Earthquakes Flashcards

1
Q

What is an earthquake (EQ)?

A

the shaking of the Earth’s crust in the release of pressure

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2
Q

What 2 reasons might we get EQs in the UK?

A

old fault lines being reactivated
human activity such as fracking

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3
Q

What are seismic waves?

A

vibrations from earthquakes that travel through the Earth

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4
Q

What waves are first to arrive after an EQ?

A

P-waves

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5
Q

What are faster, S-waves or P-waves?

A

P-waves

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6
Q

What surface waves have an orbit that is similar to ocean waves?

A

Rayleigh Waves

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7
Q

What is meant by an EQs magnitude?

A

the quantitative measure of energy released at the source of an earthquake

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8
Q

What 2 ways measure the magnitude of an EQ?

A

the Richter Scale
the Moment Magnitude Scale (MMS)

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9
Q

What does the Mercalli scale measure?

A

the intensity of EQs

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10
Q

What are 2 primary hazards of EQs?

A
  • ground shaking
  • ground rupturing
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11
Q

Give 2 factors that can impact the severity of ground shaking in an EQ

A
  • local geology
  • depth
  • magnitude
  • distance from epicentre
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12
Q

What is soil liquefaction?

A

violently shaken soils with high water content lose their mechanical strength and start to behave like a fluid

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13
Q

What are 4 secondary impacts of EQs?

A
  • tsunamis
  • fires
  • soil liquefaction
  • landslides/avalanches
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14
Q

Briefly outline how tsunamis are formed

A
  • destructive margin
  • over-riding plate becomes distorted
  • plate rebounds, displacing a large amount of water
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15
Q

What are features of a tsunami when out at sea?

A
  • very fast (up to 700km/hr)
  • very short in height (>1m)
  • very long wavelength (up to 100km)
  • calm conditions
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16
Q

Give 3 features of EQ resistant buildings

A
  • rolling, concrete weights
  • cross-bracing
  • shock absorbers
17
Q

What are some disadvantages to an EWS?

A

people might not always respond, only a short duration beforehand

18
Q

How might adapting land-use limit destruction caused by EQs?

A
  • high risk areas- parks, open spaces etc.
  • lower risk areas- schools, hospitals, big buildings
  • build in open spaces for evacuation
19
Q

Why might preparedness strategies not be used against EQs?

A
  • financial issues
  • takes long-term education and depends on priorities
20
Q

What could be done to prevent soil liquefaction?

A

soil stabilisation (using gravel columns)

21
Q

Which waves are the most destructive?

A

love waves