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Tectonics > Unit 3 Notes > Flashcards

Unit 3 Notes Flashcards

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1
Q

What is the Focus?

A

The point of fracture within the crust.

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2
Q

What is the Epicentre?

A

The point of the earth’s surface located directly above the focus.

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3
Q

How can Seismic waves be measured?

A

By seismograms on a seismograph.

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4
Q

How is magnitude classified?

A

According to the Richter Scale.

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5
Q

What does 1 mean on the Richter scale?

A

Slight ground vibrations undetectable by humans.

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6
Q

What does 6 mean on the Richter scale?

A

Weak buildings damaged, walls and chimneys fall.

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7
Q

What does 8.5 mean on the Richter scale?

A

Total destruction waves seen in the ground.

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8
Q

What is the Modified Mercalli scale?

A

A scale of qualitative or descriptiveness.

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9
Q

What are the three main types of Earthquake waves?

A

P waves, S waves, Surface waves.

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10
Q

What are P waves?

A

Pressure waves - push and pull the rock, rapidly send pulses of vibration ahead.

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11
Q

What are S waves?

A

They vibrate the rock from side to side, perpendicular to the motion of travel. S waves travel slower - most rocks are weaker.

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12
Q

What are Surface waves?

A

Slower but larger, roving twisting motions. Side to side, up and down, 95% of seismic energy is released in the first 10 seconds. Buildings are most vulnerable to surface waves.

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13
Q

What are the stages of building collapse?

A

P waves cause ground to go up and down, S waves cause the ground to go back and forth, love waves undulate the ground laterally, Rayleigh waves make the ground surface roll in wave like motions.

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14
Q

What is Liquefaction?

A

Soft wet sediments are shaken by earthquake waves, the ground liquefies, causing buildings to subside.

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15
Q

What are the first three steps of Liquefaction?

A

Sediments shaken by seismic waves, seismic waves amplify in soft unconsolidated sediments, water saturated sediments compact.

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16
Q

What are the final three steps of liquefaction?

A

Water forced upwards, water and sediment erupt onto surface. Softened ground surface causes buildings to subside.

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17
Q

What are the secondary hazards of earthquakes?

A

Liquefaction, Tsunamis, Landslides.

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18
Q

What is the main primary hazard of an earthquake?

A

Ground shaking.

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19
Q

What are the main causes of Tsunamis?

A

Landslides - Into the ocean. Large earthquakes, volcanoes.

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20
Q

How do earthquakes cause Tsunamis?

A

Convergent plate boundaries where subduction occurs. Overriding plate experiences elastic rebound - the plate is flipped back up, then forced down.

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21
Q

How fast can the wave pass through deep ocean water?

A

6-900km per hour.

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22
Q

Why does wave height increase when the wave approaches the shore?

A

Friction on the sea bed reduces wave velocity, reduces wavelength, increases wave height.

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23
Q

What are the case studies of earthquakes with Tsunamic?

A

Japan 2011, Indian Ocean 2004.

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24
Q

What were the Characteristics of the Japan 2011 earthquake?

A

Magnitude 9, Tsunami flooded more than 200 square miles of coastal land, 38 metre high waves, $360 Billion of damage.

