RISK (R)= frequency or magnitude of hzard (H) X level of vulnerability (V) / capacity of population to cope and adapt (C)
Risk Management Follows...
1) ASSESS THE RISK
(store suppies, raise awareness,have emergency equipment, warning systems, insurance etc)
2) PRESCRIBE ACTION
(searh and rescue, medical centres, temporary accomodation, clean water, food, sanitary products, communication channels, turn off gas to prevent fires)
3) EDUCATED AND INFORM
(construct asesimic buildnigs, land use zoning, aid from gov to reconstruct, bilateral and multilateral aid, prediction and monitoring technology)
Process of Liquefraction:
1) Sediment shaken by seismic waves
2) Seismic waves amplify in soft unconsolidated soil sediments
3) Water saturdated sediments compact
4) Water forced upwards
5) Water and sediment erupt onto surface
6) Buildings subside into softer ground
PROPERTY DAMAGE, LOMA PRIETY 1989 (Marina District, 70 buildings suffered liquefraction)
Factors that Affect Hazard Perceptions
Past exerpeinces of hazards
Relgious view points
Dependency from others (family etc to look after)
Levels of perceptions affect responses
More affluent countries deal better with tectonic consequences, in societies where there are disparaties of wealth there may be condlict between different groups as safety levels vary
Evidence for Tectonic Plate Theory
Wegner (1912)- Theory of continents moving across earth. 300 million years ago the earth was 'pangea' which is why plates appear in a 'jigsaw shape'. Other evidence: same fossils, same rocks and glacial depositions
What drives tectonics?
Radioactive decay in the earth's 5000 degree core causes convection curents within the mantle. The magma in the mantle becomes less dense and rises in the astenosphere and becomes cooler as it reaches the crust and sinks again, forming a convecton current (and mantle plumes)
Conservative/ Transform Boundaries
Two neighbouring plates slide past each other, locking against each other. Results in a build up of tectonic pressure. When pressure is released, powerful earthquakes occur as movemet occurs along fault lines.
The San Andreas Fault, along west coast of North America where the Pacific and North American plates meet. Los Angeles and San Francisco at risk of tectonic activitiy.
Explain processes at constructive plate boundaries
At constructive boudaries two plates of the crust/ lithosphere are moving apart and diverging away from each other. Radioactive decay in the earth's 5000 degree core causes convection currents in the mantle which drives this process.
In the initial stages of formation a process called upwarping forces the crust upwards and begins to crack the crust due to pressure from the underlying convection currents in the mantle, creating a mantle plume.
As the crust becomes further stretched, fracturing of the plates forms new crustal material. Cracks in the crust create fault planes along either side of the plate boundary. Eventually, this fracturing will create a rift- such as Thingvellier in Iceland. Volcanoes are common along these fissures. The Icelandic volcano Kraftla is situated on a hot spot and last erupted in 1984, along a 14m fissure. The Great Rift Valley formed by the African and Arabian plates is another example.
As the divergence of plates continues, injection of magma and volcanic activity create new thin oceanic crust within the rift valley. As the rift valley drops below sea level, a lines sea is created- like the Red Sea. Eventually the processes above lead to the formation of new oceans, through sea floor spreading. For example, the Mid-Atlantic Ridge is formed by the Eurasian and North American plates moving apart at a rate of 2cm per year (diagrams)
An earthquake is a release of energy resulting from the build up of stresses within the earth's crut. 85% of earthquakes occur along plate boundaries.
When an earthquake occurs, seismic waves are recorded on seismographs. Primary and secondary (slower) waves are compared to deterimine earthquake locations. The point of fracture in the crust is the focus or hypocentre The point on the Earth's surface directly above is the epicentre.
Explain processes at destructive plate boundaries
1) plates diverge at lithosphere, driven by convection currents in mantle, caused by radioactive decay in 5000 degree core.
2)Oceanic/ continental- less dense oceanic is subducted, creates subduction zone and ocean trench (peru- chile trench off coast of South America with Nazca subducted beneath S. American 3)Oceanic can stick whilst being subducted at Benioff Zone, powerful earthquakes (1960 May Chile earthquake, 9.5 Ritcher Scale) DIAGRAM
4) Heat is generated at subduction zone due to friction and oressure, causes partial melting of overriding plate, forming magma (melted crustal material, sediment, water). Less dense magma than surrouding crust is buoyant and rises upwards- violent volcanoes (Puyehue Chile volcano 2011). Rising magma can cool and block vents causing more tectonic activity
5) Oceanic/Oceanic- Denser oceanic is subducted, Island Arcs (Philippines Island, Philippine and Eurasian Plates)
6)Continental/ Continental- younger rock folds due to compressional forces. Neither is subducted (no volcanic activity). Fold Mountains (Alps- African + Eurasian), Himalayas (Indian + Eurasian)
Process of Tsunamis:
1) Earthquake seismic waves cause large waves (trigger point)
2) In deep water, tsunami moves at fast speeds (fast, small waves)
3) As tsunmai reaches shallow water friction slows it down but increases in height (up to 3m)
4) Tsunami's don't have crusts (keep increasing)
5) Can spread over 1km in land and rise up to 30ft
26TH DECEMBER 2004, Kalutara Sri Lanka- no warning of approaching tsunami- water reached at least 1km in land causing mass destruction
A quater million people died as a result of the 2004 Boxing Day Tsunami
Briefly describe groundshaking
Buildings collapse, killing people
Port- Au- Prince, Haiti - 12th Jan 2010
Briefly describe landslides
Earthquakes trigger slopes to fail
1995- Kobe, Japan
How to measure magnitudes of earthquakes
Ritcher Scale (earthquakes energy released): 1-10 from shaking to total destruction
(an earthquake scoring '3' is 10X stronger than a '2')
(e.g- Dudley earthquake compared to Port-Au-Prince)
Mercalli Scale (affects of earquake): 1-12
'detected by sensitive instruments right to total destruction
Factors Affecting Earthquake Impacts
- ECONOMIC DEVELOPMENT- better infrastructure etc
-URBAN OR RURAL AREA- urban means more collapses
-DISTANCE FROM EPICENTRE- closer is more intense
-TIME/DAY OF WEEK- more people about in risk areas
-WEATHER/SEASONS- frost bite, wind etc
-EMERGENCY RESPONSE- more prepared
-LANDSCAPE/ROCKS- harder rock won't liquefy/ slide
Japan National Disaster Prevention Day
1st September (anniversary of 1923 Great Kanto Earthquake)
Emergency services engaged in event, with institutions such as schools also taking part
Hazard skills taught; how to prepare emergency kits, where the safest places are, where emergency meet up points are located, role planning disaster scenarios to be prepared
Over 2 million took part in 2014
Earthquakes can be managed by...
