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7/26/2019 Lecture 4 Aleatory Worst Case
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CE 5603 SEISMIC HAZARD ASSESSMENT
LECTURE 4
ALEATORY vs. EPISTEMIC UNCERTAINTY
DETERMINISTIC vs. WORST CASE
By : Prof. Dr. K. nder etin
Middle East Technical University
Civil Engineering Department
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Aleatory
Variability and Epistemic
Uncertainty
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Aleatory variability is defined as the randomness in the phenomena itself. There's
no control of uncertainty in the phenomenon and the process is purely random.
Aleatory variability can not be reduced with more or better observations. One
solution to decrease aleatory variability inherent in the model may be to completely
change the model (i.e. switch from empirical observations to a physical model).
Natural randomness is modeled as a probability density function for the specificproblem being handled.
Epistemic uncertainty is due to lack of information in how the properties of the
process changes. With more data and enhanced models, epistemic uncertainty
can be reduced. Attenuations by proposed by different researchers using the same
raw sample set, and different best function fits to sample points with small numberof samples will vary the epistemic uncertainty for the problem. Figures 8-10 show
the seismic source characterizations used by various researchers in nationwide
seismic hazard mapping studies, forming a typical example for epistemic
uncertainty definition.
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Aleatory
Variability and Epistemic
Uncertainty
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Aleatory
Variability and Epistemic
Uncertainty
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Aleatory
Variability and Epistemic
Uncertainty
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Seismic Hazard Framework
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Worst Case Approach
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Mmax: Maximum Earthquake Magnitude
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Closest Distance and Maximum Ground
Motions
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Notes on Worst Case Ground Motions
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Example on Worst Case Ground Motions
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