1.9 - Tsunamis, Tohoku Flashcards
1
Q
How are tsunamis initiated?
A
- earthquake causes seabed to thrust upward
- displaces water column above it
- displaced waves becomes a tsunami wave
- can also be caused by landslides (submarine ones as well)
2
Q
What are the properties of a tsunami wave in open water?
A
- has a long wavelength
- travels at 500mph
- amplitude is low
3
Q
What are the properties of a tsunami wave in shallow water?
A
- friction against the sea bed increases
- Wave speed decreases ≈ 40kph
- wavelength of wave decreases
- amplitude increases
- results in higher waves
- naturally have large amount of energy when they hit the shore
4
Q
What is the hypocentre?
A
- another word for focus
- where the EQ starts
- found in the Benioff Zone
5
Q
What factors is a tsunami’s effect subject to?
A
- distance from source
- bathymetry of coastal water
- shape of coastline
- how much plates have displaced
6
Q
What does bathymetry mean?
A
- depth of an area of sea
- The topography of the sea bed
7
Q
How does the shape of the coastline effect the affects of a tsunami?
A
- affects the height of waves
- if the coastline is shaped like an estuary, the waves are funnelled up it
- this means that the waves are higher
8
Q
What happens off the coast of Japan?
A
- The Pacific plate subducts below the Okhotsk micro plate
- an ocean trench forms
