lecture 15

Question 1

what are the 3 stages of tsunami wave

Answer 1

1. generation: seafloor motion pushes up column of water
2. propagation: as seabed shallows, speed slows and height grows (500-800km/hr)
3. indundation: energy dissapates as water spreads over large area

Question 2

sources of tsunami generation

Answer 2

anything that dispalces the ocean water column

ex. volcanoes, landslides, meteorite impacts, earthquakes

Question 3

what does geographical reach depend on

Answer 3

volume of water displaces
ex. megathrust earthquakes uplift over 1000s of kms which generates ocean wide tsunamis
landslides are <1km so can produce local or regional tsunamis

Question 4

water waves

Answer 4

pulses of energy that move through water mass causing water molecules to rotate in place
- flattens orbits as enter shallow water which decreases wavelengthand concentrates wave energy, heights increase (SHOALING)

Question 5

wind waves

Answer 5

created by friction at wind/ocean surface

• size, frequency and period determined by velocity, duration and consistency of wind with water
• water runup/retreat is confined to the beach

Question 6

tsunami run up

Answer 6

arrive as the leading edge of elevated mass of water

• run up and over beach which floods inlands
• might not be tall but have large momentum and a mass of water and debris

Question 7

tsunami propagation

Answer 7

long wavelength means waves can bend around islands and hit all shorelines by refracting and hit all sides of an island

Question 8

tsunami inudation

Answer 8

when entering shallow water the wave slows down and amplitude increases, run up heights depend on nearshore bathymetry and shape of coastline
- waterdrawback occurs if trough arrives first

Question 9

seiche

Answer 9

standing wave in enclosed or partially enclosed body of water that sloshs back and forth across bays, lakes or swimming pools
- common in great lakes

Question 10

lake superior 2001

Answer 10

seiche that reached dangerous heights

Question 11

lake michigan

Answer 11

experienced deadly seiches in 1929 that killed 10, 1938 killed 5 and 1954 killed 8
- april 2018 ahd a. small seiche

Question 12

lake erie

Answer 12

prone to seiches due to shallow water depth and alignment with prevailing south-westerly winds
- buffalo at east end, toledo at west and cleveland in middle

Question 13

japan earthquake–>

Answer 13

small seiche in norweigan fjord caused by 9.0 japan earthquake 80000km away