CH 6 - Tsunamis

terms/case studies/properties

tsunami

waves generated by large changes in the ocean or lake floor

causes of tsunamis (4)

• seafloor shifting

• submarine / subaerial landslide

• blast from an explosive volcanic eruption

• meteorite impact

tsunami wave properties

• wavelength? speed? amplitudes+why?

• long wavelength

• travel fast

• small amplitude in deep water

• higher amplitude in shallow water - faster water catches up to slower water @ leading edge of wave

wind driven waves

• frequency? water levels?

• rise + fall quickly

• water lvl may drop before first wave

Case study: indian ocean tsunami

• year

• magnitude

• main takeaways

• 2004

• Mw = 9.3 - trench near Sumatra

• 15m high wave - 230k dead

• warning systems werent in place yet

Case Study: EQ- Landslide-Tsunami, Lituya bay, Alaska

• year

• magnitude

• cause - effects

• 1958

• Mw=7.8 - 30mil cubic feet fell into bay

• water was 524m high-continued toward coast at 100 ft high

Case study: tsunami from submarine slide, Storegga, Norway

• year

• cause

• effects

• 8000 years ago

• place of continental shelf slid way

• nearby stone age villages were destroyed

Continental shelf

flat, shallow platform near the coast

Case study: volcanic island mega-slide, cape verde

• time

• cause + effects

• main takeaways

• 73k years ago

• fogo island flank/side collapsed - 250m high wave front

• tsunami hit santiago + moved giant rocks

• many volcanic islands like this (Hawaii)

Tsunami predictions (2)

seismic data trigger tsunami watches - cant confirm tsunami occurring

DART bouys

DART buoys

tsunami pressure pulse @ ocean bottom - trigger buoy alert - gives ppl time to evacuate

Tsunami disaster mitigation (5)

• warning systems

• public education

• tsunami inundation maps - community planning

• evacuation destinations

• seawalls

tsunami inundation maps

• prevent building in danger zones

• abandoned buildings in danger zones

• zoning

Zoning

putting nature parks in danger zones