Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Natural Hazards > Tsunami > Flashcards

Tsunami Flashcards

1
Q

What are tsunamis

A

A series of large waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are tsunamis generates by

A

Submarine earthquakes
Volcanic eruptions under or into the sea.
Landslides into or under the sea.
Comet or meteor rite impacts into the sea.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a comet

A

Icy body from outer regions of solar system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a meteorite

A

From asteroid belt near mars and Jupiter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do tsunamis need

A

Vertical displacement of water column, over large area (100-1000km^2). Gravity helps it adjust to the displacement causing the series of waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the equation for tsunamis velocity

A

Water velocity (v) controller by earths gravity (g 9.8m/m^2) and the depth of the sea (H)

V= square root of gH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the equation for tsunami amplitude related to the velocity

A

A^2v= constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do tsunamis form

A

As wave travels to the shore, depth decreases causing velocity to decrease which in turn caueee amplitude to increase. Wave slows down but get bigger.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does the tsunami wave change as it gets closer to coast

A

In middle of ocean the depth of the sea is 5000m, velocity is 224m/s and amplitude is 2m. Unrecognisable.
10km from coast the depth is 100m, velocity is 32m/s and amplitude is 5.3m.
100m from coast the depth is 1m, beockity is 3.3m/s and amplitude is 16.5m.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the tsunami characteristics offshore

A

Velocity - FAST. 900km/h
Amplitude - SMALL. Less than 2m.
wavelength - LONG. Hundreds of km.
Hazard level - LOW. Hardly noticeable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Tsunami characteristics onshore

A

Vecolity = SLOW. Few tens of km/h.
Amplitude INCREASED. Several tens of m.
Wave length DECREASES to tens of km. wave crests closer.
Hazard level INCREASED.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is a tide gauge useful in measuring tsunamis

A

Usually measure predictable undulating increase and decrease of sea level due to rises. 12 and half hours is the cycle of tides. Before tsunamis the red line follows prediction closely then there’s a huge variation. Blue-red to get tsunami irrespective of tide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What isrun up

A

Height above mean sea level that the wave reached as it rushes onsure. Usually greater than incoming wave amplitude.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is inundation

A

Horizontal distance reached, measured inland from the mean shoreline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How can run up and inundation vary considerably along a shoreline

A

Depends upon local bathymetry and topography

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Example of run up shown by scored vegetation

A

2004 tsunami at Banda Aceh , Sumatra

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Where do tsunamis occur

A

Subjection zones with large earthquakes and volcanic eruptions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Where has the highest tsunami hazard level

A

The Pacific Ocean due to the ring of fire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the percentage of tsunamis that happen in the Pacific

A

59%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the percentage of tsunamis in the Mediterranean Sea

A

25%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where else contains relatively short subduction zones

A

Indian and Atlantic oceans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the hazards of a tsunami

A

waves can knock down trees, buildings, bridges etc.
People killed by drowning or hit by debris.
Afrtermath brings water borne diseases - malaria from stagnant breeding mosquitos and sewage and decomposing bodies

23
Q

What are the ways of reducing vulnerability of tsunamis

A

Assess hazard level.
Land use planning and defence.
Education, training and emergency planning.
Tsunami warning systems.

24
Q

How to assess hazard level

A

Map deposits and erosion from previous tsunamis.
Identify source zones.
Estimate recurrence intervals -> probabilistic forecasting.
Tsunami modelling.
Hazard mapping.

