Earthquakes 3 3 0 Earthquakes Learning Intentions You

Earthquakes 3

3. 0 Earthquakes Learning Intentions You will be able to: § Explain how an earthquake occurs using key terminology and diagrams. § Describe the occurrence and distribution of earthquakes. § Describe the economic and social impacts of earthquakes in Chile and Nepal. 3

3. 1 Studying Earthquakes An earthquake is the sudden shaking of the earth caused by the movement of the earth’s crust. Most earthquakes occur along the edges of large plates, where they collide or slide past each other. Seismologists are scientists who study earthquakes. Earthquakes 3

3. 2 Earthquakes Focus: The place where an earthquake begins beneath the earth’s surface. Shock waves: Also called ‘seismic waves’. These spread out in circles from the focus. Epicentre: The point on the earth’s surface that is directly above the focus of the earthquake. Fault: A large crack in the earth’s crust. 3

3. 1 Studying Earthquakes The San Andreas Fault A large crack in the earth’s crust that marks a plate boundary Located in California Slow-moving North American plate Faster-moving Pacific plate When the plates touch, they can lock together An earthquake occurs when one plate suddenly jumps forward, slips or breaks Earthquakes 3

3. 3 Tsunami Waves Earthquakes 3 How a tsunami happens An undersea earthquake disturbs the seabed and causes power waves to move out quickly in all directions. A tsunami can devastate low-lying areas. The waves become much higher as they approach shallow water near the coast.

3. 4 Measuring Earthquakes Seismograph Earthquakes 3 The instrument used to measure and record an earthquake and how long it lasted. Phone apps today allow you to carry your own seismograph in your pocket! Richter scale The original scale used to measure the magnitude (strength) of an earthquake. This scale goes from 1 to 8. Each one-unit increase means that the earthquake is ten times more powerful than it was at the previous unit. Moment magnitude scale Used to measure the magnitude of earthquakes. It replaced the Richter scale because it is more reliable for larger earthquakes. The scale goes from 1 to 10.

3. 5 Economic and Social Impacts Nepal Earthquake 2015 25 April 2015 7. 8 on the moment magnitude scale 80 km away from Kathmandu 15 km below the surface Two large aftershocks Earthquakes 3

3. 5 Economic and Social Impacts Earthquakes 3 Nepal Earthquake 2015 Social impact Almost 9, 000 people died, and 17, 000 were injured Electricity, water supplies, sewage systems and communication networks were all affected 90% of clinics and schools in some areas were left unusable An avalanche on Mount Everest killed 19 people Landslides affected villages and parts of Kathmandu Economic impact Cost of damage was $9 billion 1 million children were left without schools to attend 3. 7 million people needed emergency aid

3. 5 Economic and Social Impacts Chile Earthquake 2010 10 February 2010 8. 8 on the moment magnitude scale 300 km away from the capital Santiago 35 km below the Pacific Ocean Hundreds of aftershocks Triggered a tsunami wave Earthquakes 3

3. 5 Economic and Social Impacts Earthquakes 3 Chile Earthquake 2010 Social impact Over 500 people died, 12, 000 were injured Twelve million people felt strong tremors Water, electricity and communication systems were badly affected Roads were blocked and bridges collapsed Coastal towns were hit by tsunami waves Economic impact Cost of damage was $30 billion 441, 000 houses were severely damaged or destroyed Limited food availability led to looting Tourism industry hit by cancellations

Earthquakes DEADLY EARTHQUAKE STRIKES CHILE A massive 8. 8 earthquake has struck Chile leaving hundreds dead and the search continues for survivors. 3

3. 6 Reducing Earthquake Damage We can try to reduce the damage caused by earthquakes by: Predicting when an earthquake might occur Planning for earthquakes Constructing earthquakesafe buildings Earthquakes 3

Earthquakes Video: Pacific Tsunami Warning Centre 3