Prediction of Natural Disasters

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Prediction of Natural Disasters

• Art Lerner-Lam
• Associate Director
• Doherty Senior Research Scientist
• Adjunct Professor
• Lamont-Doherty Earth Observatory of Columbia
  University

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Prediction of Natural Disasters

• What is a Natural Hazard/Natural Disaster?
• What is the difference between hazard and
  risk?
• Are natural hazards predictable?
• What constitutes a prediction?
• What role does science play in response?

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What is a Natural Hazard/Disaster?

• A natural hazard is a natural process that has
  the potential for significant human impacts.
• A natural disaster is the occurrence of a natural
  event with significant human and social impacts.

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Types of Natural Hazards

• Events
• earthquakes, volcanoes, landslides
• hurricanes, typhoons, Noreasters, hailstorms,
  blizzards, icestorms
• droughts, heatwaves
• forest fires
• bolide impacts

• Trends
• global warming
• sea-level rise
• ground-water loss
• ozone loss
• disruption of cycles (carbon, nitrogen,
  hydrological)
• anthropogenic forcing

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Costs are increasing
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Man is a geologic force

• Anthropogenic forcing is a significant factor in
  climate change.
• Land-use practices put humans in danger.
• Human society has an impact on the Earth that is
  significant in scope and scale.

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What is scale?

• Processes have characteristic spatial and
  temporal scales
• Events/trends at one scale may be manifestations
  of events/trends at another scale

Length scale
Characteristic time scale
t
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Examples of Scale
Simple, linear processes can maintain scale
superposition. That is, the total process is
just the sum of sub-processes each with its own
scale. Complex and non-linear processes possess
complex scale interdependencies. The dynamics at
one scale can influence the dynamics at another
scale. Scale interdependencies make prediction
especially hard, since the driving forces may not
be known.
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Process interactions

• Human impacts must be aggregated
• One process can amplify impacts of another process

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What is the difference between Hazard and
Risk?

• Hazard is a process which has potential human
  impacts.
• Risk is the product of hazard and accumulated
  human assets.
• Concentration of wealth matters.

Source USGS
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Probabilistic earthquake hazard expressed as
level of ground acceleration that has a 10
chance of being exceeded in the next 50 years.
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Population is just one of the possible proxies
for quantifying human impact.
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Hazard times population is used by the USGS to
quantify RISK
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But RISK is not used to establish monitoring
facilities.....
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Risk is relative

• Developed and underdeveloped societies have
  different asset exposures.
• System effects can compound the valuation of
  risk.
• The study of risk is a social science.

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Are Natural Disasters Predictable?

• definition of prediction
• scientific approach to prediction
• Assume plate tectonic kinematic conditions apply
  to earthquake loading cycle.
• Earthquakes occur on known faults.
• In intraplate regions, earthquakes occur where
  they have occurred before.

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What is a Prediction?

• Predict an event.
• specify place, time, and size, in advance
• specify impacts, in advance
• Predict event potential
• specify zones of space and time within which
  events might occur
• specify impact scenarios

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Model-based or Empirical?

• use previous event patterns to predict new
  occurrences.
• or, develop and test a model
• characteristic earthquake model is simple but
  requires empirical calibration
• newer models are being developed which include
  non-linear effects

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Empirical studies require

• long time series
• careful identification and selection of associate
  conditions
• knowledge of the probability distribution

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Modeling studies require

• physical (or chemical) understanding of process
• representational theorems and constitutive
  relations
• realistic parameterizations
• ability to model complexity, chaos, and
  non-linearity if needed.

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Some time series are more predictable than
others....
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Random Noise adds Ambiguity
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Plate tectonic theory is more space-predictable
than time-predictable on human time scales.
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Characteristic Earthquake Model

• apply plate tectonic boundary conditions to
  earthquake cycle time scales
• assume plate tectonic loading applies to
  intraplate earthquakes
• develop characteristic recurrence times and
  recurrence-size relationships

log (number)
log (magnitude)
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Implications of Characteristic Earthquake Model
characteristic time
slip predictable
characteristic size
time predictable
time
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Characteristic earthquake assumption permits
computation of Global Hazard MapSource USGS
GSHAP Project
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WUS Fault Map Source CDMG
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