25
How can you see erosion from previous tsunamis
Sometimes big boulders that have been deposited and you can’t tell how else they got there
26
How does identity source zone help
Look at past earthquakes, slope stability of underwater volcanoes and can get a rough idea of areas more vulnerable. Difficult bc big tsunamis from far away that was small when it gets to you or big ones that started close by
27
How do you get estimated recurrence intervals
Records and geological records . Look at past and extrapolate to the future for a rough idea of how frequent tsunamis are
28
How does tsunamis modelling help
Computer models that represent their behaviour - energy, grow in height, interactions with features on sea floor like islands can make them retract or bounce off coastlines they’ve hit. Give an idea of coastline with big run up and inundation
29
What does hazard mapping do
Shows evacuation routes, population, areas that need to be protected
30
What is land use planning and defences like
Use areas closest to sea for recreation only. Tsunami control forests absorb wave energy. Trees can absorb tsunami energy to try and reduce tsunamis
31
mangroves and coral reefs are effective natural defences but what’s wrong
They are often degraded or destroyed by human activities such as aquaculture, tourism, pollution
32
Why are mangroves important
Dense network of tree roots partially in and partially out of water. Important ecosystem for fish breeding in the roots. For birds and other animalsX
33
How much of the mangroves have been lost in last century
50%
34
When was there an increase in recognition of mangroves
2004
35
What do engineering solutions include
Breakwaters and sea walls but these are expensive and ugly and not always high enough
36
Example of place with high tsunami barrier
10m in Taro Japan but in March 2011 the tsunami was more than 10n high flooding taro and many other areas. Water is trapped then
37
When can tsunamis be detected
Several hours before they reach a coast
38
What are tsunamis often preceded by
A withdrawal of the sea at this stage there may still be time to escape by running or driving inland or uphill
39
Examples of tsunamis warning systems
PTWS NEAMTWS IOTWS CARIBE-EWS
40
What can dart bouys do
Detect the difference between long wave lengths of tsunamis and short of wind driven. If they confirm it the watch becomes a warning and triggers emergency response
41
Example f the national tsunami warning centre
Earthquake Calculate epicentre and magnitude - issue bulletin. If 6.5: Check sea level data is tsunami is generated. If yes confirm warning. Danger? If yes national emergency responses
42
What does dart bpr stand for
Deep ocean assessment and reporting of tsunamis. Bottom pressure recorder
43
What does PTWS stand for
Pacific Tsunami Warning System
44
What does the PTWS cover
28 countries, control centre in Honolulu Hawaii - 15 staff.
45
What happens during the PTWS
Global seismograph network detects potentially tsunamigenic earthquakes (usually submarine, shallow affects deformation of sea bed, M>7.5) Dart buoys used. Alert vulnerable communities so emergency plans can be activated.
46
How long does it take to analyse data and issue warnings
10-20 minutes: means blind zones for tsunamis generates close to the coast
47
What does TWS mean
Japanese Tsunami Warning System
48
How does the Japanese tsunami warning system work
Warning issued within 3 minutes of a tsunamigenic EQ. Quicker bc of dense coverage of equipment. Communities well prepared. Successful at reducing death toll. Highest risk by coast if tsunami is generated too close for warning to reach ppl.
49
Tsunami case study
Mw=9 megathrust EQ near Sumatra (Indonesia). Indian plate subducting under the Burma Microplate. 20m max displacement on the fault plane. Highest intensity (IX) felt in Banda Aceh, Sumatra. Resulting tsunami caused extreme destruction around Indian Ocean especially in Sumatra (run up 30m, inundation 1.5km). No warning system in place at the time. Subsequent funding put forward. 290,000 were killed. 1.1 million displaced by EQ and tsunami.
50
What are three other notable tsunamis
Aegean Sea - 1500 BC. Indonesia - 1883. Japan - 2011.
51
What was the cause and effects of the Aegean Sea tsunami
Cataclysmic eruption of Santorini. | Demise of advanced Minoan civilisation on Crete (source of Atlantic legend).
52
What was the cause and effects of the Indonesia tsunami
Cataclysmic eruption of Krakatoa. | Up to 35m run up. 36,700 killed
53
What was the cause and effects of the Japan earthquake
Me= 9 megathrust earthquake. | Up to 40m high run up, 20,000 killed.

Natural Hazards (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions