lecture 1 - Myweb @ CW Post

(lecture on 9/8/08)
Introduction: Hazards and Risk, Energy Sources for Natural Disasters
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Natural Disasters and Humans, Hazards and Risk (Chapter 1 and supplemental)
Energy Sources for Natural Disasters (Chapter 2 and supplemental)
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Natural Disasters and Humans, Hazards and Risk
objective: to study the natural Earth processes tat pose hazards to humans and
methods of reducing risks from these natural hazards.
key points: we must study
1) physical processes in the dynamic Earth system
especially those associated with unusual or extreme events
2) effects on people, property and infrastructure
3) methods of monitoring so as to try to predict extreme events
4) methods to mitigate the effects of extreme effects
Extreme events are not disasters. Natural processes and the occasional extreme
events are not disasters. They are just ongoing natural processes. But they do pose
natural hazards for humans, depending on how well suited our property/infrastructure/
habits are to these natural processes.
Extreme events simply refer to the largest of the naturally occurring events. Large
magnitude events occur relatively rarely compared to the average event for Earth
processes.
Natural disasters occur where humans and natural processes, particularly extreme
events, collide with human activity.
The 40 deadliest disasters, 1970-2005 include hurricanes, earthquakes, tsunamis,
heatwaves, floods, volcanic mudflows, and snowstorms.
Between 1947 and 1980, the largest number of people died in hurricanes followed
closely by earthquakes.
The monetary cost of natural disasters has grown more than tenfold through the last
half-century as global population has approximately doubled, and development has
also greatly increased. Population is still growing fastest in developing nations,
those who are least able to prepare for and cope with the aftermath of natural
disasters. The global cost of natural disasters in 2004 was over 73 billion dollars
(equivalent to about 3.5% of the U.S. federal budget for that year). Natural disasters
cost ~73 billion dollars per year in the U.S.

Developed countries overall experience much higher monetary losses and low human
losses. Developing countries have high casualties and more modest monetary
losses due to less development.
Definitions
Hazard (H) refers to the possibility of a dangerous event. Hazard can be expressed as
a statistical probability of a given magnitude event occurring in a specific area within
a specified length of time.
Vulnerability (V): the level of loss expected from an extreme event (of a given
magnitude). It can be quantified from 0 (no loss) to 1 (total loss).
Specific Risk (Rs): the probability of a loss. Quantitatively, is is the product of Hazard
and Vulnerability (Rs = H x V).
Net Impact: the difference between disaster losses and the benefits of using the
hazardous area.
Medical Consequences
Mortality: number of deaths
Morbidity: number of injured
Traumas: numbers of burns, contusions, fractures, lesions, etc.
morbidity > mortality in earthquakes and hurricanes
mortality > morbidity in landslides, floods, volcanic eruptions
Types of Disasters
geophysical origin: earthquakes, tsunamis, volcanic eruptions, landslides, etc.
climatic origin: hurricanes tornadoes, severe thunderstorms, floods, drought, fire, etc.
biological origin: epidemics, parasite invasions, etc.
human origin: warfare, terrorism, urban fires, building collapse, etc.
Recurrence Intervals
Low or moderate magnitude events generally occur frequently while large magnitude, or
extreme events generally occur rarely.
The Disaster Cycle
Impact - Response - Recovery - Mitigation - Preparation - Next Impact

Energy Sources of Natural Disasters
(see the extensive notes in the lecture slides online)
The sources of energy for natural disasters are:
- internal heat that drives geophysical processes like the motions of plates,
earthquakes, and volcanoes
- solar radiation which drives the water cycle, weather and storms
- gravity which causes landslides and tidal processes
- impacts by extraterrestrial bodies
Origin of the Earth - Origin of Earth’s Primordial Heat
solar nebula hypothesis
heat in early Earth derived from
- gravitational compression
- impacts
- radioactive decay (greater than today)
differentiation of Earth’s core, mantle, crust, hydrosphere, and atmosphere
Earth’s Internal Heat Engine
- interior is hot today because of primordial heat and continuing radioactive decay
- mantle convection
Energy from Outside the Earth
- solar energy accounts for 99.98% of the energy at the Earth’s surface
- the water cycle is driven by solar radiation
- the rock cycle is driven partly by internal heat, partly by solar radiation (and gravity)
Constructive and Destructive Forces
- internal energy drives mountain building, volcanoes, etc. which build up the land
- solar energy drives the water cycle responsible for weathering and erosion of land
Energy Sources of Extreme Events
- energy accumulates gradually over time
- when energy is suddenly released, extreme events occur
- the human built environment is designed mainly for the gradual flux of energy but may
be damaged or destroyed by sudden energy release (extreme events)
Internal Heat Energy
- earthquakes
- tsunami
- volcanoes
Solar Radiation
- severe weather
- tornadoes
- tropical cyclones (hurricanes, typhoons, cyclones)
- floods
- drought, fires

Gravitational Energy
- landslides & avalanches
- erosion
- tides
Impact Energy
Tiny impacts occur constantly. Large impacts occur rarely, but when they do:
- impact craters
- shock wave
- earthquake and tsunami
- molten ejecta
- thermal transient
- fires
- sudden, short term cooling
- extinctions