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Geography A Level > A. Earthquakes and Tsunamis > Flashcards

A. Earthquakes and Tsunamis Flashcards

1
Q

What are earthquakes caused by?

A

Earthquakes are caused by the release of friction from the movement of tectonic plates. This often occurs at a zone of weakness within the existing rock.

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2
Q

What is Intensity?

A

Intensity is the severity of earthquake shaking, measured on the Modified Mercalli Intensity Scale. This is determined from effects on people, human structures and natural environment.

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3
Q

What is Magnitude?

A

Magnitude is the amount of seismic energy released from an earthquake, measured on the Richter Scale

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4
Q

What is a seismograph?

A

A seismograph is an instrument used to record the motion of the ground during an earthquake

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5
Q

What are Aftershocks?

A

Aftershocks are subsequent movements, often less violent, following a major earthquake.

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6
Q

What are the general hazards of earthquakes?

A
  • Ground shaking - horizontal and vertical
  • Tsunamis
  • Movement of crust - lateral and vertical
  • Fires
  • Liquefaction
  • Landslips / landslides
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7
Q

What is liquefaction?

A

Liquefaction is when an earthquake shakes saturated sediments, causing water to rise to the surface and turn the soil into liquid mud

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8
Q

Where is liquefaction common?

Where does liquefaction not occur?

A

Liquefaction is common in loose, granular sediment where there is saturation by groundwater.
This is especially common in reclaimed coastal land i.e. land that was formally mud flats / saltmarsh

Liquefaction does not occur in solid rock

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9
Q

Give two examples of events with liquefaction:

A
  • 1995 Kobe earthquake - reclaimed land in port and harbour
  • 1989 San Francisco earthquake on reclaimed land in harbour
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10
Q

What are the properties of P Waves?

A
  • Longitudinal waves - motion of particle is parallel to direction of wave
  • Body wave
  • Passes through solids and liquids
  • Faster than S waves
    [Fastest wave]

(Think - push waves!)

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11
Q

What are the properties of S Waves?

A
  • Transverse waves - motion of particle is perpendicular to direction of wave
  • Body wave
  • Can only pass through solids
  • Slower than P waves

(Think - shake waves!)

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12
Q

What are Rayleigh Waves?

A
  • Circular motion - created by a combination of transverse and longitudinal waves
  • Most destructive waves
  • Surface wave
  • Can only pass through solids
  • Slower than S waves (travel at 80-90% of their speed)
    Speed = ~7800mph [Slowest wave]
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13
Q

What are Love Waves?

A
  • Largest amplitude - largest AOE
  • Surface wave
  • Can only pass through solids
  • Slightly faster than Rayleigh waves
    Speed = ~10,000mph
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14
Q

What was the date of the Türkiye-Syrian Earthquake?

A

6th February 2023

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15
Q

How intense was the earthquake and its aftershocks?

A

Primary earthquake magnitude: 7.8 Richter Scale
Aftershock magnitude: 7.5 “

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16
Q

Which movement / plates were involved in the Türkiye-Syria Earthquake?

A

Conservative plate movement
Arabian and Anatolian plates at the Anatolian Fault

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17
Q

What were the primary hazards of the 2023 Türkiye-Syria Earthquake?

A
  • Initial earthquake caused a 300km surface rupture, one of the largest inland ruptures globally
  • Vertical displacement reached 11.4m at eastern end
  • Second earthquake that day resulted in an additional 125km of rupture
18
Q

What were the secondary hazards of the 2023 Türkiye-Syria Earthquake?

A
  • Liquefaction occurred in former lake beds, rivers and coastal areas, primarily at the southern end of the East Anatolian Fault → ground failure and lateral spreading
  • Seawater incursion at Iskenderum of up to 200m inland - minor tsunami 12cm high
19
Q

What were the primary impacts of the 2023 Türkiye-Syria Earthquake?

A

Disaster affected nearly 18 million people in Türkiye and Syria

  • 55,000 deaths and 130,000 injuries
  • Fifth deadliest earthquake of the century
  • Millions of people displaced - 2.6 million accommodated in tent cities and another 1.6 million residing on the streets outside their damaged, unsanitary and unsafe homes.
  • ~300,000 buildings, including residential apartments, schools, hospitals and roads were destroyed or rendered unusable.
20
Q

What were the secondary impacts of the 2023 Türkiye-Syria Earthquake (excluding mental health)?

A
  • Earthquake ranks as third costliest of the century globally, accounting for 9% of Türkiye’s GDP. [Social and Economic Effects]
  • Disruption to roads leading to rural areas devastated agricultural livelihoods and production, resulting in short term food shortages and long-term disruption to family incomes.
  • Water pipes / sewage works are destroyed by the earthquake increasing risk of contagious water-borne diseases such as cholera, especially considering conditions in temporary shelters
  • Only 1 in 7 health centres were partially functioning, preventing those with pre-existing conditions from receiving necessary treatment.
21
Q

What were the secondary impacts of the 2023 Türkiye-Syrian Earthquake on mental health?

A
  • Tens of thousands of survivors traumatised by disaster, dealing with the loss of loved ones, homes and livelihoods.
  • Long-term investment into mental health services will be required for individuals to recover.
  • In the affected area, 5.4 million children are at risk of developing anxiety, depression and PTSD.
22
Q

How did winter weather affect the scale of the disaster?

