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Tectonic Processes and Hazards, Why do the effects of Earthquakes Differ ?…
Tectonic Processes and Hazards
Hazards ?
Why are some, locations at more risk tectonic hazards?
Hazard
<A potential threat to human life and property.A natural hazard can either by hydro-meteorological(caused b climate processes)or natural geophysical (caused by land processes)
Earthqauke,Volcano and Plate Tectonic
Geophysical hazards occur near a plate boundary
, these plates move at different speeds and directions which can cause Collison, earthquakes volcanoes.
Earthquakes can also occur near middle of plate boundaries called
intra plates
. The cause of this is not fully known yet tis thought we have pre existing weaknesses which become reactivated, forming seismic waves.E.g solid crust cracks over millions of years of weakening and builds up so much pressure it causes an earthquake.
Volcanic Hotspots
, such as the ring of fire, in the pacific, are also situated in the centre of the plates. This is the localised area of the lithosphere(earths upper crust and mantle)which has an unusually high temperature, due to upwelling of hot molten material from the core, The magma rises from a plume and forms land masses such as
Hawaii
.
Plate and Tectonic Theories(Studies and Evidence)
Earth Structure
Crust
-400 Degrees C(solid)
Mantle
-870 Degrees C(phases of liquid/solid layers)
Outer Core
-4400-6100 Degrees C(Liquid/generates magnetic field)
Inner Core
- 7000 Degrees C(Solid + radiates heat + huge crystals)
Types of Plate Boundaries
Destructive(also called convergent)
are consistent of an oceanic plate subducting continental plate boundary. They are very dangerous and violent(both earthquakes and volcanos)e.g. Nazca to South American plate meeting.
Constructive
are a type of plate boundary where the two plates pull away from one another; they too are very violent (both earthquakes and volcanos)e.g. Nazca to Pacific Plates. There is also less friction along constructive boundaries so typically the magnitude of an earthquake is lower.(less stressful)
Transform
are a type of plate where the two rub together. They are violent in terms of earthquakes yet not volcanos .E.g. Pacific plate(oceanic) and North American(continental) creating things such as the San Andreas fault line along the West coast of Northern America
Collision
are consistent of two plates directly hitting one another. They are violent in earthquake nature and not volcanic nature. An example of this is The Indian(continental) subsiding the Eurasion(continental) plate.
**Other Evidence of tectonic theory
Another clear evident shows was how seismic waves travel through the Earth. Along the
Wadati-Benioff foci/zone
, the depth of waves shows subduction of the denser basilic oceanic plates into the upper mantle(shows the subduction of plates).
Wegener's Continental Drift theory
-States that then shape of south America and Africa seem to fit together so were once part of a supercontinent. As the plates moved, the continents separated, this was further verified as similar fossils could be found were these plates could have lined up, but are now separated by ocean.
Sea Floor Spreading
, occurs when the two oceanic plates move away from one another. Allowing magma to rise from the mantle and form new crusts ridges within the ocean, resulting in sea floor widening.
Hazards,Disatser and Vulnerability
General Info
In
2000
over
700 million were effected
by
170 disasters.
UN Definitions
Disaster = Defines a Disaster as
more then 500 deaths
**
A
"Mega Disaster"**
= is categorized as when either
2000 or more deaths
occur,
200,000 made homeless
,
dependence on aid for more then a year
or if the
GDP
of the country effected is
reduced
significantly (usually by
more than 5%
)
Vulnerability
= How suceptible a population is to dmaage caused by a hazard.
Resilience
how well a population can cope with said hazard.
Why do people stay exposed ?
lack of Alternatives
,Hard to tell people to pack up and leave their home so people refuse, and simply stay.
Changing Levels of Risk
-Deforested areas become more exposed to flooding.
unpredictability
, of the event (may be hard to predict and therefor people run the risk).
Russian Roulette
-People are conflicted with statistics and religious people take the risk as its all "gods plan".
Cost vs Benefit
-An example would how farmers sue volcanic soil, at the base of a volcano, for its fertile soil. So they run the risk of volcanic hazards but for the benefit of more profitable and efficient crop yields.
Risk
=
Hazard
x
Vulnerability
/ Capacity to cope(
resilience
)
Degg's Model
-suggests a disaster only happens when a hazardous event ,meets a vulnerable population. It indicates that the more vulnerable the population, the higher the risk for disaster.
PAR Model(Pressure and release Model)-
Proposes
what should be tackled
if the
risk of a disaster is to be reduced.
Vulnerability greatly influences the PAR Model. There are
5 Types of vulnerability
it looks into.
Environmental Vulnerability
-Location is at an higher risk than others due to population pressures.
Social Vulnerability
-A household or community are unable to support the disadvantaged within, leaving them at risk of hazards.
Economic Vulnerability
-People risk losing jobs, assets and money.
Knowledge Vulnerability
-People lack education, training or warning of a hazard.
Physical Vulnerability
-Living in a hazard prone area, with buildings offering little protection.
Types of Earthquake Waves
Primary Wave
-arrives first, fast moving, pass through solid rock/fluid. Pushes and pulls ground and gives it a "wobble" effect
Secondary Wave
-Slower moving than P wave, only moves through solid rock in an up and down movement.
Rayleigh Wave
-Only tends travel through the surface of the curst and in a rolling motion. Ground is moved up and down/side to side. Felt by people.
Love Wave
-Only travels through the surface of the crust, fastest of the waves and moves from side to side(horizontal) as it moves forward.
Geophysical Primary Hazards
Tsunamis
-produce by sub-marine earthquakes at subduction zones. Causing water displacement and deep trough waves. Also causes coastal erosion ,which is Malibu/Santa Monica in California.
Volcanic Hazards
Type of volcano
Shield Volcano
-More flat and longer base yet less dangerous and violent/more of a trickling flow of lava.10 degree or lower.
Composite Cone
= More dangerous
Hazards causes by the physical Volcano
Gases Produced
-E.g.Pinatubo,Phillipines,1991 produced a 20 million tonne sulphur dioxide cloud which rose to 32km high and cooled the earth for 3 years by 0.6 degrees. When combined with rain it can cause "acid rain".
Lahars
-After pyroclastic flow melts snow it can travel very fast with unstoppable force. E.g. Armero,Colombia in 1985,it spread 100km in 2.5hours and killed 23,000 people: most of which were asleep as this occurred at 11.35pm.
Ash Cloud/Tephra
-E.g. Eyjafjallajökull(EFJ),2010,Iceland,ash clouds prevented any trans Atlantic travel for a full week.
Laval Flow
-Basaltic lava flow is less Viscous and flow faster, people can escape, however anything gin its way will be burnt and destroyed. Composite volcanos have more viscous and slow moving lava. Lava bomb can be hazardous to people. E.g. Nyiragonga in 1977 400 people were killed in their sleep as a fissure caused a lava lake to drain in less then an hour from the crater.
Jokulhlaup
-Major cracks in the road /breaches which allow water and deposits to pass through and potentially causing damage. E.g. occurred in Eyjafjallajökull(EFJ),2010,Iceland but had no drastic effect.
Pyroclastic flow
-fast hot mix of substance. E.g. Chances Peak,Montserrat,1957,destroyed capital city Plymouth.
Management and Mitigation of Tectonic Hazards
Richter Scale
-Measures seismographic data of high frequency and indicates an intensity.
Higher magnitude = less frequent occurrence
Mercalli Scale
-Measure of observation(how much damage has been generated)useless if the earthquake event was in a dessert.
Moment Magnitude Scale
-Relates to the amount of movement of rock and the area of the fault or fracture surface.calculted values can be easily compared to magnitude values for other events. It practically measures the amount of energy released in the earthquake rather then the size of the seismic wave.
Park Model
A Graphical representation
of
step carried out in hazards recovery with a rough indication of time frame.
Can be used to compare hazard events. Steepness of the curve shows how quickly an area deteriorates and recovers. The depth of the curve shows the scale of the disaster(E.g. Lower the curve, lower the quality of life)
Stage 2 - Rehabilitation(Days-Weeks)
-Services begin to be restored/Temporary shelters and hospitals are set up/food and water distribution/Coordinated Foreign aid.
Stage 3 - Reconstruction(Weeks-Years)
-Restoring the area to the same quality of life if not better/Area is back to normal/Infrastructure rebuilt/Mitigation efforts for future events.
Stage 1-Relief(hours-days)
-Immediate local respone/foreign aid.
Hazard Management cycle
The
HMC
is
stages of responding to events
, showing how the same stages take place after the event.
Recovery
-Long term responses(restoring services, reconstruction)
Mitigation
-Strategies to lessen the effects of another hazard(barriers, warning signs, observatories).
Response
-Immediate action taken after the event(evacuation, medical, rescue)
Preparedness
-Being ready for the event to occur(public awareness)
Mitigation and Adaption
Can
reduce the loss
by
modifying the event
(changing who is affected by the hazard or tying to stop any secondary hazards occurring) or by
modifying the resilience or vulnerability
of the people likely to be affected.
Strategies to modify the Vulnerability and Resilience
Education
(teaching the community how to get the best chance at survval)
Hi Tech Monitoring
(can capture any anomalies/prior to a potential event).
Community preparedness
(E.g. fake earthquake drill alarms)
Strategies to Modify the event
Hazard resistant Buildings
(E.g. aseismic skyscrapers).
Engineering defences
(E.g. sea Walls to minimize tsunami effect)
Diversion of lava flow
(E.g. Italy divert flow of Mount Etna in 1983
land use zoning
(selecting what goes where so less areas of risk are sued up).
Strategies to Modify the loss
Emergency Aid
-This can be long term or short term but can make a country dependant.
Insurance
- Some mat rely on insurance to recover losses.
World Risk Index
Susceptibility
Coping Capacity(resilience)
Exposure
Adaptive capacity
Multiple Hazard Zones
Areas with in multiple occurring hazards within one potential time scale.
Risk Disk
- Decline in disaster deaths in terms of preparedness, mitigation(reducing severity) response, and recovery,
Earthquake related Case Studies
2010 Haiti Earthquake
Location - 25km from Capital Port-au-Prince./Date of event = 12 January 2010/magnitude of 7.3 and lasted around one minute./Plate involved = Caribbean plate and North American Pate(transform)
Environmental Impact
- Factories destroyed on the outskirts of the capital polluted the surrounding environment and was found in waster systems which lead to wildlife and human health concerns.
Economic Impact
- Losses were valued at around 3.6 billion USD which at the time was around 120% of its total annual GDP.
Social impact
- 1.3 million made homeless/ 250,000 killed sand 300,000 injured/
2011 Tohoku Tsunami
Location- Japan(Northern Region)/Date of event = March 11th 2011(magnitude 9-9.1)/Plate involved = Subduction plate boundary between the Pacific(subduction) and Eurasian plate(destructive)
Social Impact
- 15,899 deaths/6167 injured/450,000 displaced
Environmental Impact
- Farmland/ecosystems were completely destroyed.20Km exclusion zone as of nuclear meltdown in Fukushima Plant.
Economic Impact
- Severe infrastructure damage was done.Halted all production in northern Japan for many days/weeks.
2018 Lombok
Location - Indonesia/Population - 218,533/Date of event = 5th august 2018(Magnitude 6.9)/Plate involved = Australian plate moving under the Sunda Plate(Indonesian)
Environmental Impact
- Lifted the island almost 25 centimetres in some areas. In other areas the ground dropped 15cm
Economic Impact
- 80% of the region was damaged = $342 million in damages)
Social Impact
- Dead = 563 and Injured = 1,300
Volcano related Case Studies
Composite Volcano
Mount Merapi
(island of Java/Indonesia)/"Mountain of Fire"/9551 ft tall/Australian and Eurasian plate movement caused an eruption on October 26th 2010.
Economic Impact
- Ash deposited with rain creating a lahar and destroying many parts to the local eco system
Environmental Impact
- Prices increased on veg as of crop damage being so serious. Damage to ski cliffs and causes million of dollars of debt.
Social Impact
- 200,000 homeless/353 killed
Shield Volcano
Mauna Kea and Mauna Loa
(located - Hawaii)9Km above sea level and experiencing eruptions from 1983 to 2018 of very short and less violent scale.
Multiple Hazard Zone Case Studies
Bangladesh
Why a MHZ ?
2.
Geology
- Situated on a delta meeting, so seasonal floods are worse.
1.
Geology
- Very low lying(two thirds less then 15 feet above sea level)
3.
Plate Boundaries
- Placed on Eurasian/Indian and Burma Plate and therefore very prone to tectonic activity of all kinds.
Philippines
Why a MHZ ?
2.
Situated on the pacific ring of fire
- Very prone to tectonic activity hence the "fire".
3.
High Typhoon rate
- averages 20 a year.
1.
Low doctor to patient ratio
- There are more people then people to care for them.
Plates Boundary
-Placed on a collision plate boundary so its susceptible to earthquakes.
Why do the effects of Earthquakes Differ ?
Underdeveloped Countries
-Struggle more socially. They typically can't afford their own aid/regeneration.
Developed Countries
-struggle more Economically and yet have more in place to protect society.
Physical Location
-E.g. Land locked countries typically aren't effected by tsunami un less very low lying, compared to coastal countries.
Population
-Typically more people = More people to be harmed.
Types of Plate Boundaries.
Its Causes
Tsunami
-As energy(built from the earthquakes epicentre)approaches a shoreline the base of the wave slows down, shortening the wavelength and allowing for them to build in height(sometimes growing x20 the normal wave height).
Shockwaves
Liquefaction
-Spade in the soil increases and become s like a liquid .E.g. San Francisco in the 1980's earthquake struck and houses sunk into the ground, as of liquefaction.
Avalanches
Landslides