Earthquakes Flashcards
Earthquakes are a result of?
Plate techtonic motions
What causes earthquakes? (4 ways)
Slip along faults(most common)
Change in mineral structure
Movement of magma in a volcano
Volcano Eruption
the place where fault slip occurs is called?
A hypocenter
How can 3 ways faults react to their environment?
Faults can get reactivated
Faults store and then release energy
Faults move in a stick slip behavior
Where do hypocenters occur and how do earthquake waves move?
fault surface, outwards
What is the land surface above a hypocenter?
Epicenter
What are faults?
like planar breaks in blocks of crust
Do most faults have a slope?
Yes (rarely they can be vertical)
On a sloping fault, crustal blocks are classified as?
Footwall(block below the fault)
Hanging wall (block above the fault)
What is a thrust fault, and where is it found?
A special kind of reverse fault and its found in compressional mountain belts
Differentiate between Active and Inactive faults
Active=ongoing stress produces motion
Inactive=motion occurred in the geologic past
What does a fault trace show?
fault intersecting the ground
Define stick-slip behavior
Stick-friction prevents motion
Slip-friction is briefly overwhelmed by motion
How do seismic waves travel?
compressing and expanding material
What seismic waves are the fastest?
P waves
Where do surface waves travel?
Along the Earth’s exterior
What waves are the most destructive?
surface
What are L-waves and how do they move?
S-waves that intersect the land surface, move the ground back and forth like a writing snake
What are seismographs?
instruments that record ground motion
How do seismographs record these motions?
Vertical- records up and down movement
Horizontal-records back and forth movement
What order do earthquakes arrive at a station in?
P-waves first, S-waves second, surface waves last
How is an earthquake’s size measured?
severity of damage (intensity)
ground motion (magnitude)
What is liqueification?
waves occupy H2O filled sediments, causes quicksand to form, reduces friction, unstable land cracks
