Lesson 4 Flashcards
What is the Wadati-Benioff zone?
When a decending oceanic plate is in contact with a continental plate as it is subjected creating a lot of stress and when released causes an earthquake
Key features of primary waves?
moves fast
moves through rock & liquid
compresses in direction of travel
Short wave length
Key features of secondary waves?
Slower than primary wave
Moves through solid rock
up & down movements
Long wave lengths
Rayleigh waves key features?
Travels in rolling motions
Responsible for most shaking felt by people
Only travels through surface of crust
Love wave key features?
Only travels through surface of crust
Fastest surface wave
Moves horizontal
What is the focus of an earthquake where all strain is released called?
A shockwave
What do shockwaves do?
Sends seismic waves in all directions strongest at the point on the earths surface.
What happens first in shockwaves?
P waves arrive first with a short wave length and travel quickly through the crust
What happens second in shockwaves?
S waves arrive seconds later which have a longer wave length with a velocity of 4 km/s causing more destruction
What is the shockwaves case study called?
Tohuku in Japan 2011
What happened in Tohuku?
S waves reached Tokyo 90 seconds after the release of stress. When all shockwaves where combined over a period of 30 seconds buildings where damaged
What does a tsunami consist of?
Sequences of waves with a deep trough because the water is drawn upwards into each wave
Why are tsunamis hardly noticeable in deep water?
Due to a long wave length
Why are tsunamis noticeable in shallow water?
friction slows them down shortening the wave length and building height
What are tsunamis created by?
water column displacement by underwater plate movement
