Understanding the background to seismic hazards Flashcards

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1
Q

What causes seismic hazards?

A

A build up of stress within rocks. When the pressure is suddenly released, parts of the surface experience an intense shaking motion that lasts for just a few seconds.

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2
Q

Where is the pressure released during a seismic hazard?

A

The focus

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3
Q

What is the epicentre?

A

The point immediately above the focus on the crust

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4
Q

What is defined as a shallow focus?

A

0-70km deep

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5
Q

What is defined as a intermediate focus?

A

70-300km deep

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6
Q

What is defined as a deep focus?

A

300-700km deep

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7
Q

How is the magnitude of an earthquake measured?

A

The Richter scale, a logarithmic scale

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8
Q

What is more commonly used to measure earthquakes?

A

MMS - moment magnitude scale

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9
Q

What does the MMS measure?

A

Identifies the energy released

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10
Q

What was the Mercalli scale?

A

Measures intensity

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11
Q

How do we predict seismic hazards?

A

Monitor groundwater levels
Measure local magnetic fields
Areas can be mapped on the basis of geological information and studies made into ground stability - predict the impact of an earthquake - product hazard zine map - used by national planners

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12
Q

How do we prevent earthquakes?

A

It is pretty much impossible, however there have been studies into lubricating the movement of plates, to stop ‘sticking’ then releasing

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13
Q

How do we protect ourselves from seismic hazards?

A

In USA, FEMA follows certain objectives: educate people of EQ effects and risk, improve construction, encourage planning policies

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14
Q

How can buildings be designed to be aseismic?

A

Putting a large concrete weight on the top of the building which will move, with the aid of a computer programme, in the opposite direction to the EQ to counteract stress
Large rubber shock absorbers in the foundations
Adding cross-bracing to the structure to hold it together

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15
Q

How does education protect us from earthquakes?

A

Instruction can be issued on how to secure homes, appliances, and heavy furniture, and assembling ‘EQ kits’.

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16
Q

How does fire prevention protect us from earthquakes?

A

‘Smart metres’ have been developed that can cut off the gas if an EQ occurs - reducing fires

17
Q

How does land-use planning protect us from earthquakes?

A

Certain types of buildings should be put in areas of low risk, such as schools and hospitals

18
Q

How does insurance protect us from earthquakes?

A

Richer areas, people are urged to take out insurance to cover their losses - can be expensive