Undersampling power-law size distributions: effect on the assessment of extreme natural hazards

Natural Hazards
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Abstract

The effect of undersampling on estimating the size of extreme natural hazards from historical data is examined. Tests using synthetic catalogs indicate that the tail of an empirical size distribution sampled from a pure Pareto probability distribution can range from having one-to-several unusually large events to appearing depleted, relative to the parent distribution. Both of these effects are artifacts caused by limited catalog length. It is more difficult to diagnose the artificially depleted empirical distributions, since one expects that a pure Pareto distribution is physically limited in some way. Using maximum likelihood methods and the method of moments, we estimate the power-law exponent and the corner size parameter of tapered Pareto distributions for several natural hazard examples: tsunamis, floods, and earthquakes. Each of these examples has varying catalog lengths and measurement thresholds, relative to the largest event sizes. In many cases where there are only several orders of magnitude between the measurement threshold and the largest events, joint two-parameter estimation techniques are necessary to account for estimation dependence between the power-law scaling exponent and the corner size parameter. Results indicate that whereas the corner size parameter of a tapered Pareto distribution can be estimated, its upper confidence bound cannot be determined and the estimate itself is often unstable with time. Correspondingly, one cannot statistically reject a pure Pareto null hypothesis using natural hazard catalog data. Although physical limits to the hazard source size and by attenuation mechanisms from source to site constrain the maximum hazard size, historical data alone often cannot reliably determine the corner size parameter. Probabilistic assessments incorporating theoretical constraints on source size and propagation effects are preferred over deterministic assessments of extreme natural hazards based on historic data.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Undersampling power-law size distributions: effect on the assessment of extreme natural hazards
Series title Natural Hazards
DOI 10.1007/s11069-013-1024-0
Volume 72
Issue 2
Year Published 2014
Language English
Publisher International Society for the Prevention and Mitigation of Natural Hazards
Publisher location Dordrecht
Contributing office(s) Pacific Coastal and Marine Science Center
Description 31 p.
First page 565
Last page 595
Online Only (Y/N) N
Additional Online Files (Y/N) N