Lecture 3

Question 1

Tsunami is Japanese for:

Answer 1

harbour wave

Question 2

How are Tsunamis produced?

Answer 2

by the sudden displacement of water

Question 3

Events capable of triggering tsunamis:

Answer 3

• earthquakes that cause uplift of the seafloor
• landslides
• volcano flank collapse
• underwater volcanic eruptions
• meteorites

Question 4

What earthquake caused the greatest human casualties?

Answer 4

Sumatra Earthquake, Indonesia 2004

Question 5

Earthquakes can cause tsunamis in two ways:

Answer 5

1. By displacement of the seafloor

2. By triggering a landslide that enters water

Question 6

An earthquake must be at least ______ in order to trigger a tsunami

Answer 6

M 7.5

Question 7

Describe the stage 1 of the 4-stage process of a Earthquake-Triggered Tsunami Development

Answer 7

Stage 1: Displacement of the seafloor sets waves in motion that transmit energy upward and outward

• when the waves reach the surface of the water, they spread outward

Question 8

Describe the stage 2 of the 4-stage process of a Earthquake-Triggered Tsunami Development

Answer 8

Stage 2:
The waves move rapidly across the open ocean (can reach speeds of over 500km/h)

The spacing of the wave crests are very large (can be more than 100km)

The height (amplitude) of the waves is often small (less than 1 m)

Passengers on ships in the ocean rarely even notice tsunamis passing beneath them

Question 9

Describe the stage 3 of the 4-stage process of a Earthquake-Triggered Tsunami Development

Answer 9

• As the tsunami approaches land, the water depth decreases
• This results in the water ‘piling up’ and causes these effects:

1. a decrease in wave speed
2. a decrease in spacing of the waves
3. an increase in wave amplitude

Question 10

Describe the stage 4 of the 4-stage process of a Earthquake-Triggered Tsunami Development

Answer 10

• As the tsunami impacts land, waves can reach heights of dozens of metres
• the wave speed at this time can be up to 50km/h making them impossible to outrun

Question 11

Tsunami Event:

Answer 11

consists of a series of large waves reaching shore that can last for several hours

Question 12

Run-Up:

Answer 12

The maximum vertical distance that the largest wave of a tsunami reaches as it travels inland

Question 13

Types of Tsunamis

Distant Tsunami:

Answer 13

A tsunami that travels thousands of kilometres across the open ocean

On remote shorelines across the ocean, reduced energy lessens its impact

Also called tele-tsunamis

Question 14

Regional tsunami:

Answer 14

A tsunami that affects shorelines 100km to 1000km from its source

Question 15

Local Tsunami:

Answer 15

A tsunami that affects shore lining within 160 km from its source. They are the most dangerous types

Question 16

What Regions are most at Risk?

Answer 16

• coasts located near subduction zones or across oceans from subduction zones
• areas at greatest risk are the Pacific Ocean and the Mediterranean Sea

Question 17

Primary Effects of Tsunamis:

Answer 17

• Flooding and erosion destroy beaches, coastal vegetation and infrastructure
• After the tsunami retreats to the ocean, scattered debris is left behind
• most tsunami deaths are from drowning, injuries result from physical impacts with debris

Question 18

Secondary Effects of Tsunamis:

Answer 18

These are effects that generally occur after the event is over

• fires may develop due to ruptured gas lines or from ignition of flammable chemicals
• water supplies may become contaminated and water-borne diseases (cholera) may spread

Question 19

Indian Ocean Tsunami 2004

Answer 19

• source was a M 9.1 earthquake off the west of coast Sumatra
• 3rd strongest earthquake in world history

Question 20

Tsunameters

Answer 20

Sensors electronically connected to buoys verify that a tsunami was produced
- they rest on the seafloor and measure changes in water pressure passing over them

Question 21

Inundation Maps

Answer 21

showing the geographic area that can be potentially impacted by tsunamis are created to help plan for future events

Question 22

Prospect Theory

Answer 22

people are more willing to protect against a loss than gamble for an equivalent gain

Question 23

Cultural Adjustment

Answer 23

may result from changes in an environment

Question 24

Purposeful Adjustment

Answer 24

is specifically designed to reduce loss or damage

Question 25

Incidental Adjustment

Answer 25

not primarily hazard-related but they have the effect of reducing potential loss