Why do earthquakes occur? correct answers - release of energy in response to a build up of stress along a fracture
- energy released in sudden bursts due to stick-slip behavior
Why do we see stick slip behavior? correct answers faults are not smooth so the jagged edge causes friction
What ar...
EESC 101 Exam 2 || A+ Graded Already.
Why do earthquakes occur? correct answers - release of energy in response to a build up of stress
along a fracture
- energy released in sudden bursts due to stick-slip behavior
Why do we see stick slip behavior? correct answers faults are not smooth so the jagged edge
causes friction
What are the four different types of faults? correct answers - normal faults (with gravity)
- transform faults (sideways motion)
- reverse faults (against gravity, high angle)
- thrust faults (against gravity, low angle)
At what depths do earthquakes occur and why? correct answers - anywhere from the surface to
660km deep
- at 660km, you reach the mantle; rock becomes liquid and won't strike-slip
At what depths are different earthquakes labeled? correct answers - shallow, <20 km
- intermediate, 20-300km
- deep, 300-660km
Focus correct answers the point at which an earthquake originates within the crust (deeper = less
damage, shallower = more damage)
Epicenter correct answers the point on the surface directly above the focus
Displacement (offset) correct answers the amount of movement across a fault
- most only move a few centimeters, but big ones can be 7-12 meters
- enormous amounts of energy released
Can there be movement at a fault but no earthquake occur? correct answers yeah!
- <15km, Fault Creeps, really small, slow movements that doesn't result in an earthquake (still a
fracture/sone of weakness)
- >15km, its too hot so it reacts elastically (think cold vs hard plastic bending)
Where do earthquakes occur? correct answers - mostly at plate boundaries
- transform/divergent boundaries (shallow only, continental rift areas more dangerous than
MOR)
- convergent boundaries (all depths, often near coast lines)
Inactive correct answers old faults that haven't caused earthquakes in millions of years (still areas
of weakness!)
Intraplate Earthquakes correct answers earthquakes far from any plate boundary, likely caused
by the reactivation of ancient faults
, What causes earthquakes? correct answers 1. sudden formation of a new fault
2. sudden slip on an existing fault
(top two are 90% of earthquakes)
3. mineral phase change
4. movement of magma in a volcano
5. volcanic eruption
6. meteoric impact
7. nuclear bomb test
8. pumping fluids into/out of the ground
1. Sudden formation of a new fault correct answers constant application of pressure in opposing
direction creates new permanent zones of weakness
2. Sudden slip on an existing fault correct answers most common; old faults are zones of
weakness so they tend to break and move to release energy
4. Movement of magma in Volcanoes correct answers rising magma wedges into pre-existing
fractures, can signal upcoming eruptions
8. Injection of fluids correct answers - creates new weaknesses, fluids can spill, gets into the
groundwater
- can lubricate faults so they slip more easily
- pumping water in and out can create small fractures/wedge in the current ones
Seismology correct answers the study of earthquakes
Seismic Waves correct answers tremors we feel, responding to the energy released
Seismograph correct answers used to detect and locate earthquakes
Seismogram correct answers the data recorded from a seismograph, depicts arrival times of
waves which helps find the epicenter
What are the four different types of waves? correct answers Body waves (travel through the
earth) - primary and secondary
Surface waves (travel along the surface) - love and rayleigh
Primary Waves - P-Waves correct answers - compress and expand parallel to the wave-travel
direction
- fastest seismic wave
- travel through solids, liquids, and gasses
- little damage at surface
Secondary Waves - S-Waves correct answers - travel back and forth perpendicular to the wave-
travel direction
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