Week 3 Flashcards
1
Q
Faults and Seismicity
A
- Faults are breaks in the rock where it has been broken apart by applied stress
- There are different varieties of faults, based on how they have broken due to stress.
- Main physical feature that earthquakes leave behind.
2
Q
2 Main types of faults
A
- Normal faults (When the overriding block moves down)
- Reverse Faults (When the overriding block moves up)
- Strike Slip Faults (Transform) (When 2 blocks slide past one another instead of vertically)
3
Q
Body Waves
A
Through Interior
P – Waves (Primary Waves)
S – Waves (Secondary Waves)
4
Q
P – Waves (Primary Waves)
A
- Travel faster then S – Waves
- Compressional motion
5
Q
S – Waves (Secondary Waves)
A
- Torsional motion
- Slower, but often cause more violent shaking.
6
Q
Surface Waves
A
Through the surface of the Earth
Love Waves
Rayleigh Waves
7
Q
Love Waves
A
- Transverse surface motion
- Waves move along zigzag along the surface.
- Very destructive
8
Q
Rayleigh Waves
A
- Rolling surface motion
- Waves cause the surface to “roll” like waves in water.
- Very destructive
9
Q
Three plate boundaries associated with Plate Tectonics
A
Divergent Boundaries
Convergent Boundaries
Transform Boundaries
10
Q
Divergent Boundaries
A
- New crust forming at centre
- Extensional stress, with each side pulling apart
- Earthquakes often occur close to the surface and are low magnitude
- Low explosivity volcanism, instead lava ‘flows’ out non-violently
11
Q
Convergent Boundaries
A
- Oceanic (heavy) crust sinks below Continental (light) crust
- Friction causes earthquakes from surface to more than 300km deep
- Compressional stress, often high magnitude and associated volcanoes
12
Q
Transform Boundaries
A
- Crust moves in opposite directions, causing shearing friction
- Best example is San Andreas Fault in California, causing nearly all earthquakes
- We will learn more about these boundaries in later chapters when we look at catastrophic earthquakes in California
