Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

EOS410PltTec > Earthquakes > Flashcards

Earthquakes Flashcards

1
Q

Plate Boundaries: Trench

A
  • Ocean-Ocean

- Ocean-Continent

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

Plate Boundaries: Collision

A
  • Continent-Continent

- Ocean-Ocean only when thick collides with thin

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

Plate Boundaries: Transform

A
  • Continent-Continent
  • Ocean-Ocean
  • Ocean-Continent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Plate Boundaries: Ridge

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

Plate Boundaries: Rift

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

Shallow focus:

A

< 70km depth

- all plate boundaries

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Intermediate focus:

A

70-300km

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

Deep focus:

A

> 300km

- Only convergent

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

Wider bands of seismicity are typically what type of boundary?

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

Seismicity deepening from trench

A

Wadati-Benioff zone

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

What is a possible explanation for deep EQ’s on a collision margin (Himalayas)

A
  • Remnant ocean slab under Himalayas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why does the Cascade zone show only shallow EQ’s unlike other subduction zones (deep)?

A
  • Locked for a very long time frame, no data collected before 1975
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why do extensional EQ’s occur in a compression zone (subduction)?

A
  • Not enough material on surface to cover the bending/bulging area of subducting slab
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is sense of motion on fracture zones that connect MOR’s?

A

Transform

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

Elastic Rebound Theory

A
  • Following 1906 San Fran EQ fault offset
  • ‘Stretch over a time (short or long) until rupture and slip
  • Dip doesn’t necessarily tell you type of slip
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Types of Faults

A
  • Strike-slip
  • Normal
  • Thrust (Reverse)
  • Oblique
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Hypocentre (focus) vs. Epicenter

A
  • Focus - Fault surface location (at depth)

- Epicenter = Earth surface above focus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which is the first seismic wave to arrive? Second? Last?

A
  • P-wave
  • S-wave
  • Surface (Love and Rayleigh)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does the s-wave minus p-wave arrival time indicate?

A
  • Distance to focus
  • Further apart = further from focus
  • Only for local/regional, outside this the linear model (dist/time) falls apart
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Concepts of seismicity

A
  • Seismicity defines plate boundaries

- Seismic wave arrivals at different stations provide info on location (S minus P arrival times)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

P-wave first motions

A
  • Up/down = Compression/Dilation
  • Fault plane
  • Mechanism
  • Slip direction
22
Q

Seismic waves: Body waves

A

P-waves, S-waves

23
Q

P-waves

A
  • Primary (fastest), push-pull
  • Elastic deformation by compression/dilation in propagation direction
  • Travel through solids, liquids, gasses
24
Q

S-waves

A
  • Secondary, shear
  • Elastic deformation by shearing perpendicular to propagation direction
  • Only travels through solids
25
Q

Leading Push

A

Compress then extend

  • Compression
  • Upward first motion
  • Towards receiver
26
Q

Leading Pull

A

Extend then compress

  • Dilation
  • Downward first motion
  • Away from receiver
27
Q

Ground motion at an observed receiver

A

Direction related to fault motion

28
Q

What are the 2 nodal planes?

A
  • Fault plane

- Auxiliary plane 90 degrees to fault plane

29
Q

For a vertical fault strike-slip example, what are the 1st motions at stations along nodal planes?

A

Zero, neither up or down

30
Q

What are the possible motions on the nodal planes for vertical fault strike-slip? Is this the same for Normal and Thrust slip?

A
  • Either dextral motion on one plane
  • or Sinistral on the other plane
  • Can’t tell which is FP or AP
  • Normal and Thrust remain the same no matter which plane is the FP/AP, just orientation changes
31
Q

How do you tell which nodal plane is the fault plane?

A
  • Can’t tell without geological or geophysical evidence
  • Surface trace, bathymetry
  • Maybe GPS data
32
Q

Fault plane solutions

A
  • Usually in map view

- Lower hemisphere

33
Q

Pressure axis P

A
  • Max compressive stress direction
  • In tensional quadrant at 45 degrees to both nodal planes
  • Sigma 1
34
Q

Tension axis P

A
  • Minimum compressive stress direction
  • In compressional quadrant at 45 degrees to nodal planes
  • Sigma 3
35
Q

P and T axis in vertical strike-slip fault

A

Both horizontal

36
Q

P and T axis in thrust fault dipping 45 degrees

A
  • P-axis is horizontal

- T-axis is vertical

37
Q

P and T axis in normal fault dipping 45 degrees

A
  • P-axis is vertical

- T-axis is horizontal

38
Q

Focal Sphere

A

Unit sphere centered on EQ focus

39
Q

1st motions recorded at stations provide what info?

A
  • Pattern of P-waves leaving the lower half of focal sphere
  • Only lower sphere b/c they bend upwards towards surface by refraction since velocities increase downwards while upper sphere bends downwards into Earth
40
Q

Nisqually EQ

A
  • 2001
  • Mw 6.8
  • 58km depth
41
Q

Stereonets

A
  • Projections of lower hemisphere onto horizontal plane
  • Intersection of a line w/ hemisphere = point
  • Intersection of a plane w/ hemisphere = Great circle
  • Line normal to a great circle is a point 90 degrees away from centre of circle = pole (line w/ plunge 90 degrees from dip of plane
  • Pole of fault plane is a point on stereonet in the auxiliary plane and vice versa
42
Q

How to find angle btwn 2 lines on stereonet

A
  • Given trend and plunge of 2 lines
  • Mark both ends of strike on circle circumference
  • Rotate overlay to line strike up w/ equator, count in plunge and mark point, repeat for 2nd point
  • Rotate overlay so points lie on common GC, count degrees along circle
  • Rotate N back to top, read off strike and dip of plane on which both lines lie
43
Q

Given a pole, find strike and dip of a plane on a stereonet

A
  • Rotate pole until it lies on equator
  • Count off the dip from the centre of the net
  • The GC lies 90 degrees away
  • Mark strike of the plane at the ends of the N-S meridian
  • Rotate overlay to N and measure the strike
44
Q

What happens if motion occurs along auxiliary plane for Normal or Thrust EQ’s?

A

The same compressional/dilational pattern will occur

45
Q

Motion

A
  • Direction of motion/slip on fault plane
  • Vector made up of strike component and dip component
  • Pole of auxiliary plane
46
Q

Horizontal

A
  • Direction of slip projected to the horizontal
47
Q

Plunge

A
  • Angle between Horizontal and Motion

- Does not lie on fault plane

48
Q

Rake/pitch

A
  • Angle btwn Motion and Strike

- In the fault plane

49
Q

Why is M the pole of the aux plane?

A
  • No velocity component in Aux plane
  • Only 2 nodal planes, one is fault, parallel to motion
  • Therefore pole to aux must be M
50
Q

Great Success of modern plate tectonics era

A
  1. Motions of continents predicted from paleomagnetic data and confirmed w/ geophysics and geochronology
  2. Explanation of seafloor magnetics, mechanism is seafloor spreading
  3. Magnetic stripe prediction of ocean crust ages confirmed by sedimentology/paleontology
  4. Motions at transform faults confirmed w/ seismology
51
Q

Transcurrent vs. Transform

A
  • Markers offset
    vs.
  • Fault btwn ridge segments

EOS410PltTec (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions