Tectonic Hazards

Question 1

Continental Crust

Answer 1

Can be between 10 and 70km thick. It is old and granitic with a high aluminium content. More buoyant than oceanic crust (density of 2.6 au) so does not subduct.

Question 2

Oceanic Crust

Answer 2

Newer, denser (3.0au) and with a greater magnesium content. Basaltic rather than granitic. Is 7km thick and consistently so.

Question 3

Lithosphere

Answer 3

Top of the mantle and bottom of the crust. This is where the friction that leads to the slab pull effect happens.

Question 4

Asthenosphere

Answer 4

A 630km thick zone of semi-molten mantle. This is a low velocity zone for seismic waves. Temperatures range from 500 - 1000 deg C. Below Lithosphere, above Mesosphere.

Question 5

Mesosphere.

Answer 5

2200km thick zone of Magma with temperatures of between 1000 and 4000 deg C. More dense than the Asthenosphere above it, it is a higher velocity zone for seismic waves.

Question 6

Outer Core

Answer 6

2260km thick zone. It is comprised not of molten rock but of molten iron and nickel given its high temperature (between 4000 and 5000 deg C).

Question 7

Inner Core

Answer 7

Temperatures range between 5000 and 6000 deg C but, because of the high pressure it is under, it is a solid ball of Iron.

Question 8

Plate Movements

Answer 8

This occurs as a result of a phenomenon called Slab Pull. Superheating from the core causes magma in the mesosphere to well up (usually aided and abetted by radioactive decay in the outer core). When it reaches the surface, save for some outward effusion at constructive boundaries, it cannot move vertically and has to move laterally. It undergoes friction with tectonic plates in the lithosphere and - as a result - pulls these by SLAB PULL.

Question 9

Initial Theory of Continental Drift

Answer 9

Bacon in 1620 first proposed that the current world map may not have been constant for all of history. He noted the seemingly complementary shape between S America and Africa.

Question 10

Alfred Wegener

Answer 10

Working in 1912 he drew up maps showing how one supercontinent (Pangaea) split up into two smaller continents (Gondwanaland and Laurasia) which then split into the continents we know today. These maps hold up but Wegener could not get support for his theories as he did not understand the plate tectonics behind what was happening.

Question 11

Contour Evidence

Answer 11

Edward Bullard (Cambridge; 1965). Used early computer modelling to show that, at the 1000 click contour level both S America and Africa and N America and Europe fit together perfectly suggesting that they broke apart.

Question 12

Geological Evidence

Answer 12

The same granite is found in the Cambrian Mountains in NW Europe and the Appalachian Mountains in the NE United States. Similar findings in precambrian rocks in S America.

Question 13

Climactic Evidence

Answer 13

When we apply the present climatic map to the Wegener maps we can explain some anomalies. Coal, found in Antarctica, formed in warm wet swamps 300 MYA. In contrast, glacial features (formed only in high latitudes and altitudes) can be found in warm areas of India and Africa.

Question 14

Paleontological Evidence

Answer 14

Glossopteris spp. ferns were found in S America, Africa, India, Australasia and Antarctica. These areas must have been connected as there is no way that the fern could have migrated all of this way.

Question 15

Palaeomagnetism

Answer 15

Ferrite formed in newly erupted rocks acts like a small bar magnet. It aligns itself with the poles. When the ferrite was examined it appeared that there was some polar wander. This cannot happen as the poles only flip every so often (which was also clearly evidenced). It was deduced that if the poles were not moving then the rock was moving relative to it, as it would be in sea floor spreading at constructive margins.

Question 16

Vine and Matthews

Answer 16

Their work showed that the ferrite aligned to the shifting poles. This demonstrated that the process of sea floor spreading was continuous.

Question 17

Hess and Dietz

Answer 17

US WW2 submarine commanders. Using Sonar they mapped the mid-atlantic ridge. This gave support to the theory of ridge formation when sea floor spreading occurred.

Question 18

Pressure Drive

Answer 18

Pressure within the mantle builds up as melting in the Benioff zone adds molten rock in. This pressure is released at hotspots and constructive margins (+ volcanoes at destructive ones) when rock is given an impetus to move upward by radioactive decay in the outer core.

Question 19

Constructive Margins (Subsea)

Answer 19

Ocean ridge formation as the sea floor spreads apart and magma upwells to create the valley bottom. When two parts of the ridge move at different speeds the profile of this is different and transform faults (relatively small cracks perpendicular to the main ridge axis) are formed.

Question 20

Slow Rate Constructive Margins

Answer 20

Move apart by 10-15mm per year. The Mid Atlantic Ridge is an example of this. There is a deep, central rift valley. The ridge tends to be between 30 and 50km wide. Sometimes undersea volcanoes can erupt above the surface forming Islands like Surtsey, off Iceland.

Question 21

Mid Atlantic Ridge

Answer 21

Is 16,000 km long and 1000km wide. Its average depth is 2.5 km but off the Icelandic coast it is 4km deep. It can be seen on land in the Thingvellir national park - Iceland.

Question 22

Medium Rate Constructive Margins

Answer 22

50-90mm per year. Here, upwelling is sufficiently quick that just a 50-200m crack is seen in the ocean floor surface. This is seen at the Galapagos Pacific Ridge forming the well known island chain.

Question 23

Fast Rate Constructive Margins

Answer 23

Spread at over 90mm per year. A convex domed crest is seen atop them such as at the South Pacific Rise.

Question 24

Rift Valley Formation

Answer 24

A superheated, radioactive-decay fueled plume of magma will well up through the mantle. It pushes the rock above it up at a central point, stretching it to the brink of its elasticity at which point multiple fracturing occurs as it snaps. A central block of rock (called the Horst) is formed with staggered fault scarps descending each side. Some of these faults can become magma tubes, seeing volcanoes (e.g. Mt Kilimanjaro). At each side, the rift valley that is formed is usually BSL so it can fill with water. This is a new plate boundary. One tends to undergo more spreading than the other. The horst is the point from which Victoria Falls falls.

Question 25

Great African Rift Valley

Answer 25

Runs 4000km from Mozambique to the Red Sea, continuing 1500km from there into Jordan. The Horst-Valley Bottom distance can be as much as 600m, giving the impressive freefall of Victoria Falls.

Question 26

Oceanic - Continental Convergence

Answer 26

Here, an oceanic plate subducts under a continental plate, bending the edge of the continental plate up (forming fold mountains through a process known as Orogenesis). Often, these mountains are also volcanoes (such as Mt St Helens).

Question 27

Oceanic - Oceanic Convergence

Answer 27

When one oceanic plate is subducted under another, it is the larger plate that is subducted. A marginal geosyncline is formed when sea floor sediment from the larger subducting plate collects in the trench formed. This can rise above the surface causing an accretionary island arc or at least act as an accretionary wedge, often forming a reef site. Behind this there will be a volcanic island arc above the zone of plate melting in the Benioff zone. Between these two arcs is a fore-arc basin.

Question 28

Ocean Trenches

Answer 28

Ocean trenches are often around 6000km deep. The Marianas trench, formed when the Pacific plate subducts under the Phillipines plate, is the world’s deepest at 11,000m. Islands formed by accretion and volcanic eruption when this happens include Guam and the Aleutian Islands.

Question 29

Continental-Continental Convergence

Answer 29

Here two relatively low density plates meet and no subduction happens. Instead, they crash together driving the sediment of the geosyncline up to form mountain peaks with metamorphic rocks at the top. Some rock is also forced down creating deep mountain roots triangular in shape. There are no volcanic eruptions as there is no subduction but there can be strong earthquakes such as the one which hit Sichuan, China in 2008.

Question 30

The Himalayas

Answer 30

This range of fold mountains was formed by continental-continental convergence when the modern day Indian subcontinent, on the Indo Australian plate, crashed into the Eurasian plate, obliterating the Tethys sea. This explains why sedimentary rocks are found atop Himalayan peaks. The range is 3000km long and 350km wide. It contains the world’s tallest mountain - Mt Everest - at 8848 m tall.

Question 31

Conservative Boundaries

Answer 31

e.g. San Andreas Fault, California. Again, there is no volcanic activity as there is no subduction. Very large earthquakes can result when the plates which move alongside each other at 4cm per year snag. Transform faults occur here as well and, in the San Andreas Fault System, are responsible for the regular smaller occurrences.

Question 32

Hotspots

Answer 32

These are areas of volcanic activity away from plate boundaries, often in the middle of plates. They are fueled by a superheated column/plume of magma which eats through the thin crust forming a series of shield volcanoes as the plate moves relative to the Hotspot.

Question 33

Emperor Seamount Chain

Answer 33

Responsible for the formation of the Hawaiian island chain. The plate moves to the NW over time and islands become dormant. Kauai contains rock 3.8 million years old while Maui contains rock 0.8 million years old. Hawaii itself is still volcanically active. In the future, the Liohi underwater volcano will erupt above the surface. The chain is 5000 km long, stretching to the NW away from Hawaii. The oldest seamounts are 70 million years old and have subsided under their own weight below the sea’s surface.

Question 34

Volcanic Explosivity Index

Answer 34

Measures volume of Tephra emission from a volcano. Gives no measure of violence of eruption or gas emission however.

Question 35

Basaltic Lava

Answer 35

Found at constructive boundaries and is of low viscosity due to its low silica content. It is alkaline in nature.

Question 36

Andesitic/Rhyolitic Lava

Answer 36

This is high silica, high ash content lava and as a result it is highly viscous, often clogging volcanic vents. Comes from destructive zones, being a product of melting in the Benioff zone.

Question 37

Fissure Eruptions

Answer 37

These are gentle and effusive with lava spilling persistently out of an open fissure. The lava coats the landscape giving a featureless Lava Plateaux. These can often be very large. The Deccan Plateau in NW India is comprised of 700,000 cubic kilometers of Lava from 29 major lava flows.

Question 38

Shield Volcanoes

Answer 38

A characteristic feature of hotspots. Basaltic lava here gently spills out creating a very shallow slope. These are exclusively below 10 degrees with some in Hawaii being only 2-3 degrees. The Island of Maui is 40,000 km3 in volume. It is 4170m ASL with a total height from top to bottom of 10,099m (taller than Mt Everest).

Question 39

Composite Volcano

Answer 39

Traditional volcanic cone shape. Common at destructive boundaries (Etna and Vesuvius in Italy). It is formed of alternating ash and lava layers. When it erupts, ash is erupted first because its lava is thick and andesitic. Has a 30 degree incline. Can have parasitic cones to each side.

Question 40

Acid/Dome Volcano

Answer 40

Rhyolitic lava is erupted explosively. It is so thick that it does not travel far when it erupts, cooling after having travelled only a short distance and therefore the volcano is extremely steep. e.g. Puy de Domes, France.

Question 41

Ash/Cinder Volcano

Answer 41

Rhyolitic lava. No lava is really erupted out as it blocks the vents. Ash produced first followed by cinders and volcanic bombs. These build up the cone.

Question 42

Caldera Volcano

Answer 42

When extremely rhyolitic lava blocks the vent a rapid and unpredictable explosion, usually accompanied by a pyroclastic flow, occurs creating a large crater as the summit of the volcano blows off. The body of the volcano is a mixture of the acid/dome and the ash/cinder types. It is in essence a special composite. If the explosion happens at sea level the crater can fill with water becoming a lagoon (this happened at Krakatoa, Indonesia). When this happens away from the sea the crater can fill with water (e.g. Crater Lake, Oregon).

Question 43

Boiling Mud

Answer 43

Steam and water mix with mud and soil to create pots of bubbling mud. Seen on the Reykjanes peninsula, Iceland.

Question 44

Solfatara

Answer 44

Sulphurous gasses mix with groundwater turning it into a pungent smelling steam that rises upward from the ground. Seen on the Reykjanes peninsula, Iceland.

Question 45

Geyser

Answer 45

Water in a fissure in the lower crust heated until it turns into a water and steam mixture which is then channeled up the fissure, erupting as a Geyser. Seen on the Reykjanes peninsula, Iceland.

Question 46

Fumarole

Answer 46

Solfatara+Boiling Mud

Question 47

Batholith

Answer 47

c. 300km wide mass of rock eating through neighbouring rock strata. Forms a metamorphic aureole where surrounding rock metamorphoses (granite into schist in Dartmoor). Rock runs out of the batholith as vertical dykes (horizontal cooling cracks) while veins called sills run off of these between rock strata (vertical cooling cracks like the batholith). Dykes and Sills made of Dolerite. Swarms of dykes form the Isles of Mull and Skye off Scotland. The most well known sill in the UK is Great Whin Sill upon which parts of Hadrian’s wall are built.

Question 48

Laccolith

Answer 48

Similar to a batholith but much smaller (metres not km) and as a result as opposed to eating through rock strata it forms in between them, displacing those above it upward. An example of a laccolith is Devil’s tower, Wyoming USA.

Question 49

Mount Etna

Answer 49

An active composite volcano on a destructive boundary. Its last notable eruption was in 2014. 25% of the population if the Island of Sicily live on its banks. Notable is the town of Zafferana in the Valle de Bove with a population of 8000. Many vineyards and citrus farms. In 1991, the GDP of Italy was $20,000. Current cone active for 170,000 years.

Question 50

Etna: Case Study Eruption

Answer 50

Erupted on 14th December 1991. The eruption lasted for 474 days. The lava was andesitic but notable fluid. 250 million m3 of lava was put out. It was a flank eruption, flowing down the SE side of the mountain toward the town of Zafferana. It was the largest eruption of Etna in 300 years.

Question 51

Etna: Impacts

Answer 51

Winemakers and farmers in the Valle de Bove saw crop losses. Local springs were destroyed. The town of Zafferana was unaffected, only 1 building on the outskirts was destroyed.

Question 52

Etna: Responses

Answer 52

In 1992 a 400m long, 20m high earth bank was built - in accordance with contingency plans - to stop the lava reaching Zafferana. This was overwhelmed after a month so the line was retreated and 3 separate, smaller barriers were built. The US Marines were brought in under ‘Operation Volcano Buster’. The intention was to destroy lava tubes that had allowed the Lava to run for 7 miles without cooling. This was done by dropping concrete blocks and explosives. The lava flow was stopped 850m from the town.

Question 53

Etna: Monitoring

Answer 53

The mountain is monitored by the Sicilian Institute of Vulcanology. It is volatile and unpredictable; in 2002 the ski station of Piano Provenza was destroyed and ash rained down on the Sicilian capital Catania.

Question 54

Soufriere Hills, Montserrat

Answer 54

N American plate is being subducted under the smaller Caribbean plate. Montserrat is a part of the resulting Volcanic Island Arc.

Question 55

Background to the Soufriere Hills eruption.

Answer 55

The volcano awoke in early 1995 having been dormant for 300 years. There were not many contingency plans. Volcano began steaming and the mud pots got hotter. On 18th July 1995 a VEI 3 eruption occurred. This was a pyroclastic event doing a lot of damage but, fortunately, killing nobody. The South part of the Island, however, was evacuated - including the capital, Plymouth - and made an exclusion zone.

Question 56

Continuation of the events in Soufriere Hills and fatalities.

Answer 56

Another large pyroclastic eruption occurred on 25th June 1997. The lava dome collapsed and 19 farmers who, with no alternative livelihood, had returned to the exclusion zone to tend their crops, died. This was a large eruption with 5 million m3 of Tephra produced.

Question 57

Volcano monitoring in Montserrat

Answer 57

Monitoring performed by the Montserrat Volcano Observatory. Collect GPS movements (to show lava dome movements); gas spectra (to see how much SO2 is being produced); seismographs (to see any LPE’s), and infrasound detections (to detect any degassing episodes).

Question 58

Impact on Population

Answer 58

The population before the event was an already diminished 10,000 (following people leaving after Hurricane Hugo in 1989). It bottomed out at 3000 in 1999 but a mixture of 1500 new arrivals from other parts of the Caribbean looking for work in construction and people returning it stabilised at 5000. Attaining a sustainable population is a major part of the island’s sustainable development plan.

Question 59

Health Impacts

Answer 59

PTSD a problem. Respiratory Silicosis also.

Question 60

Educational Impacts

Answer 60

School enrolment has decreased by 4.3x. A new community college was built in 2005 to try and reverse this. There was an offshore medical school, whose 400 students and staff were big spenders in the economy. This is now gone.

Question 61

Impact on Farmers

Answer 61

300 full time farmers were displaced. The island was once agriculturally self sufficient, a major lime producer. Now it is not. The government are trying to pilot the growing of papaya and sweet potato on fertile volcanic ash. Montserrat rice mills, once a major employer, is struggling as there is little rice left to mill.

Question 62

Government attempts to revitalise Montserrat

Answer 62

Voluntary donors have paid £3m to develop a new cultural centre. The government completed the first stage of the new capital project at Little Bay in 2010. They are building a new ash processing facility.

Question 63

International Aid Receipts

Answer 63

Receive £16.4m a year from the UK DfID. In 2004, the DfiD gave a £3m grant to build new tourist accommodation on the island. In 1997, only 4000 tourists came a year, climbing to 15,000 when a twice daily ferry link to Antigua was put in place. When this ended in 2005 (funding ran out) only 9500 people came a year in 2006. Volcano tourists put off as police unwilling to let people visit Plymouth.

Question 64

Energy Issues

Answer 64

Relies on unsustainable diesel generators. A 400kWh wind power scheme was piloted but scrapped as a result of a shortage of other suitable sites. Solar arrays impractical as a result of ash fall. A geothermal aquifer capable of delivering 2-5MW of power was found but its exploitation cannot be funded.

Question 65

Environmental Degradation

Answer 65

1/3 of rainforest destroyed. Endangered Mountain Chicken frogs attacked by feral dogs.

Question 66

Sustainability

Answer 66

£3000 in British aid per resident. It is unlikely ever to be economically sustainable.

Question 67

Armero Tragedy - Prediction

Answer 67

In 1984, having seen that 100 years ago a lahar flowed down two converging valleys, reaching the town of Armero and causing devastation, scientists from the Colombian Institute of Vulcanology recommended that - in light of new activity - the town of Armero be evacuated. The government refused to do this as they could not give a time scale.

Question 68

Armero Tragedy - Eruption

Answer 68

The volcano Nevado del Ruiz erupted late at night on the 13th November 1985. The lahars, formed as expected from the mountain top glacier melting, flowed down the valley and inundated the town of Armero. Of 30,000 occupants 25,000 were killed. The first contact with the outside world was when the press arrived 3 days after. Only then was aid summoned. 5000 superfluous deaths occurred.

Question 69

Prediction Hypotheses: Williams and Stix

Answer 69

They hypothesised that in the run-up to an eruption SO2 emissions would rise. They were proven catastrophically unreliable tools when Williams took a conference group into the crater of a Colombian volcano and it erupted on them.

Question 70

Prediction Hypotheses: Bernard Chouet

Answer 70

He analysed seismographs and noticed that waveforms called LPE’s (Long Period Events), which represented harmonic motion as lava moved up the lava pipes, increased in frequency before the volcano erupted. An analysis of this could have saved Williams’ party from their hideous injuries.

Question 71

Popocatepetl

Answer 71

In December 2000 Chouet’s LPE’s predicted that this eruption would occur. The Mexican government brought in 2000 soldiers who ensured the evacuation of 56,000 people in 48 hours. 4 hours after this evacuation was complete the volcano erupted with a pyroclastic flow and experienced its largest eruption for 1200 years.

Question 72

Focus

Answer 72

The point below the ground where the pressure is released and from where the seismic waves emanate in an earthquake. Can be shallow (0-7km), intermediate (7-30km) or deep (30+km).

Question 73

Epicentre

Answer 73

The point on the surface directly above the focus of the earthquake.

Question 74

Primary Waves

Answer 74

These are longitudinal waves. They are the fastest moving but the least damaging. They rock the earth backward and forward. Can travel through all strata of the earth.

Question 75

Secondary Waves

Answer 75

These are transverse in nature rocking the earth up and down. They bounce off the outer core as they cannot travel through liquids. These do a lot of damage but are slower to arrive than primary waves

Question 76

Suface Waves

Answer 76

There are two types here. Love waves snake left to right while Raleigh waves have a corkscrew motion. They exert omnidirectional stress on foundations and can cause collapse.

Question 77

Richter Scale

Answer 77

A logarithmic scale of earthquake energy.

Question 78

Mercalli Scale

Answer 78

Ranks earthquakes qualitatively from I (virtually imperceptible) to XII (complete destruction).

Question 79

Haiti Demographics

Answer 79

Population of 10 million people. 41% employed with 66% of those employed employed in the informal sector. The literacy rate is 53%. In urban areas, the sanitation rate is 24%. 50% of the population are below the UN poverty line. GDP $1240.

Question 80

The Earthquake - Haiti

Answer 80

On 12th January 2010 a 7.0 magnitude earthquake hit in the middle of the night. Its focus was 13km deep and 24km from the capital, Port Au Prince, where it caused 33% of houses to collapse. 200,000 were killed and 250,000 sustained serious injuries. 1 million people were made homeless.

Question 81

Haiti Earthquake - Initial Response

Answer 81

UN and WHO were in charge of the emergency response. Field hospitals were set up to treat the injured and food aid distributed. This caused civil disorder so UN troops were brought in. World Vision and Oxfam built tented refugee camps. Siting them was hard as only about 5% of land in Haiti was registered. Camps built at Corail (near airport) and Morassa (on a rubbish dump). Aid struggled to get in as there was only one runway. Some aid had to be brought in by land from the Dominican Republic.

Question 82

3 months on from the Haiti earthquake.

Answer 82

Bodies were still on the streets. No social security for the many injured and their informal businesses cannot run, causing the economy to collapse. A UN worker from Nepal introduces cholera to the country, this causes 600,000 cases and 10,000 deaths - costing the government $2bn to manage. The UN does not compensate them. The long term response starts.

Question 83

Long term response to Haiti earthquake.

Answer 83

Still NGO dependant. NGO’s give people microfinance loans to rebuild their businesses. They set about turning tented camps into proper settlements with tin roofs that will not cause as much damage if there is another earthquake than the concrete ones that were previously in use. The poverty rate has increased from 50% to 80% despite GDP rising slightly to $1240. These new houses are rent free but because a bus ticket to the city is the same as a day’s wages they are not that useful. There are crop trials and rice mills put in place in rural areas to help rebuilding efforts there.

Question 84

Haiti Now

Answer 84

Between 60 and 65,000 people still live in camps. Rates of sanitation have improved by 5-10%. Demographic is largely the same. NGO’s have been successful in terms of building resilience through earthquake drills but the country is still unsustainable with no emergency services. Earthquake caused $40bn of damage.

Question 85

Japan Tsunami

Answer 85

Occured on 11/3/11. A 9.1 magnitude earthquake 5 minutes in duration. Focus is 29k deep and 70km from the shore. 6km of water was pushed upward resulting in a wave of initially 1m. It hit NE Japan as a tsunami 20 minutes after the earthquake and then hit Sendai, closest to the epicentre, 35 mins afterward. In places the wave was 10m, rising to 40m in Myoko.

Question 86

How did defences hold up in Japan?

Answer 86

GDP PPP per capita in Japan is $46,000. As a result defences were good. Initial earthquake cause only cosmetic damage and some liquefaction in Tokyo. People headed the earthquake alert that gave them 1 min’s warning. There were 10m sea walls at places such as Sendai that should have protected them. These had subsided by 1-2m.

Question 87

Fukushima Daiichi Nuclear Power Plant

Answer 87

Automatically shut down after the quake with diesel generators kicking in to cool the reactor. The 5.6m sea wall, having subsided by 50cm, was overtopped by the wave and the plant was inundated with water. The diesel generators stopped and the plant went to battery power with the capacity for 8 hours. This was not in reality enough as 3 reactor cores melted down. People were evacuated from a 100km radius ensuring that there were no deaths among the public from radiation sickness. 100,000 people were evacuated. The World Nuclear Association has said that this overly cautious evacuation has led to 1000 needless deaths. Cost $180bn to cleanup, double the original estimate.

Question 88

Showing the strength of the Tsunami in Japan.

Answer 88

Water from the Tsunami carrying debris moved 7 miles inland. Cars were deposited atop 3 storey buildings.

Question 89

Overall impact of the Japan Earthquake and Tsunami

Answer 89

Total cost $325bn. 127,000 buildings destroyed, 750,000 seriously damaged. 500 aftershocks up to magnitude 7 were recorded in the following week. One at magnitude 7.1 was recorded in April. 20,000 killed. A 1m wave hit Hawaii, making this the first ocean crossing Tsunami in 40 years.

Question 90

Christchurch Earthquake

Answer 90

22/2/11. A 6.3 magnitude quake struck at 12:51. Mercali scale score of 9. Its epicentre was very close to (6 miles away from) Christchurch, the 2nd most populous city in NZ.

Question 91

Impacts of the Christchurch earthquake

Answer 91

185 people were killed with 2000 injured, 164 seriously. Its impacts on the CBD were estimated to have been worsened by the 7.1 magnitude earthquake on the 4th September 2010 having weakened foundations. Over half of the deaths occurred when the 6 storey Canterbury TV building collapsed. 80% of the sewerage system had been destroyed and 400,000 tonnes of silt had been moved in liquefaction. All schools were closed this afternoon because of a teacher’s union meeting.

Question 92

Immediate Responses to Christchurch Earthquake

Answer 92

A state of national emergency was announced, lasting until 30th April. There was a 5.9mag aftershock 2 hours after the original earthquake which hindered rescue efforts. 150 USAR personnel from NZ + 429 from overseas. The full crisis management infrastructure was in place within 2 hours of the earthquake. 300 reserve police officers were brought in from Australia. The number of officers in the city was boosted to 1200.

Question 93

Private sector response to the earthquake.

Answer 93

The majority of the response was coordinated by the government emergency committee, fire service and defence force. The Red Cross provided a humanitarian response. The energy company Orion restored power to 80% of the city by 5pm, within a week, water had been restored to 70% of the city. The water company brought in bottled water and portable toilets. The city was ensured against quake damage by Munich Re. They paid out, considering this a new event to the one in 2010.

Question 94

Long term response to Christchurch Earthquake

Answer 94

Despite the estimate that the rebuild could take 50-100 years and cost $40bn the CBD rebuild zone opened in June 2013. The 26 storey Grand Chancellor hotel had to be demolished having suffered 50cm of subsidence. 10,000 homes destroyed, 100,000 damaged.

Question 95

Boxing Day Tsunami 2004

Answer 95

Occurred at 6:59 local time. Occurred following a 9.0 magnitude earthquake between the Indo-Australian and Eurasian plates. $12.5bn damage done with 294,000 killed. It was the largest quake since 1900. A high speed train derailed in Sri Lanka, killing 600. Diarrhoeal diseases that followed the Tsunami killed many. 2 million jobs lost, 4 million fell into poverty. 1.7 million internally displaced. 410,000 homes destroyed and 500,000 injured.

Question 96

Formation of a Tsunami

Answer 96

Water is forced violently up when the plate being subducted under springs up. The shockwave sends multiple waves, incrementally smaller, out. Out at sea they are 1m tall. They have extremely strong currents. As the trough of the Tsunami wave approaches the shore its strong currents can pull water into the Tsunami wave, making it look like water is draining from the beaches. As it moves into shallower waters the eddy currents within the wave distort. This causes the wave to grow taller. As it slows down more water from under and behind can pile up into it. In some areas, there were 3 of these representing the concentric shockwaves while in some areas they slowed to such an extent (perhaps by reefs) that all 3 combined into one.

Question 97

Order of places being hit by the boxing day Tsunami.

Answer 97

Nicobar and the Andaman Islands as well as Banda Aceh province of Indonesia were hit immediately and devastated. Thailand was hit 30 minutes later. India and Sri Lanka were hit 1.5 hours later and the Maldives 3 hours after.

Question 98

Impacts of Boxing Day Tsunami on Local Areas

Answer 98

In Thailand, sea grass beds used in aquaculture and tourist areas were damaged.

Question 99

Reasons for the widespread damage.

Answer 99

Before 2002, 12% of Tsunamis reported were in the Pacific. These undeveloped countries could not afford to invest in a Tsunami warning system. Western agencies could have made their warnings clearer.

Question 100

International Response

Answer 100

By 1st January, £700m of emergency aid had been donated. In all $5.5bn of emergency aid had been pledged. US Pacific Tsunami Warning Centre created a new clearer warning system operating over three tiers. The third and most serious of these warns that a Tsunami is 1 hour away, states its expected magnitude and recommends the distance from shore that should be evacuated. A local tsunami warning centre was established in the Indian ocean. In Banda Aceh, Indonesia, 100,000 people were killed. The UN responded by building 21 water treatment plants, 200 schools and renovating 300 more.

Question 101

Difficulties in Earthquake Prediction

Answer 101

Their events release their energy with subsequent events releasing less unlike most natural disasters which build. Also, we can only make predictions when we know where faults are. This is a particular issue on the Eurasian plate, as seen when an earthquake occurred out of the blue in L’Aquila, Italy in 2009. Also, earthquakes develop several km down where it is difficult to determine conditions.

Question 102

Fault Laser/Manual Levelling

Answer 102

Determines movement along a fault, such as San Andreas. If the fault was to stop moving it would be a sign that energy was building.

Question 103

Seismometry

Answer 103

Can detect clustering of foreshocks and pinpoint epicentres so new faults can be discovered.

Question 104

Satellite Imagery

Answer 104

Can detect plate movement with respect to each other down to a few cm.

Question 105

Water table monitoring

Answer 105

Strain put on the earth in the run up to an earthquake can cause changes in the water table.

Question 106

Strain Gauges

Answer 106

Buried deep underground, as an earthquake builds up strain will increase.

Question 107

Radon Gas Sensors

Answer 107

As an earthquake builds, more Radon is released.

Question 108

Gravity, Magnet and Resistance Meters

Answer 108

Like strain gauges, these are buried and measure changes in rock properties at depth. Changes may indicate an imminent earthquake.

Question 109

Market Rasen Earthquake

Answer 109

27th February 2008. Strongest quake to hit the UK in 25 years. 5.2 on Richter scale. Only 1 man was injured when his chimney collapsed onto his bed. Falling bricks caused most of the £30 million damage. The focus was 18.6km deep with the biggest aftershock 2.2. This occurs at a transform fault from the mid-atlantic ridge.