AQA Geography - seismic hazards and earthquakes

What hazards are associated with seismicity?
Earthquakes, Landslides, Shockwaves, Liquefaction, Tsunamis
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What are the physical causes of the earth shaking?
Plate tectonics; plate movements associated with stresses in the lithosphere. Stresses are overcome the rock fractures along cracks called faults sending seismic shockwaves to the surface
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What are the human causes of the earth shaking?
Fracking Mining Reservoir construction
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How are EARTHQUAKES formed?
Movements within the Earth’s crust causes stress at points of weakness, and rocks to deform. When it finally exceeds the strength of the rock, the rock fractures along a fault, often at a zone of existing weakness. This energy is released as a quake.
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the focus of an earthquake is the actual point underground where rocks break. .
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The depth of the focus can be categorized as...
shallow (up to 70 km below the surface), Intermediate (70 to 300 km), or deep (greater than 300 km)
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Seismic shockwaves
Energy released during an earthquake travels in the form of waves around the Earth.
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4 different types of waves
Primary/ pressure waves (P) Secondary / shear waves (S) Surface love (L) Rayleigh (R)
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where do the waves originate from?
They originate either from the focus or the epicentre. They move in different directions.
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P-waves (primary)
P waves are the fastest so reach the surface first. They are the first waves to be detected. They travel through the both the mantle and the core to the opposite side of the earth. They are longitudinal waves = same direction vibrations
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S-waves (secondary)
S-waves are half as fast and reach the surface next. They are high frequency but shake like a skipping rope. They can travel through the mantle but not the core.. They are transverse waves which mean the vibrations are at right angles
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P and S waves difference
Both types of seismic wave can be detected near the earthquake centre but only P-waves can be detected on the other side of the Earth. This is because P-waves can travel through solids and liquids whereas S-waves can only travel through solids.
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L waves (LOVE)
These waves are the slowest and cause most of the damage. They move from side to side. Originates from the epicentre
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R waves (Rayleigh)
These radiate from the epicentre in complicated low frequency rolling motions. The move up and down
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Earthquake Hazards
Ground shaking, Landslides and liquid fraction
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the way in which the soil liquefies during an earthquake. The water separates from the soil particles and rises to the surface.
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what are some issues caused by GROUND MOVEMENT
Buildings may collapse and kill or injure people; building design has a big effect. Underground pipes and power lines may be severed, resulting in fires and explosions, especially from gas. Ruptured water pipes can cause problems in extinguishingfire
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Liquefaction is when a solid material turns into a liquefied state due to an increase in pore water pressures as a result of ground shaking. It affects unconsolidated sediments at depths of less than 10 metres, which are saturated with water.
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PREDICTABILITY of earthquakes
Just as with volcanic eruptions, the frequency and regularity of earthquakes show no predictability.
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What are the 2 main ways to measure earthquakes?
The Mercalli scale and The Richter scale
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The Mercalli scale
The Mercalli scale measures the effects of the earthquake and runs from 1 to 12. The higher up the scale the more damage is experienced by people and building structures.
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The Richter scale
The Richter Scale measures the energy (magnitude) of an earthquake. The scale is logarithmic, which means that for every jump up the scale you get a tenfold increase in power of an earthquake.
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what are some of things that Scientists have identified can occur before an earthquake?
Micro quakes before the main tremor, Bulging of the ground, Decreasing radon gas concentrations in groundwater, Raised groundwater levels, Electrical and magnetic changes within local rock Increased argon gas content in soil Curious animal behaviour.
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Nepal earthquake magintude
7.8 magnitude
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Nepal earthquake date
- 25th April 2015
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Nepal earthquake epicenter
Epicentre 80km northwest of Kathmandu - Depth of 15km
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Nepal earthquake Death and injurged toll
Aftershocks killed 8 633 people - 3 million people made homeless - 21 000 were injured
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Nepal earthquake economic impacts
Nepal lost 25% of its GDP - US$6.6 billion needed for rebuilding - Tourism fell – it was an important part of their economy.
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Nepal earthquake social impacts
Nearly 1 million children left with no school. - 700,000 people pushed into poverty.
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Explain what makes Nepal vulnerable as far as natural hazards are concerned.
197th in world ranking of GDP per capita out of 229 countries. Poor.  Poor infrastructure governance.  Emergency services couldn’t cope.  Corrupt government. (donated monies cannot be distributed in the country unless they go directly to governmen
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Nepal earthquake environmental impacts
Springs and traditional stone spouts dried up. - Landslides increased sediment in rivers, impacting flower and fauna
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How can actions taken now reduce the impacts of any future earthquakes in Nepal?
The Nepal Risk Reduction Consortium (NRRC) is an arrangement that unites humanitarian and development partners with financial institutions in partnership with the Government of Nepal in order to reduce Nepal's vulnerability to natural disasters.
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Immediate Responses
90% of soliders were sent to worst hit areas, but efforts were hampered due to landslides. Tent cities were put up across Katmandu. Responses were criticised as slow- helicopter the day of the aftershock was brought in, to find hundreds dead.
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Long Term Responses
UK provided 30 tonnes of humanitarian aid. £50 million donated by public (UK) Uk Ghurka's sent out to respond. UK donated £73 million by government. Search teams sent out, disaster rescuers/scientists.
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Japan earthquake magintude
:8.9 and lasted 6 minutes. Aftershocks: at least 124 greater than 5 magnitude.
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Japan earthquake death and jnhured toll
Death toll:18,000 2,000 people injured
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Japan earthquake Date
11th March 2011.
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Japan earthquake Physical Impacts
Tsunami reached 6 miles inland Nuclear explosion at the Fukishima power plant damaged by floods Fires in the capital and oil refinery ablaze near Tokyo. Flooding
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Japan earthquake Secondary Impacts
Damage to infrastructure with roads, rails, power and ports were wiped. This proved difficult for relief. People missing Homelessness Houses wiped out by the tsunami. 4,700 destroyed and 50,000 damaged Economic damage to fishing ports
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Japan earthquake Tertiary Impacts
Disruption to education Local shops running out of goods Hospitals deprived of aid
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91 countries have offered aid, from blankets and food to search dogs and military transport. A British rescue team has arrived in Japan to join the search for survivors of the earthquake and tsunami. Several charities, including Save the Children UK
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Other cards in this set

Card 2


What are the physical causes of the earth shaking?


Plate tectonics; plate movements associated with stresses in the lithosphere. Stresses are overcome the rock fractures along cracks called faults sending seismic shockwaves to the surface

Card 3


What are the human causes of the earth shaking?


Preview of the front of card 3

Card 4


How are EARTHQUAKES formed?


Preview of the front of card 4

Card 5




Preview of the front of card 5
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