Unit 2 - Earthquakes Flashcards
(19 cards)
About how many total earthquakes of any size occur globally each year.
1.3 million, but most are very small.
The largest earthquake to occur on Earth over the past 100 years
Occurred in Chile in 1960, magnitude of 9.5, lasted 11 minutes
Where most earthquakes occur
plate boundaries
earthquake
A sudden break in the crust after a long period of stress buildup due to motions of tectonic plates.
The concept of elastic rebound
When the crust bends like rubber (storing energy), then unbends (releasing energy), like it’s a piece of rubber
The concept of stick-slip behavior
When faults remain stuck while energy builds, then suddenly slip when energy is released.
asperities
the rough edges that grind each other down
why does slipstick occur
Stick-slip occurs because friction and rough spots (protrusions) along the fault (called asperities) prevent the fault from sliding until they can be overcome.
How we observe the buildup of stress on a fault.
Can be observed using very precise GPS
Where thrust faults occur.
Occurs in compressional settings like subduction zones
Where normal faults occur.
Occurs in extensional settings like mid ocean ridges
Where transform (strike-slip) faults occur
Occurs in settings where plates slide laterally past each other like transform boundaries
What an earthquake hypocenter is.
Location at depth where the earthquake started.
Characteristics of P waves.
(Stands for primary or pressure waves)
push-pull motion (compresses then expands like a sound wave)
Travels through solids, liquids, and gasses
Fastest seismic waves (first to arrive), but cause the least shaking
Characteristics of S waves.
(S for secondary or shear)
Side to side motion (shear)
Travel only through solids
S-waves’ energy can convert into P-waves so it may travel through the liquid outer core
P-waves can also convert back to S-waves in the solid inner core
Slower than P-waves (second to arrive)
Characteristics of surface waves
Love Waves
Side to side motion
Travel only along the surface of a solid
Rayleigh Waves
Up-down motion like an ocean wave
Travel only along the surface of a solid
Surface waves are the last to arrive, but cause the most deformation
How we know that the outer core of the Earth is liquid
The refraction of p-waves as they crossed over to the inner core shows us that the inner core is solid
discover outer core was liquid from the s-wave shadow zone
How much the amount of shaking varies between different magnitude earthquakes.
Each unit increase in earthquake magnitude corresponding to a factor of 10 increase in shaking
ex. M5 is 10 times amount of shaking from M4
The theoretical maximum magnitude earthquake that can occur.
M9.5 because that’s the largest fault that could slide.
