Chapter 9 - Premidterm Flashcards
Degree of destruction of earthquake is dreependent on:
Magnitude of quake
bedrock
type of structure
How does bedrock correlate with earthquake? How can u use bedrock to your advantage
If you build structures on strong bedrock, magnitude of earthquake wave is smaller
-softer material, clay, water, large magnitude. CAREFUL
Other factors making earthquakes dangerous
Fires due to rupture of gas lines
land slides
What is hypocenter or focus of earthquake
exact point where it is caused
What is epicentre of earthquake
Point on surface right above hypocenter
Where do earthquakes occur
Most earthquakes occur in seismic belt corresponding to plate boundaries converge, diverge, transform
Can you build a house with 100% earthquake safety?
No. You can make the percentage very high, but earthquakes can occur anywhere
What is elastic rebound theory. What does it say
Explains causes of earthquakes
-stress builds up between 2 different piece of lands, then it ruptures and moves apart, stress is released in shockwaves
What are 4 types of shockwaves
P waves
Secondary wave
Rayleigh wave (r) wave
Loe wave (L) wave
Describe P wave
Compressional wave
- travels same direction as deformation
- MOST DESTRUCTIVE, fastest waves
- longitudinal waves
Describe secondary waves
Shear waves
- slower than primary wave, less destructive
- moves at a right angle with direction of wave / with direction of P wave
- moves up and down
- shear objects, since liquids and gas aren’t solid, there is no shear stress, and there is no Secondary waves
Rayleigh wave, describe!
Slower, behaves like water waves
-moves forward, while particles move in an elliptical path within a vertical plane
Love wave, describe
Like S waves, but particles move back and forth in horizontal plane perpendicular to direction of wave
CAN S WAVES TRAVEL THROUGH SOLIDS GASES, WHY
NO CUZ OF SHEAR STRESS, NO SHEAR STRESS IN LIQUIDS GASES
CAN P WAVES TRAVEL THRU SOLIDS GASES?
YES
What are body waves
P and S waves
What are surface waves
L and R (love and Rayleigh waves)
Intensity vs magnitude of earthquake?
intensity is subjective, depends on how much damage done
magnitude is amount of energy released
What scale is intensity of earthquake?
Modified mercalli intensity scale
-dependent on distance, population, types of buildings, like how much destruction done, intensity is subjective
What scale is magnitude of earthquake?
Richter scale
- measured by largest amplitude of seismic wave
- on a log scale so difference between 5 and mag is 10
How do we determine where epicentre of earthquake is?
Distance between arrival of P and S waves.
-we know velocities of both waves, so we can use that to determine
How many seismic graphs do we need to determine where epicentre is?
3 seismic graphs
For an area that just got an earthquake, whats the likelihood of another earthquake in same area?
Stresses accumulate in bedrock
- when earthquake happens, that rock breaks, releases all the stress
- if it recently had an earthquake, not likely it will happen
How did we figure out the outer core to mantle boundary? How do we figure out outer mantle is liquid?
S waves cannot penetrate liquids
- when they hit liquid outer core, they get blocked off
- SHADOW ZONE
