earthquakes Flashcards
How does earthquake magnitude differ from intensity?
Magnitude = the amount of energy released resulting in strength of shaking aka. ground motion
Intensity = how people perceive shaking & structural impact based on location
How do Mercalli scales work?
12 intensity divisions based on the severity of shaking at a given location
How do moment magnitude scales work?
A measure of the energy released based on the seismic moment, fault rupture area, amount of movement or slip, and rigidity of rocks
Seismographs record seismic moment
How do Richter scales work?
Measures magnitude based on the amplitude of the largest seismic wave
Converted to magnitude on a logarithmic scale
How are active, potentially active, and inactive faults defined?
Active = fault has moved during the past 10,000 years
Potentially active = active between 10,000 and 1.65 million years
Inactive = has not been active for longer than 1.65 million years
What are strike-slip faults, dip-slip faults, reverse faults, and normal faults?
- Strike-slip = sides are displaced horizontally (right/left-lateral (side moving towards you))
- Dip-slip = vertical displacement that can be either normal or reversed
- Reverse = hanging-wall moving up relative to foot-wall
- Normal = hanging-wall moving down relative to foot-wall
What is the focus and epicenter of an earthquake?
Focus = point at depth where rocks rupture to produce earthquakes
Epicenter = the location on the surface above the focus
What are the types of waves produced by earthquakes and differences between them?
P-waves = body/compressional wave, fast-moving, can go through any state of matter
S-waves = shear wave, side-by-side side motion, slower than P-waves, cannot go through liquids
R-waves = surface waves, rolling motion, slower than p- or s-waves but are the most damaging as they occur on the surface
How is earthquake intensity characterized?
- How people perceive the shaking
- Hpw structures respond to it
- How far the location is from the focus/epicenter
