. C. Mc. Mahon 10

• Secondary (S) waves are slow as they have to travel through solid rock. 30/09/2020 Mr. C. Mc. Mahon 11

Earthquake Waves 30/09/2020 Mr. C. Mc. Mahon 12

• Surface Waves: The slowest waves that expend their energy on the surface causing anything on it to move up and down. • Principle. Energy from waves is absorbed by material as it travels through them. Thus the father a wave travels the more energy they expend. 30/09/2020 Mr. C. Mc. Mahon 13

Measuring Earthquakes • The Seismograph • Three are needed for a full set of data • Horizontal measuring waves North-South • Horizontal- East to West. • Vertical Movement 30/09/2020 Mr. C. Mc. Mahon 14

The Richter Scale • Logarithmic Scale. • Each unit is 10 times the wave activity of the previous for example a force 8 is 10 times greater than a force 7. • The force is measured at a greater rate of 30. http: //www. youtube. com/watch? v=1 qbg 30/09/2020 Mr. C. Mc. Mahon 7 orb 1 lc 15

Predicting Earthquakes • Earthquake zones are identified. • Predictions based on timeframes. • Seismologist Identify seismic gaps- points between plates where earthquakes are likely to begin. 30/09/2020 Mr. C. Mc. Mahon 16

Early Warning Systems • Early Warning systems based on modern communication systems are being developed. • Monitoring animal behaviour. 30/09/2020 Mr. C. Mc. Mahon 17

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Destruction by Earthquakes • Destruction by earthquakes depends on the following. • The depth of the focus • The population density around the epicentre. • Economic development and the standard of buildings. • Overlying Topography 30/09/2020 Mr. C. Mc. Mahon 19

Soil Liquefaction • Liquefaction is the process of soil, clay and sand turning into a sludge. • During an earthquake ground water mixes with the soil types to produce a material like quicksand. • This undermines the foundations of bridges, roads, dams etc…. • Consequences ? 30/09/2020 Mr. C. Mc. Mahon 20

Other Dangers • Falling Debris • Flooding • Burst gas and sewage mains. • Spread of disease • Disruption to emergency services • Tsunamis 30/09/2020 Mr. C. Mc. Mahon 21

Tsunami • Giant waves that are generated when an earthquake occurs on the sea floor. • See Indian ocean Earthquake - Tusnami animation Wikipedia 30/09/2020 Mr. C. Mc. Mahon 22

Limiting Earthquake Damage • Retro- fitting of Old Buildings. • The development of advanced warning systems • Tapered frames to increase a buildings frames integrity • The use of shock absorbers in a buildings columns and foundations. 30/09/2020 Mr. C. Mc. Mahon 23

Case Study: The Haiti Earthquake • Tuesday 12 th January 2010. • Measured 7. 0 Richter Scale • Focus at 13 KM • Epicentre 13 KM from the capital Port Au Prince www. bigpicture@boston. com. Haitiearthquake 30/09/2020 Mr. C. Mc. Mahon 24

Haitian Earthquake Map 30/09/2020 http: //www. youtube. com/watch? v=1 Iz. EYHet. FUE Mr. C. Mc. Mahon 25

Case Study: The Japan Earthquake • Struck on March 11 th 2010 • Richter Scale 9. 0 • Epicentre 60 KM from the coast triggered Giant Tsunami • Over 12, 690 dead and 14, 000 unaccounted for. http: //www. youtube. com/watch? v=3 Uq 2 h. A 2 -9 oc 30/09/2020 Mr. C. Mc. Mahon 26

http: //www. youtube. com/watch? v=h. Oe 8 PMo. Kd. I 8 Japan Earthquake Map 30/09/2020 Mr. C. Mc. Mahon 27

Key Concepts • • • Earthquake Focus Epicentre Seismology Seismograph Richter scale Magnitude P Waves Q Waves S Waves 30/09/2020 • Earthquake Prediction • Early Warning Systems • Scarp • Tsunami • Tremor • Aftershocks Mr. C. Mc. Mahon 28