Seismic hazards

Question 1

What is an earthquake?

Answer 1

As the crust is mobile there tends to be a slow build up of stress within the rocks. The rocks then snag on each other and break and move.Then a sudden release of seismic waves means that parts of the surface then experience intense shaking.

Question 2

Which focus tends to cause the greatest damage

Answer 2

shallow focus (0- 70km deep)

Question 3

Where do most earthquakes occur

Answer 3

Along plate boundaries but some are away from plate boundaries and caused by human activity eg. fracking or stress on old fault lines

Question 4

What is the epicentre of an earthquake

Answer 4

The point directly above the focus above ground which Is the most hazardous location

Question 5

What is the focus of the earthquake

Answer 5

The point within the crust where the plates give way. The place where seismic waves travel out of

Question 6

What are seismic waves measured on

Answer 6

A seismograph uses weight pen and paper to draw ripples on a graph
P waves will be recorded first

Question 7

What are primary waves?

Answer 7

The fastest 5.5km / hr and vibrate in the direction of travel.
They are compressed waves
They travel through core and mantle
LOOK LIKE A SLINKY BACK AND FORWARD

Question 8

What are secondary waves?

Answer 8

Much shower half as fast and vibrate at right angles in direction of travel
Transverse waves
Travel through mantle but not core
RIPPLE UP AND DOWN IN AN S SHAPE

Question 9

What are surface waves?

Answer 9

Love waves:
one large ripple sideways at a time
causes ground to move sideways

Rayleigh waves:
A larger version of S ripple
cause the ground to move up and down

Question 10

What type of earthquakes do divergent plates cause?

Answer 10

Shallow quakes that occur frequently but low magnitude

Question 11

What type of earthquakes do convergent oceanic crust cause?

Answer 11

Major hazards infrequent and high magnitude

Question 12

What type of earthquakes do convergent continental crust cause?

Answer 12

Shallow earthquakes created from pressure

Question 13

What type of earthquakes do conservative plates cause?

Answer 13

Shallow depth quakes

Question 14

What are primary effects of earthquakes?

Answer 14

Ground shaking and ground rupture

Question 15

What are secondary effects of earthquakes?

Answer 15

Soil liquefaction
Landslides
Tsunamis
Fires
Effects on people and environment

Question 16

What is soil liquefaction?

Answer 16

Soils with a high water content lose their mechanical strength and behave like a fluid

Question 17

What are landslides?

Answer 17

Slope failure

Question 18

What are tsunamis?

Answer 18

Giant sea waves generated by shallow focus underwater earthquakes involving movements of the sea bed
They travel at over 700km per hour

Question 19

What do tsunami waves look like?

Answer 19

They have a long wavelength and a low wave height but they increase in height when they reach shallow water

Question 20

What are methods of prevention

Answer 20

Hazard resistant structures
Education 
Fire prevention 
Emergency services
Land use planning
Insurance
Aid 
Tsunami protection

Question 21

What are hazard resistant structures?

Answer 21

Large concrete weight on top of the building which will move in opposite direction to the force of the earthquake
Putting large rubber shock absorbers in the foundations
Adding cross bracing to the structure to hold it together

Question 22

What are methods of education?

Answer 22

Children will have earthquake drills at school

People should have earthquake supplies ready just in case

Question 23

What are methods of fire prevention?

Answer 23

smart meters developed to cut off gas