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25
What were the impacts of the Japan 2011 earthquake?
Nearly 20,000 people, more than 90% of deaths were from the Tsunami. Failure of Fukushima nuclear power station.
26
What were the Characteristics of the Indian Ocean 2004 earthquake?
Magnitude 9.1, 30 metre Tsunami in Banda Aceh.
27
What were the impacts of the Indian Ocean 2004 earthquake?
Nearly 230,000 people died, 2 million people made homeless. 13 countries affected.
28
How does ground shaking lead to increased risk of landslides?
More ground shaking means a higher likelihood of a landslide.
29
How does steepness of slope lead to increased risk of landslides?
Steeper slope means a landslide is more likely to occur.
30
How does saturation of soil increase the risk of a landslide?
More water saturation means higher risk of a landslide - increased friction.
31
How does land use affect the risk of a landslide?
Deforested land is more prone to landslides.
32
What are the case studies of earthquakes with landslides?
2008 Wenchuan earthquake, China. 2005 Pakistan earthquake.
33
What were the characteristics of the Wenchuan earthquake?
7.9 Magnitude, Monsoon rains caused hillslopes to slide downslope.
34
What were the impacts of the 2008 Wenchuan earthquake?
Over 80,000 earthquake-triggered landslides and mud flows. One single mudflow killed over 200 people.
35
What were the Characteristics of the 2005 Pakistan earthquake?
7.6 Magnitude, landslides blocked roads and destroyed telephone lines, resulting in delayed responses.
36
What were the impacts of the 2005 Pakistan earthquake?
85,000 dead, 2500 landslides triggered. Landslides were responsible for 26500 deaths. 3.5 million left homeless.
37
What were the Characteristics of the 1989 California earthquake?
5pm, 6.9 Magnitude, Conservative plate boundary, 2 million population.
38
What were the Characteristics of the 2010 Haiti Earthquake?
5pm, 7.2 Magnitude, Conservative plate boundary, 2 million population.
39
What were the impacts of the 1989 California earthquake?
63 deaths, 3757 injured, 12000 homes damaged, $6.8 Billion damage.
40
What were the impacts of the 2010 Haiti earthquake?
0ver 220,000 deaths, Over 300,000 injured, Over 100,000 homes damaged, $7.8 Billion damage.
41
What were the similarities between the earthquakes in California and Haiti?
Both had the same plate boundary, similar magnitudes, same time of day.
42
What were the differences between the earthquakes in California and Haiti?
Much more extreme in Haiti - 220,000 deaths compared to 63. 300,000 injured compared to 3757. 100,000 homes damaged, compared to 12,000.
43
Where was the Epicentre in the 1989 California earthquake?
Close to urban areas of Santa Cruz, San Jose.
44
How was the Earthquake caused in California?
Caused by movement along the Conservative San Andreas fault line.
45
What were the secondary hazards of the California earthquake?
Liquefaction, Landslides.
46
How many of the deaths were due to Liquefaction in California?
42 out of 63.
47
What was the main area subject to Liquefaction?
The collapse of the two-level cypress freeway in Oakland.
48
How many vehicles travel along the freeway each day?
170,000.
49
How long did it take to rebuild the freeway?
Nine years, and $1.2 Billion dollars.
50
What was the Geology beneath the collapse section of the highway?
Sand and Gravel, soft - ejected water upwards, causing them to compact more. 50% of the highway was built on marshland.
51
What was the worst affected area from Liquefaction in San Francisco?
The marina district, which was built on landfill, made of a mixture of sand, rubble, and other materials.
52
What was the impact of landslides?
More than 1000 landslides occurred around the epicentral zone in the Santa Cruz mountains.
53
How is San Francisco preparing for the next earthquake?
New tall buildings are being built to withstand earthquakes, as they're more flexible, and can sway. It's now mandatory to retrofit certain structures. Water and gas supply now has increased protections.
54
How is San Francisco not prepared for the next earthquake?
Many buildings are built on landfill, which could increase risk of liquefaction. Only 1 in 10 Californians have earthquake insurance, as homes are very expensive in the area.
55
What is the poorest nation in the Western Hemisphere?
Haiti.
56
What were the short term impacts of the Haiti Earthquake?
80% of buildings collapsed or were seriously damaged, including the presidential palace.
57
Which human factors contributed to the Haiti Earthquake?
Building design, land use planning, community preparedness, emergency services.
58
How did Building design contribute to the Haiti Earthquake?
86% of the population of Port Au Prince were living in tightly packed slum conditions, housing was of very poor quality with little aseismic design. Not enough reinforcing steel rods.
59
How did Land use planning contribute to the Haiti Earthquake?
There was no planning to take into account earthquakes. Crowded conditions meant that when buildings collapsed, there was rubble in the streets which hindered movement and rescue.
60
How did Community preparedness contribute to the Haiti Earthquake?
80% of the schools were of poor quality. Literacy levels were poor. Most people had received little or no earthquake training, didn't know what to do when the quake struck.
61
How did Emergency and relief services contribute to the Haiti Earthquake?
Many of the hospitals were destroyed or badly affected by the quake. Emergency services weren't sufficiently trained to deal with crisis. Airport damage meant emergency flights were unable to bring assistance.
62
What were the social impacts of the Haiti Earthquake?
60% of government buildings were destroyed. 80% of schools in Port au Prince were damaged. 1100 temporary camps were opened for homeless people. Disease outbreaks leading to Cholera, leading to 12,000 additional deaths.
63
What were the negative economic impacts of the Haiti Earthquake?
$7.8 Billion of damage, 120% of 2009 GDP. $2.3 Billion cost of rebuilding homes. Unemployment rose to 75%.
64
What were the positive economic impacts of the Haiti Earthquake?
$3.5 Billion was given in foreign aid, the EU gave $330 Million. The world Bank waived Haiti's debt repayment for 5 years. Western governments sent over 1000 military and disaster relief personnel.
65
Why has Haiti not recovered fully?
Much of the funds never reached Haiti - more than $13 Billion was given, but only 48% made it to Haiti - a lot went to organisations that aren't in Haiti. A lot of people left the country to go to other countries.
66
What were the impacts of the 2021 Haiti earthquake?
Almost 1300 died. The epicentre was 150 miles south of PAP. Almost 6000 injured. Routes to emergency centres were blocked, due to control of roads by gangs.
67
How have natural disasters contributed to political crises in Haiti?
The president was shot and killed 1 month after the 2021 earthquake, and another earthquake occurred during the investigation. The natural disaster meant the government didn't have the capacity to respond to keep order on the streets.
68
What were the facts of the Turkey 2023 earthquake?
3 earthquakes, from 6.4-7.8 magnitude. Over 7000 buildings collapsed, over 200,000 buildings damaged.
69
Why did so many buildings collapse in Turkey?
Lack of oversight from the government, they allowed some buildings to be built which shouldn't have been. Many buildings had soft story designs, which are particularly vulnerable to earthquakes.

Tectonics (4 decks)

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