Power variograms of statistically isotropic or anisotropic fractal fields are weighted integrals of variograms representing statistically homogeneous fields (modes) having mutually uncorrelated increments. Large- and small-scale cutoffs were previ-ously assumed proportional to length scales of the sampling window and data support. We verify this assumption numerically for two-dimensional isotropic fractional Brownian motion (fBm). It was previously concluded semi-empirically that, for Hurst coefficient H = 0.25, the constant of proportionality is μ = 1/3. We confirm this but find μ to vary with mode type and H. We find that due to lack of ergodicity, sample fBm variograms generated on finite windows exhibit directional dependence and differ sharply between realizations. Many realizations are required to obtain an average sample variogram resembling the theoretical power model, especially for persistent fields. We propose generating fBm on finite windows using truncated power variograms and provide guidance for doing so effectively.

Scaling Effects on Finite-Domain Fractional Brownian Motion / Cintoli S.; S. P. Neuman; V. Di Federico. - STAMPA. - (2005), pp. 75-86. (Intervento presentato al convegno Fifth edition of the European Conference on Geostatistics for Environmental Applications - geoENV 2004 tenutosi a Neuchatel (Svizzera) nel 13-15 ottobre 2004).

Scaling Effects on Finite-Domain Fractional Brownian Motion

CINTOLI, STEFANO;DI FEDERICO, VITTORIO
2005

Abstract

Power variograms of statistically isotropic or anisotropic fractal fields are weighted integrals of variograms representing statistically homogeneous fields (modes) having mutually uncorrelated increments. Large- and small-scale cutoffs were previ-ously assumed proportional to length scales of the sampling window and data support. We verify this assumption numerically for two-dimensional isotropic fractional Brownian motion (fBm). It was previously concluded semi-empirically that, for Hurst coefficient H = 0.25, the constant of proportionality is μ = 1/3. We confirm this but find μ to vary with mode type and H. We find that due to lack of ergodicity, sample fBm variograms generated on finite windows exhibit directional dependence and differ sharply between realizations. Many realizations are required to obtain an average sample variogram resembling the theoretical power model, especially for persistent fields. We propose generating fBm on finite windows using truncated power variograms and provide guidance for doing so effectively.
2005
Geostatistics for Environmental Applications
75
86
Scaling Effects on Finite-Domain Fractional Brownian Motion / Cintoli S.; S. P. Neuman; V. Di Federico. - STAMPA. - (2005), pp. 75-86. (Intervento presentato al convegno Fifth edition of the European Conference on Geostatistics for Environmental Applications - geoENV 2004 tenutosi a Neuchatel (Svizzera) nel 13-15 ottobre 2004).
Cintoli S.; S. P. Neuman; V. Di Federico
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/40919
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