A
  • High-pressure system over Europe trapped cold air over the Middle East - clear daytime skies led to very cold nights, 5-10’C lower than on average, affecting survivors reluctant to return to enter still standing buildings.
  • Heavy rainfall in March 2023 caused flooding which destroyed temporary shelters such as tents and cars
23
Q

How did the time of day affect the scale of the disaster?

A
  • The earthquake occurred at 04:17, when the majority of the population was asleep, resulting in a high death toll as more people were in buildings.
24
Q

How did a large child population affect the scale of the disaster?

A
  • Children are particularly vulnerable to waterborne diseases such as cholera and hepatitis, as well as hypothermia due to lack of shelter.
  • Prior to the earthquake there were 130,000 pregnant women in the area, and 14,000 births were registered in the first month after the earthquake. This rose to 24,000 after 2 months.
  • 47% of the Syrian refugees are under 18
25
Q

How did the Syrian civil war affect the scale of the disaster?

A

3.6 million Syrian refugees reside in SE Türkiye, making it the largest host country for refugees globally.

In NW Syria, 3 million internally displaced refugees face increasing challenges with few resources to rely on.

  • Only 5% of Syrian refugees live in camps
  • 90% of all Syrian refugees live below the poverty line
26
Q

What had Türkiye done to prepare for earthquakes?

A

Izmit Earthquake 1999 killed 17,000 people, ingrained in national memory - introduction of building regulation as well as school earthquake drills.

Turkish president Recep Tayyip Erdoğan said after the 2023 earthquake that it was ‘impossible to prepare for the scale of the disaster.

27
Q

What were the responses to the 2023 Türkiye-Syria Earthquake?

A
  • Immediate response from the Turkish government was slow and uncoordinated, taking 36 hours to deploy the military
  • UN sent search and rescue teams as well as raising £1.25bn through an appeal to help those affected.
  • World Health Organisation sent health supplies to Syria and Türkiye, helping 400,000 people
28
Q

What challenges prevented adequate aid from eaching affected areas in Syria?

A
  • No coordination between factions in Syria
  • UN food programmes reported Kurdish led Syrian democratic forces were blocking access for aid to areas in Northern Syria
  • Syrian dictator Bashar al-Assad had to be convinced to open additional border crossings for aid
29
Q

How did the areas affected by the 2023 Türkiye-Syria Earthquake recover?

A

After the earthquake, 1.5 million people were left homeless - the government plans to construct 500,000 new housing units to solve the homelessness crisis within a year. As of June 2023, 134,000 were under construction.

Engineers agree that if Türkiye’s building regulations are followed, new construction will be very earthquake resilient

  • UN Program supported the Turkish government in the cleanup of 100 million m3 of debris.
30
Q

What mitigation strategy does the Turkish government have to reduce the effects of earthquakes?

A

Very limited strategy - Türkiye has no earthquake monitoring or protection system

  • Turkish officials had not been enforcing building regulations - 345,000 apartments were destroyed
  • Government allowed builders to pay ‘amnesty’ to receive an officially sanctioned breach of regulation.
31
Q

What natural disasters can potentially cause tsunamis?

A

Tsunamis are created by:

  • Earthquakes (as a secondary hazard)
  • Landslides falling into water e.g. from a collapsing volcano / underwater landslides
  • Pyroclastic flows entering the sea
32
Q

Where do tsunamis mostly form?

A
  • Majority form in subduction zones
  • 90% are formed in the Pacific basin
  • Generated in deep-sea trenches e.g. by Japan, Aleutian, Peru-Chile trench
  • 1/3 of all tsunamis created in deep trenches around Japan
  • Not all underwater earthquakes create a tsunami - most form from earthquakes with a shallow focus and a high magnitude (6.5+)
33
Q

What are the characteristics of a tsunami?

A
  • Typically have a huge wavelength (up to 100km) and a low amplitude (0.5m)
  • Speeds of 700km/hour
  • As the wave approaches land and the water becomes shallower, the wave will bunch up / shoal to become taller
  • Typical height upon approaching land is 2-3m
34
Q

How tall was the 1883 Krakatoa tsunami?

A

35m high

35
Q

How many people were killed by the 1883 Krakatoa tsunami?

A

36,000

36
Q

What was the magnitude of the earthquake that caused the 2004 Boxing Day tsunami?

How tall was the tsunami as it travelled across the Indian Ocean?

A
  • Magnitude 9.2 earthquake in Sumatra
  • 10m high
37
Q

How many people were killed by the 2004 Boxing Day Tsunami?

A
  • 224,000 - 400,000 killed in 18 countries
  • 93 British victims (mostly holidaymakers)
38
Q

Who was warned about the 2004 Boxing Day tsunami?

A
  • Although the tsunami took two hours to reach Thailand, there was no warning system in place
  • The earthquake and tsunami threat was picked up by tsunami warning HQ on Hawaii, but they had no means of getting a message to such a huge number of possible victims.
39
Q

How strong was the Sendai Earthquake of March 11 2011?

A
  • Magnitude 9 earthquake
  • Subduction zone lurched up as much as 10m
40
Q

How large was the tsunami from the Sendai Earthquake of March 11 2011?

A
  • A 10m high wave hit Sendai and penetrated 6km inland
  • Wave travelled 8000km/hr across Pacific, reaching a height of 3.5m at Hawaii and 3m at Antartica.

In Antartica, ↑ caused part of the Sulzberger ice shelf to break off

41
Q

What were the impacts of the Sendai Earthquake of March 11 2011?

A
  • 20,000 people killed
  • Meltdown of Fukushima nuclear power station

Geography A Level (33 decks)

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