All shook up Earthquakes can be frightening events Click on left image for short video Earthquakes Usually happen near faults What are faults Many faults are near plate boundaries but they can be anywhere and everywhere ID: 497741
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Slide1
SEISMOLOGY
(All shook up.)Slide2
Earthquakes can be frightening events.
(Click on left image for short video.)Slide3
Earthquakes
Usually happen near
faults.
(What are faults?)Many faults are near plate boundaries, but they can be anywhere and everywhere.
Over one million earthquakes per year (one every thirty seconds).
Most are too small to be felt.
But, there are several hundred powerful, damaging ones per year.Slide4
Faults –
breaks or cracks in the crust where movement can occur.Slide5
California – it’s their fault(s).Slide6
Epicenter vs
Focus
(Can you see the difference?)Slide7
Seismic Waves
P-Waves
S-Waves
L-Waves
(aka Surface Waves)Slide8
SeismographsSlide9
The Richter Scale:
Measures the magnitude (amount of energy released).
0-10 scale.
Devised by Charles Richter in 1935.Slide10
The Richter Scale is logarithmic
.
(What does that mean?)
It goes up exponentially.Going up one whole number means a ten times more powerful quake!
So going up two whole numbers means a 100 times more powerful quake!!Slide11
Most powerful earthquakes ever recorded.Slide12
The Mercalli
Intensity Scale
(measures DAMAGE caused)Slide13
Megathrust Earthquakes
By far the most destructive of allSlide14
Megathrust
quakes:
Happen at
subduction zones.
Since 1900, all six 9.0 or greater quakes.
Can produce tremendous tsunamis (ex. Southeast Asia in 2004
and Japan in 2011)
The Cascadia
Subduction
Zone is a very likely spot for a
megathrust
and a tsunami.
Click on image for short video (0:28)Slide15
The Cascadia Subduction
Zone is a likely site for a
megathrust quake and a tsunami. It’s happened there before.
(Click for video 2:45)Slide16
Tsunamis are terrifying.
(Click on image for video 2:44) Slide17
But not to worry!
Earthquakes or tsunamis can’t happen here.
Right?Slide18
Think again.
(A map of U.S. earthquake risk below.)Slide19
But
we (on the East Coast) are
nowhere near a subduction
zone, so the threat of a tsunami from a megathrust quake is impossible.But is there another way to trigger a tsunami?Slide20
Meet Cumbre
Vieja, a volcano in the Canary Islands, just off the coast of Africa. Slide21
Some scientists predict that a landslide form a
Cumbre
Vieja
eruption could produce not just a tsunami but an enormous MEGATSUNAMI. Good grief.(Click on image for a video 7:35)