Predict inensity and location, but not timing. Able to then use land use planning to avoid building important infrastructure in 'high risk zones'
90% of 60,000 killed in last 10 years by earthqaukes was due to building collapse
vital factor within preparation and during aftermath- affects recovery rate of an area etc
Taipei 101, Taiwan (Tuned Mass Damper System)
- Withstands typhoon winds, earthquake termors (from Asia Pacific)
- Steel pendulum weighing 660 tonnes, suspended from top
- Concrete blocks mounted to sky scraper to counteract oscillations
- Open areas
- Automatic window shutters
- Reinforced lift
- Concrete walls
- 'Bird cage' interlocking steel frame
Land Use Planning...
Land use planning is used to identify the most hazardous areas concerning tectonic activity, then important buildings such as hospitals can be built in 'low-risk' areas.
Sufficient open spaces are needed between places and buildings to escape
Kobe, Japan- hose pipes, walls to separate areas and greenspaces to minimise impacts
California Shake Out...
OCTOBER 21ST (began in 2008)
6-9 million participated in 2010
'Drop,Cover and Hold On' event
'Great Shake out Eathquake Drills'
Events which families, individuals and large groups can all participate in +Videos created to help recap on skills taught
Advice such as; anchor possessions onto walls, have emergency kits and escape routes planned, try not to shout if trapped due to dangerous partcles in air etc.
MEDCs have; health, police, fire provisions whilst LEDCs deal with the aftermath rather than prevention.
MONTSTERRAT (VOLCANIC ERUPTIONS)
First erupted July 1995, largest June 25th 1997
Killed 19 people
7 to 50% unemployment rate after volcanic activity
Britain offered £2,400 to each adult in 1997 as aid
900m eruption cloud with pyroclastic flows, gas emission made air unsafe
Loma Prieta, California 1989
17th October 1989
epicentre- 50 m from San Francisco and 6.9 R.S
63 deaths and 3,800 injured
13,000 homes damaged
$6bn economic damage
Collapse of Cypress Express struture, section of interstate 880 Oakland, collapsed killing 42 people. Took 9 years and $1.2bn dollars to rebuild
2 miles of San Francisco bay bridge collapsed, closing for 2 months
Marina District suggered liquefraction and 70 structures were damaged
Restoration of gas line cost $20 million
Future Hazard- California
99% probability of quake in next 30 years where;
- 1,800 would die
- water systems destroyed
- buildings not ready for another earthquake
California is using terrashake and cybershake technology to predict location and intensity of earthquakes, however when cannot be predicted.
Haiti, Port- Au- Prince 2010
12TH JANUARY 2010
Conservative movement along Caribbean tectonic plate and North American plate
Over 250,000 deaths
300,000 injured and 1.3m homeless
economic impact equitable to 120% of GDP
Cholera- with 9000 oficially needing treatment
Soft sediment amplifies waves, increasing impact
Building design, land use and community preparedness all contribute to disaster
Landslides, tsunamis, port destroyed, shanty towns = AFTERMATH
Located on constructive plate boundary (Eurasian and North American plates)
Spanning the Mid-Atlantic Ridge, Iceland emerged as a result of the divergent, spreading, boundary between these two plates and the activity of Iceland´s own hotspot or mantle plume.
TOURISM- geological attraction, stand on mid-ocean ridge, geyser steam pool, blue lagoon, geothermal spas
GEOTHERMAL ENERGY- Once reliant on peat and oil imports but now can directly provide 89% of heat to icelandic homes. Heat for pools, cooking, greenhouse- producing 4,600 GH of electricity.
NESJAVELLIR plantation- North east side of Hengal Mountain, supplies 1,100 L/sec of 82-85 degree hot water through 27km pipline to Rekjavik- most powerful geothermal well in world.
Less affluent countries often cannot afford asesmic designs such as Taipei 101, instead they have to take individual percautions and preventions when building, such as;
- Heavy roof replaced with lighter building material
- Straw building materials
- Sock absorbers