Seismic Hazards

Question 1

How deep is a shallow focus?

Answer 1

0-70km

Question 2

How deep is an intermediate focus?

Answer 2

70-300km

Question 3

How deep is a deep focus?

Answer 3

300-700km

Question 4

How is an earthquake measured?

Answer 4

Richter scale or Mercalli scale

Question 5

What are the primary effects of earthquakes?

Answer 5

Ground shaking

Ground rupture - visible breaking and displacement of the earths surface

Question 6

What are the primary effects of earthquakes?

Answer 6

Soil liquefaction - violently shaken soil with high water content lose their mechanical strength and behave like a liquid
Landslides/avalanche
Tsunamis
Fires

Question 7

What is the width and height of a tsunami?

Answer 7

Very long wave length - over 100km
Low wave height - under 1 metre
(When reaching shallow water bordering land they increase rapidly in height - excess of 25m)

Question 8

What is the speed of a tsunami?

Answer 8

700km/h

Question 9

How do people know a tsunami is approaching?

Answer 9

The wave trough in front of the tsunami results in a reduction in sea level, known as a drawdown.

Question 10

What do the effects of a tsunami depend on?

Answer 10

The height and distance travelled of the waves
Length of event
Extent of warnings
Coastal physical geography
Coastal land use and population density

Question 11

What caused the 2004 Boxing day tsunami in Sumatra?

Answer 11

9.0

25km shallow epicenter

Question 12

How many people were killed in the 2004 Boxing day tsunami in Sumatra?

Answer 12

300,000 people

Question 13

What were the main effects of the 2004 Boxing day tsunami in Sumatra?

Answer 13

Damage to infrastructure and economies

Cost less than $5 bilion

Question 14

What was the response to the 2004 Boxing day tsunami in Sumatra?

Answer 14

A warning system was set up among countries in the Indian Ocean

Question 15

What caused the 2011 Japan tsunami?

Answer 15

70km offshore earthquake with a magnitude of 9

Question 16

What was the effects of the 2011 Japan tsunami?

Answer 16

16,000 deaths
6,000 injuries
127,000 buildings destroyed
$235 billion cost

Question 17

How can we predict a seismic hazard?

Answer 17

Areas at risk can be identified through plate tectonics
Monitoring groundwater levels
Release of radon gas
Animal behaviour
Close studies of fault lines can often indicate next earthquake (studies of san andreas showed a seismic gap in Loma prieta)

Question 18

How can we prevent a seismic hazard?

Answer 18

Studies into lubricating the movement between the plates so that they don’t get stuck and cause an earthquake
But it’s almost impossible to prevent a seismic hazard

Question 19

How can we protect against a seismic hazard?

Answer 19

Hazard resistant structures
Education (e.g. disaster prevention day - drills)
Preparing emergency services
Land use planning
Insurance
Tsunami protection

Question 20

What is tsunami protection?

Answer 20

Automated systems to give warnings
Pressure sensors under buoys to measure the pressure under the water
Warning systems like klaxons

Question 21

How can we make hazard resistant structures?

Answer 21

-Large concrete weights on top of buildings which moves in the opposite direction to the force of the earthquake to counteract the stress
-Rubber shock absorbents in the foundations
-Cross bracing to the structure to hold it together better
Older buildings can be retrofitted

Question 22

What was the cause of the Haiti 2010 earthquake?

Answer 22

7 magnitude
13km epicenter
25km west of Port-au-Prince

Question 23

What was the risk and vulnerability of the Haiti 2010 earthquake?

Answer 23

Port au prince lies on the junction of the North American and Caribbean plates
Experienced several storms prior to the earthquake causing damage and 800 deaths
Poorest country in the western hemisphere

Question 24

What were the major effects of the Haiti 2010 earthquake?

Answer 24

160,000 deaths
300,000 injuries
250,000 houses destroyed
Vital infrastructure destroyed (meaning it was harder to reach injured people)
All hospitals in Port au Prince were destroyed
Damage to communications
Education system collapsed - 1,300 schools destroyed
Spread of disease - over 8,000 died in a cholera outbreak

Question 25

What were the responses to the Haiti 2010 earthquake?

Answer 25

US government deployed 3,500 soldiers

UK - search and rescue team with dogs to look for survivors

Question 26

How much has Haiti recovered from the 2010 earthquake?

Answer 26

Effects are still obvious;
over 170,000 people are still displaced
23% of children are not back in schools
70% lacked access to electricity
600,000 still food insecure
Costed $8 billion

Question 27

What caused the Christchurch 2011 earthquake?

Answer 27

6.3 magnitude
10km southeast from centre of christchurch
Depth was 5km

Question 28

What was the risk and vulnerability of the Christchurch 2011 earthquake?

Answer 28

Lies on the pacific ring of fire - geologically active
Fatalist approach
But shouldn’t have been that bad because the housing is single storey, low density, and the building regulations are very strict.

Question 29

What were the effects of the Christchurch 2011 earthquake?

Answer 29

185 dead - 115 of which died in the Canterbury Television building which collapsed and sent fire
7,000 treated for injuries
1,000 houses destroyed
Harbour facilities at Lyttleton were damaged
Soil liquefaction - areas could not be built upon and some suburban areas were flooded
Tasman glacier dislodged ice and fell into lake - tsunami in lake over 3m high

Question 30

How much has Christchurch recovered from the 2011 earthquake?

Answer 30

Almost completely and improvements were made but it will take New Zealand’s economy at least 50 years to recover from the costs