Seismic Hazadds

Question 1

What is the epicentre in an earthquake

Answer 1

The point directly above the focus on the surface

Question 2

What is the focus in an earthquake

Answer 2

Where the earthquake originates in the earth’s crust

Question 3

What does being closer to the epicentre mean for buildings and people

Answer 3

Closer to epicentre - more damage

Question 4

What are the steps to seismic waves

Answer 4

Pressure builds at the point where two points meet
Sudden release due to rock failure creates waves
These waves cause the groud to shake
This causes earthquakes

Question 5

What are the 4 seismic wave types

Answer 5

P wave
S wave
Rayleigh wave
Love wave

Question 6

What sre the features of a p wave

Answer 6

Short pulse of energy moving the groud forwards and backwards
Fastest moving
Least damaging

Question 7

Ehay sre the features of an s wave

Answer 7

S waves move the group and down
More damaging than p waves
Slightly slower than p waves

Question 8

What are the features of a Rayleigh wave

Answer 8

Rayleigh waves go up and down
Slower than s waves
Damaging to buildings because they are slower

Question 9

What are the features of a love wave

Answer 9

Move the ground sideways
Relatively slow
The most damaging

Question 10

How are tsunamis formed (simple)

Answer 10

Most commonly by destructive plate boundaries in the ocean which creates earthquakes when the overriding plate snaps back
Pressure is released - rapid movement of ocean floor displaces a column of water
Series of small heighted waves travel across open ocean
Energy compresses as it reaches the shore and small waves become one big wave -water retreats from shoreline

Question 11

What is liquefsction

Answer 11

Liquefaction- mixing of sand/soil and groundwater
When water and soil mix the ground becomes very soft
If liquefaction causes some buildings to tip or sink
The ground firms up as groundwater retreats after an earthquake leaving the buildings ajar

Question 12

What are landslides and how do they occur

Answer 12

Grounshaking because earthquakes destabilises cliffs and causes landslides
Heavy rain or unconsolidated rock make this more likely

Question 13

What are three ways to predict earthquakes

Answer 13

Seismic records
Radon gas emissions
Remote sensing

Question 14

How can looking ast seismic records help predict earthquakes

Answer 14

Seismologists are able to see if earthquakes are more likely to strike by calculating probabilities and forecasts

Question 15

How can remote sensing help us predict earthquakes

Answer 15

Often an increase in surface and near surface temperature before an earthquake - ir satellite can record thermal anomalies
Sometimes gas and aerosol content change before an earthquake

Question 16

How can remote sensing help us predict earthquakes

Answer 16

Often an increase in surface and near surface temperature before an earthquake - ir satellite can record thermal anomalies
Sometimes gas and aerosol content change before an earthquake

Question 17

How can radon gas emissions help us predict an earthquake

Answer 17

Radon is released from cavities and cracks as the earth’s crust is strained prior to the sudden slip of an earthquake

Question 18

What are some primary effects of an earthquake

Answer 18

Liquefaction of saturated soils
Panic , fear and hunger
Schools destroyed
Damage to power stations
Buildings/bridges , power lines , water mains , gas mains and sewers collapse -
Immediate deaths from injuries such as crushing

Question 19

What are some secondary effects of an earthquake

Answer 19

Bodies not disposed of properly spread diseases like cholera
Fire caused by broken gas pipes are difficult to put out
Flooding from blocked rivers create “quake lakes”
Looting and civil disorder
Power cuts restrict immediate medical care
Education suspended for immediate future
Slope failures setting if landslides and avalanches

Question 20

What are some long term effects of an earthquake

Answer 20

Reconstruction of power stations may take long as its very expensive
Long term “lost generation “ ti develop local / regional economy
Loss of farmland and food production
Higher unemployment as businesses might not recover
Trauma and grief may take years to recover
Problems restoring trust in neighbours and civil authorities

Question 21

What is the Mercali scale and what is it useful for

Answer 21

A subjective view of an earthquakes effects and useful for judging the necessary response to an earthquake

Question 22

What is the richer scale

Answer 22

A scale which measures the ground deformation and energy release caused by and earthquake

Question 23

Why do scientists use the richer scale and not the mercali scale

Answer 23

The richer scale is completely unbiased while the mercali scale may change from person to person