Hazards Flashcards

1
Q

What is a natural hazard?

A

a natural process that could disrupt humans
e.g. could cause death, injury, damage property

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a natural disaster?

A

a natural hazard that has happened

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How do we class something as a hazard?

A

To be classed as a hazard, it needs to pose a threat to humans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a seismic hazard?

A

the hazard associated with potential earthquakes in particular areas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the different hazards/consequences associated with earthquakes? (seismic hazards)

A

Tsunamis
Subsidence
Liquefaction
Ground shaking
Landslides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the process of an earthquake?

A
  1. Movement of bedrock either side of a fault line applies stress to the rock in the fault zone
  2. This movement transfers energy into the rock and increases the elastic strain energy stores in the rock, causing the rock to deform
  3. When this deformation exceeds the frictional force holding the rocks together, a sudden slip (movement) occurs along the fault (an earthquake)
  4. This releases the accumulated stress and the rocks on either side of the fault return to their original shape, this is known as elastic rebound
  5. The energy from this sudden slip sends seismic waves through the crust and Earth to the surface
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is an active fault?

A

a fault where there is a potential source of earthquakes
- some suggestions say where there has been movement in the past 100,000 years

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Give an example of an active fault?

A

Anatolian Fault, Türkiye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

In what ways do we measure earthquakes?

A

Magnitude
Intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do we measure for magnitude?
What are we actually measuring?

A

seismometer, seismograph

actually measuring amplitude of waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is magnitude?

A
  • a number that characterises the relative size of an EQ
  • it is based on measurement of the maximum motion recorded by a seismograph (amplitude)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What issues arise when measuring earthquakes?

A

different levels of movement in different rocks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What ways can we measure magnitude?

A
  • Local or Richter (ML)
  • Moment (MW)
  • Surface wave (MS)
  • P-wave
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the Local or Richter (ML) scale?

A

The original magnitude relationship defined in 1935 by Richter and Gutenberg
- based on the maximum amplitude of S-waves recorded on a Wood-Anderson torsion seismograph
- ML values can be calculated using data from modern instruments
- L stands for Local because it only applies to EQ relatively close to the seismic station

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does moment (MW) measure magnitude?

A

Based on the seismic moment of the EQ, which is equal to the average amount of displacement on the fault multiplied by the fault area that slipped.
- it can also be estimated from seismic data if the seismometer is tuned to detect long-period body waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How can Surface Waves (MS) be used to measure magnitude?

A

A magnitude for distant earthquakes based on the amplitude of surface waves measured at a period near 20s

17
Q

How can P-waves be used to measure magnitude?

A
  • based on P-wave AMPLITUDE

Technique is being increasingly used to provide very rapid magnitude estimates so that early warnings can be sent to utility and transportation operators to shut down equipment before the larger (but slower) S-waves arrive

18
Q

What are the similarities between all the magnitude measuring systems?

A

All are logarithmic
- amplitude of ground motion increases by x10 each time
- energy increases by x32 each time

19
Q

Why do earthquakes happen at transform plate boundaries?

A

as the jagged sides catch on each other/where a transform boundary meets a divergent boundary (fault) it creates a huge build up of pressure, then as it slips it will all be released at once, causing a big EQ

  • two conflicting movement types mean more movement is going on so it is more likely for pressure and impact