Engineering Geology and Geohazards Lecture 15: Tsunamis

Question 1

How long is a tsunami wave train and what is the amplitude

Answer 1

Wave train formed from waves of wavelength up to
200km, depending on the source. Conserves energy.

Amplitude about 1m in mid ocean. Period 5-60 minutes.

Question 2

Describe the speed of tsunamis

Answer 2

Speed >700km/h in deep ocean, (4km deep) around

100km/h on continental shelves (100m deep).

Question 3

How do tsunamis behave in different depths of water

Answer 3

As slow in shallower water wavelength and wave period reduce, but energy is conserved so amplitude increases.

Trans-oceanic, whereas earthquake damage limited to within few hundred kilometres of epicentre.

Question 4

Describe the creation of tsunamis at a subduction zone

Answer 4

Subducting plate subducts beneath other plate (could be continental or oceanic). Causing other plate to bulge up/uplift. Causing water displacement and thus a tsunami