Seismic hazards Flashcards
1
Q
Earthquake
A
- Shaking vibration of the Earth’s crust = movement of plate tectonics
- Can happen along any plate boundary
2
Q
When do they occur
A
- Tension is released from inside crust
- Pressure builds when the plates move
3
Q
Focus
A
- Point inside the crust where pressure is released
4
Q
Epicentre
A
- Point on the earth’s surface above the focus
5
Q
Seismic waves
A
- Earthquake energy, spread from the focus
- Strongest at epicentre and lose energy when they travel
6
Q
Distribution
A
- Occur along every plate boundary
- Long, narrow, uneven belts
- Wider clustered belts
- Dense clustering = Ring of fire
7
Q
Constructive
A
- Some earthquakes
- Depth = close to surface
8
Q
Destructive
A
- Majority of earthquakes
- Horizontal spread - widest spread along plate boundary
- Depth = shallow
9
Q
Conservative
A
- Lots of earthquakes
- Horizontal spread = narrow spread along plate boundary
- Depth = very shallow
10
Q
Intraplate
A
- Occurs in the interior of tectonic plate = relatively rare
- Don’t know causes - rising magma at hotspots?
11
Q
Interplate
A
- Occurs at the plate boundary
- More common
12
Q
How are earthquakes measured?
A
- Seismographs = Seismogram
- Difference in position between the shaking part of the seismograph and the motionless part is what is recorded.
Size = magnitude
Effect = intensity
13
Q
Richter scale
A
- Logarithmic scale
- Measures magnitudes
- Energy relese is proportional to the magnitude
14
Q
Modified mercalli scale
A
- Intensity of an event and the impact
- 12 point scale
15
Q
Seismic records
A
- Enable earthquake frequency to be observed - only date back to 1848
