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Presentation: “Natural Hazards” Prepared by Oleksandra Pekhn’o Form 11-A School of Chynadiievo
Introduction to Natural Hazards What is a “Geohazard”? Earth processes (involving the lithosphere, hydrosphere & atmosphere) that, upon interaction with human activity, cause loss of life and property It is important to understand the human element without it, there would be no hazard because of it, the science of geohazards becomes more important every year mitigation: reduction/prevention geo- process human process Hazardous condition or result
The Earth’s population is increasing more people living in hazard-prone areas populations are becoming hyper-concentrated consumption of resources examples: today there are 6 billion people on Earth ( ~ 50% live in cities) by 2025, there will be ~8 billion people (~ 66% in cities) of these cities, 40% are coastal prone to severe storm and tsunami damage and a large majority lie in areas subject to other geohazards (for example volcanoes and earthquakes) Why is the human element so critical?
CANNOT stop the geologic processes CANNOT stop the population growth/expansion Therefore, we must try to reduce (mitigate) the hazards through: scientific study population education changes in engineering/building practices management plans and hazard response scenarios
Earthquake Hazards These are important hazards to understand: the natural hazard that on average kills the highest number of people per year (> 1 million during the past century) commonly strikes without warning no time for evacuation not a predictable trend to earthquake numbers, magnitude or location 1000's of large earthquakes every year ~ 20 are > M7.0 and these account for 90% of the energy released and 80% of all the fatalities
How do we mitigate the hazard from earthquakes? Reinforce buildings Education Disaster plan
Earthquakes and Tsunami’s An earthquake under the ocean has the potential to form a tsunami. The earthquake must vertically displace overlying water (extensional or compressional faults - not transform) Extension Compression Transform
2004 South Asian Boxing Day event Biggest earthquake in 40 years! Magnitude 9.2 150 km off the west of Northern Sumatra Generated a disastrous tsunami in 12 countries
The earthquake occurred at a convergent tectonic plate boundary (subduction zone) An estimated 1,600 km (994 miles) of faultline slipped about 15 m (50 ft)! The earthquake released 20 x 1017 Joules of energy Equivalent to: 475,000,000 kg of TNT 23,000 Hiroshima atomic bombs! Second largest recorded earthquake
How do we mitigate the hazard from tsunamis? Monitoring process is very technology-intensive high costs for many poorer countries often no technology available to monitor local tsunamis for example, Papua New Guinea has no monitoring stations reliant on the Pacific Tsunami Warning Center tsunami in 1998 was not detected
Seawall construction cause early wave breaking prevent wave run up into urban areas How do we mitigate the hazard from tsunamis?
Education warning systems evacuation plans general understanding of the hazards involved Punishment From God 45% Natural event 35% Bomb 20% Population reaction: Papua New Guinea (1998) How do we mitigate the hazard from tsunamis?
Most widespread destructive weather hazard For example: Hurricane Floyd (1999) only a moderate level hurricane caused US$5.6 billion in damage in the Bahamas and North Carolina (USA) and 57 fatalities Tropical Cyclones (Left) Three different cyclones spinning over the western Pacific Ocean on August 7, 2006.
How do cyclones form? The above figure shows how cyclones form. The green arrows show where warm air is rising. The red arrows indicate where cool air is sinking.
Cyclone Categories The Saffir-Simpson Hurricane Scale Category Wind Speed (mph) Damage at Landfall Storm Surge (feet) 1 74-95 Minimal 4-5 2 96-110 Moderate 6-8 3 111-130 Extensive 9-12 4 131-155 Extreme 13-18 5 > 155 Catastrophic 19+
Hurricane Katrina Hurricane Katrina was the most costly and most deadly hurricane in the history of the USA. Category 5 At least 1,836 fatalities Damage estimated at US$ 81.2 billion
What damage is produced? Storm Surge water that is pushed toward the shore by the force of the cyclone winds.
What damage is produced? Wind responsible for the loss of power and utilities wind damage affects larger areas than surge flying debris tree loss
How do we mitigate the hazard from a cyclone? Monitoring early warning systems Infrastructure cyclone walls communal shelters Education and planning
Natural Hazards Summary Graph showing the number of deaths per year due to natural hazard events