Tectonics 2 Flashcards
Diverge = decrease overlying pressure, converge = high pressure, all boundaries = friction, gases build up = pressure
How does Cross-Bracing help infrastructure be more earthquake-resistant?
- use two steel beams, reinforce walls
Define earthquake
Shaking of earth’s ground
sudden release energy (litosphere)
only involves fully solid litosphere along fault lines
Where do earthquakes generally occur at?
Along plate boundaries which have a system of faults
All plate boundaries have faults.
How does earthquakes form? (4 points)
- Rock masses, either side of fault pushed by [tectonic force]
- Friction causes plates get locked, stress builds up
- When stress exceeds strength of [rock/ fault], rocks [snap/suddenly move to] another position
- causes seismic waves release, result in ground shaking
https://docs.google.com/document/d/12rAwkWXiw5RGFDGpRY3RhY_ab2Cs2ZpI7u36Bog2OvM/edit?tab=t.0
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What are faults?
A system of deep fractures
What is a focus?
the place inside Earth’s crust where earthquake originates
where is the origin of an earthquake?
focus
what is the epicenter?
the point on earth’s surface directly above focus
where is shaking most strongly felt?
near the epicenter
how are earthquakes measured?
seisometers
how do the equipment to measure earthquake work?
sensitive instruments detect ground vibration, determine magnitude
Increasing what will incrase the magnitude of earthquake?
Seismic energy
released
Which scales do scientists use to rate magnitude of earthquake?
- ML (richter scale)
- Mw (Moment magnitude Scale)
How does Richter Scale place earthquakes on the scale?
- max wave height recorded (seismometer)
- based: maximum seismic intensity
Richter Scale’s characteristics
- Numbered from 1-10
- Logarithmic
Logarithmic scale seismic energy scaling
32x more energy
LINK
- Mw Scale: Moment Magnitude Scale
- ML Scale: Richter Scale
What are the limitations of Richter Scale?
underestimates longer earthquakes release more overall energy
e.g.; rate earthquake w/ 1 single drastic spike vs earthquake w/ many large waves as higher
Is the richter scale commonly used?
No
- small, local earthquakes only
How does the Moment Magnitude Scale rate earthquakes?
- total energy released during earthquake
- estimates total energy released
Which scale is more accurate? Richter or Moment Magnitude?
Moment Magnitude (Mw) generally more accurate
Characteristics of Mw Scale
- Logarithmic
Increase in 1 = 10x more powerful But 32x more seismic energy released
Example of earthquake adjust Richter -> Mw
1964 Prince William Sound Earthquake
- Readjust Richter 8.6 -> Mw 9.2 (more accurate)
What is magnitude?
Measuring amount of seismic energy
How are volcanoes created?
When lava erupts onto Earth’s surface cools, forming cone-shaped mountain
(By God, btw!)