Natural Disasters - Download as PowerPoint - PowerPoint by yx0ASuy



John Gyakum (AOS)

John Stix (EPS)
  What are we talking about ?


dis - unfavourable

astro - stars

To the ancients,
 disasters were
 precipitated by the
       Our role as scientists

In a sense, the
 essence of science is
 to be able to
 PREDICT natural
  phenomena, to
  REDUCE     their
Katrina, Monday 29 August 2005, 0715 hours Zulu time
Courtesy Washington Post
Courtesy Washington Post
Katrina reaches
        Some destructive
        natural events

Earthquakes: local to regional
Floods: local to regional
Hurricanes: regional
Tsunamis: regional to global
Meteorite impacts: regional to global
        Relative energies of
        selected phenomena

 energies and
 magnitudes for
 phenomena (from
 Brumbaugh, 1999)
  Some important definitions

Hazard: potential threat to humans and
 their welfare

Risk: probability of loss (deaths, injuries,
 damage, disruption of economic activity)
 as a result of a particular natural event

Vulnerability: potential loss, or degree
 of loss, from the event (e.g., 0=no
 damage, 1=total loss)
       Definitions (ctd.)

Disaster: a hazardous event affecting a
 community in an adverse way such that
 essential social structures and functions
 are disrupted
         Definitions (ctd.)

Prediction and forecasting: statement
 that a particular natural hazard will occur
 with a given probability during a certain
 time frame in a specified geographic area

Mitigation: efforts to reduce or minimize
 the effects of natural hazards on a
                               Risk of death1

 Volcanic eruption:                            1 in 30,0002
 Asteroid impact:                              1 in 20,0002

 Earthquake:                                   1   in   200,0003
 Lightning:                                    1   in   130,0003
 Tornado:                                      1   in   50,0003
 Hurricane:                                    1   in   25,0003
 Airplane crash:                               1   in   20,0003
 Auto accident:                                1   in   1003

   1to   an individual over a 50-year period
   2worldwide

   3USA    only
   A question for all of us

Why do people
 live where they
 do ?
    People’s reactions to
    crises and disasters
Anger at scientists, officials, etc.
Frustration, especially if event is long-
Skepticism, which can be fostered by
 the media
Suspicion…a “plot”
Refusal to evacuate; people feel safest
 in their familiar surroundings
     Prediction of natural
Where are we ?
Long-lived vs. short-lived events
Predictable (hurricanes) vs.
 unpredictable (earthquakes) events
Problem of human time vs. geologic
Probabilities of scientists vs. exact
 date and time of ordinary people
   Scientific understanding of
   natural phenomena

Occam’s Razor: when several conflicting
 hypotheses or explanations are proposed
 for the same set of observations, the best
 explanation is that with the fewest
 independent assumptions
         Causes and effects

A cause-and-effect relationship - and
 associated predictions - is an inherently
 deterministic view

It works only with events whose
 outcomes occur with nearly 100%
 probability, e.g., flooding as a result of
 tidal forces

Mother Nature is non-deterministic

Individual events are inherently

This requires a statistical approach
 such as probabilities, since we don’t fully
 understand many natural processes
  Recurrence intervals and

Recurrence interval: average time
 interval between the occurrence of two
 events of given magnitude

An example is a flood of 6 meters which
 happens once every 50 years, on average

Or an earthquake of magnitude 5 which
 happens once every 10 years, on average
    Recurrence intervals
    and probabilities

The flood: there is     The earthquake:
 a 1 in 50 chance that    there is a 1 in 10
 such a flood will occur  chance that such a
 in any one year…         quake will occur in any
                          one year…
this corresponds to a
 2% probability of       and thus a
 occurrence               10% probability of
An example of non-determinism

 A flooded city from a
  swollen river…

 …is the flood the
  source of devastation,
  or the dikes built to
  modify the course of
  the river?
   Another example of non-

Casualties and
 destruction from a
 volcanic debris flow…

…did the flow cause
 the disaster, or the
 siting of the town on
 debris flow deposits
 of older eruptions ?
   The Cretaceous-Tertiary
   (K-T) extinction at 65 Ma

End of the dinosaurs and other species

In fact, about two-thirds of all species wiped

80% of all individuals killed off

Thereafter, mammals took over

The Great Wave off the Coast of Kanagawa, by Hokusai, a famous late
       eighteenth- and early nineteenth-century Japanese artist.
   4 case histories

Alaska 1964 (earthquake-generated)

Krakatau 1883 (caldera-generated)

Unzen 1792 (landslide-generated)

Grand Banks 1929 (submarine landslide-
   Volcanoes and volcanism

 Volcanoes represent
  venting of the Earth’s

 Molten magma rises
  within the Earth and is
  erupted either quietly
  (lavas) or violently

                            Sakurajima Volcano, Japan
                            Cinders were issued up to >2,500 m high
                            18 May 1991
 Volcanic activity: pyroclastic
 Pyroclastic flows are
  suspensions of hot
  pyroclastic material, air,
  and gas which descend
  under the influence of

 Their velocity is generally
  very high (50-500 km/hr)

 This example is a flow
  from Mt. St. Helens
Avalanches were first imagined as
giant snowballs which increased in
size from accretion of underlying snow
powder avalanche
due to cascading
down near-vertical
Hurricanes (continued)
New Orleans; August 2005
El Niño
Ice Storms
            Web sites and readings

 Definition of terms used in this course:

   Useful general web sites:
 (clearinghouse of disaster-related information)
 (links to useful disaster-related sites)
 (current events)
 (topics on disasters) (Natural hazard map of Canada)
 (an interactive tool to make hazard maps for the
 (interactive hazard maps of the Pacific Ocean basin)
 (information on
    various natural hazards)
 (images of various natural phenomena)
 (images of various natural phenomena)

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