Tsunami Flashcards
Tsunami definition
Displacement of water due to external forces
Example of cause
Earthquake rupture to the seafloor which pushes the water upwards ( vertical and large scale)
Typical magnitude
> 6
Wave speed
900km/hr
As the wave nears land…
Decrease speed 45 km/hr
Increasing height
Velocity in deep water
~800
Wave length between the crests
~100km
deep water water height
10
Shallow water wave length
5
Shallow water wave height
10
what is the difference between wind and tsunami made waves
Wind has low speed, wavelength but more regular occurrence
Tsunami lead incidents have less reoccurrence and high speed and wavelength
What is trough
water retreat
What is crest
water rise
What is the behavior of a tsunami dependent on?
geometry and bathymetry
How many volcanic eruptions are the main trigger of a tsunami
5%
Tsunami triggers
Earthquake
Volcanic Eruption
slope failure
Meteorite Impact
What is bathymetry
study of underwater depth of ocean, lake and river floors.
Date of the Krakatau Indonesia tsunami event
1883, 2018
What was the 1883 event
VEI 6 eruption, PDCs entered
sea, >36,000 deaths
What was the 2018 event
Eruption caused Anak Krakatau’
to collapse into sea tsunami > 420
deaths
La Palma flank collapse event
Part of the island collapsed into the sea
1.1 mag collapse and 0.56 collapse
Lituya Bay, Alaska 1958 event
Mag 7.7 earthquake triggering a landslide
30.5mill m3 rocks
local surge of water in bay scoured trees
Local tsunami 20-70 m high
Lisbon
1755, 60,000 dead
Krakatoa
1883, 36,000 related deaths
Japan
1896, 30,000 dead
Alaska
1964 , 11 dead
Papua New Guinea
1998, 2500 dead
Sumatra
2004, >230,000
Tohoku
2011 , >15,000
Indonesia
2018, >280
Primary Hazards in relation to inundation of water
Loss of life via drowning and debris impact
flooding and erosion
damage to structures
Secondary hazards
polluted water supplies fires
transport disruption
disease outbreaks
Minimising tsunami hazard
deposit records
historical documentation
valuable for calculating recurrence intervals
Vulnerability modification plans
run-up maps
hazard maps and zones
land use planning ( buffer zones)
evac plans
Detection and warning systems
pacific tsunami warning system, deep ocean assessment and reporting Tsunamis
Seismomeeters, tidal gauges and tsunameters
Minimising tsunamis via…
building codes - design and construction requirements
Seawallls and barriers
Vegetation
Most expensive earthquake triggered tsunamis
2011, Tohoku tsunami
Most deadliest earthquake triggered tsunamis
2004 Indian Ocean tsunami
Tohoku tsunami date
11th March 2021
Tohoku tsunami Mag
mag 9
Tohoku tsunami epicenter
70 km
Tohoku tsunami focus
30km
true or false largest ever recorded in japan
true
Hitting the coast
10 mins
Water travelling inland
10 km
height of waves overtopping the defences
> 8.5
deaths
> 15,000
Rebulding costs
£189 bill
What was the % of those who headed tsunami warnings immediately
58%
What was the % of those attempting to evacuate but were caught in tsunami
5
What was the % of those who didn’t heed the warning ad hit by the water
49%
Indian Ocean tsunami date
26 December 2004
Indian Ocean tsunami epicenter
255km
Indian Ocean tsunami Mag
9.2
Indian Ocean tsunami focus
30 km
How many countries affected by the Indian Ocean tsunami
14
Cost of Indian Ocean tsunami
£15 bill
number of deaths during the Indian Ocean tsunami
> 230,000
Movement
Indian and Australian plates being subducted NE beneath Burma microplate at 6cm/yr
Movement of the Burma microplate and what rupture
~20m along a 1500 km rupture
What type of event is this
Mega - thrust event
How the tsunami occured
Displacement of seafloor disturbed water
What were the rescue and relief measures
Ports destroyed
14 countries requesting aid
Money collection required
Environmental long term impacts
Destroyed ecosystems ( mangroves ,coral reefs coastal wetlands and forests
Arable land contamination by salt
Contamination of freshwater supplies
What happened ( economically ) during 2004-2007
UNEP: US $9.3 mill for environmental recovery and disaster reduction
Economic long term impacts
Local economies destroyed
Fishing and tourism hardest hit
Damage to infrastructure
