Amplitude effects due to multiscale impedance contrasts and multiple scattering: implications for Ivrea-type continental lower crust

Douma, Huub; Roy‐Chowdhury, K.

doi:10.1046/j.1365-246x.2001.00537.x

Cited by 7 publications

(5 citation statements)

References 58 publications

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“…As Goff et al (1994) describe in their paper, during the process of making continuous OV‐fields modal, scale lengths and Hurst number get affected. These effects have been quantified in that paper, and have been verified by several authors, amongst others Douma & Roy‐Chowdhury (2001). Bimodalization of a OV‐field decreases the effective Hurst number of the resulting OV‐field by roughly a factor 1/0.5.…”

Section: Effect Of the Vertical Derivative Operatorsupporting

confidence: 74%

Underestimation of scale lengths in stochastic fields and their seismic response: a quantification exercise

Carpentier¹,

Roy‐Chowdhury²

2007

Geophysical Journal International

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S U M M A R YThe possibility that parts of the Earth's continental lower crust can be described with stochastic geological models has been suggested for some time. Recent studies of deeper well logs also indicate a possible stochastic structure at mid-crustal levels. This motivates a closer examination of the relation between the statistics of reflection wavefields and that of the lower crust. Such a relation can put important constraints on possible lower crustal models. This study follows up earlier efforts to quantify the statistics of both stochastic lower crustal models and the reflected wavefield. Since modelling of the seismic response of stochastic (von Karman) fields implies the usage of the impedance contrast field of the latter, we wish to compare the second-order statistics of both types of fields (velocity and impedance). This study concludes that the vertical derivative operator on a von Karman velocity field, implicitly present in the impedance contrast field, alters the second-order horizontal von Karman statistics of the velocity fields in a profound way. Wavefield effects, undoubtedly present in observed seismic data, which have earlier been proposed as possible causes for the aforementioned change, seem to play a secondary role. The vertical derivative operation, inherent in the impedance contrast field, reduces the estimated horizontal scale length and Hurst number by a factor of 2-22 and 1-3, respectively. Original vertical scale length and Hurst number of the velocity fields have a (quasi-)linear influence on this underestimation. Horizontal scale lengths and Hurst numbers were also estimated from the seismic response (Primary Reflectivity Section) of the von Karman fields. The values obtained are close to those obtained from the causative impedance contrast fields, and are similarly underestimated. This suggests a dominant role for the vertical derivative operator in the underestimation of horizontal scale length and Hurst number. This attempt to quantify the relation between the horizontal spatial statistics of von Karman fields and the estimates derived from their seismic response, may be useful in upscaling the latter.

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Section: Effect Of the Vertical Derivative Operatorsupporting

confidence: 74%

Underestimation of scale lengths in stochastic fields and their seismic response: a quantification exercise

Carpentier¹,

Roy‐Chowdhury²

2007

Geophysical Journal International

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“…Multiple scattering, or the transition from specular to diffractive reflectivity [ Wu and Aki , 1988], could significantly alter the lateral von Karman correlation in the reflected wavefield. For example, research by Douma and Roy‐Chowdhury [2001] investigated the amount of multiple scattering in zero‐offset wavefields reflected from a 1‐D von Karman type continental lower crust. Although they found single scattering to be a dominant process, this was only valid for a 1‐D situation.…”

Section: Relating Power Law Structure Of Medium and Wavefieldmentioning

confidence: 99%

Conservation of lateral stochastic structure of a medium in its simulated seismic response

Carpentier

Roy‐Chowdhury

2009

J. Geophys. Res.

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[1] Mapping correlation lengths of continental lower crustal heterogeneity directly from deep reflection data can be a valuable additional interpretation tool for deep seismic imaging. In this feasibility study we investigate the conservation of lateral correlation length and power law structure in the seismic response of lower-crustal stochastic lithology. The conservation of von Karman power law heterogeneity in backscattered wavefields is evaluated in a range of challenging seismic scenarios. We pay special attention to the limitations of this conservation due to the effect of spatial band limitation, caused by limited seismic recording aperture and to the effect of complex seismic scattering conditions. The comparison of average lateral correlations in von Karman media and their modeled reflection responses reveals two important facts: spatial band limitation by limited seismic illumination severely affects the estimated power law exponent (the Hurst number) of the von Karman heterogeneity distribution, but the estimated correlation length is unaffected and scales linearly with the original value. The original type of lateral power law distribution is conserved under nearly all seismic scattering conditions investigated, albeit with an underestimated correlation length and overestimated Hurst number. Our results can be quantitatively explained which allows for stable estimations of correlation length under various seismic scattering scenarios. This study confirms the potential of utilizing estimates of lateral von Karman structure to characterize the middle and lower crust from deep seismic reflection data.Citation: Carpentier, S. F. A., and K. Roy-Chowdhury (2009), Conservation of lateral stochastic structure of a medium in its simulated seismic response,

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“…As mentioned above, we use the von Karman autocorrelation function/power spectrum to describe continental lithospheric fabric. Studies by Goff and Jordan [1988], Goff et al [1994], Goff and Jennings [1999], Frenje and Juhlin [2000], Douma and Roy‐Chowdhury [2001], and Carpentier and Roy‐Chowdhury [2007] report on practical aspects of working with this function in the context of modeling lithological fabric. Three von Karman parameters are assumed to describe the fabric of the 2‐D continental lithosphere that we focus on: horizontal correlation length ( a x ), vertical correlation length ( a z ) and power law exponent ( ν ).…”

Section: Estimation Of Power Law Parametersmentioning

confidence: 99%

Delineating tectonic units beneath the Donbas Fold Belt using scale lengths estimated from DOBRE 2000/2001 deep reflection data

et al. 2009

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A novel statistical analysis, which augments conventional interpretation of deep seismic reflection/refraction data, is applied to the DOBRE 2000/2001 reflection profile. The goal is to improve delineation of the lithosphere in terms of lithotectonic units and to compare these to existing interpretations. After a successful validation of the method using synthetic data, stochastic parameters estimated from windowed average lateral autocorrelations in the DOBRE data are compiled in a two‐dimensional profile of von Karman‐type causative reflectivity. These estimates in terms of lateral correlation lengths and power law exponents are accompanied by associated uncertainties. Given its low uncertainties, the lateral correlation length ax turns out to be a robust delineator. The profile of ax reveals systematic spatial variations in the lithospheric fabric below the Donbas Fold Belt. As in earlier interpretations based upon conventional processing of reflection/refraction data, both the sedimentary basin and Moho discontinuity stand out clearly, as well as a region indicating massive vertical intrusion in the crust from upper mantle sills and ultramafic underplating of the lower crust. Notable differences with conventional interpretations include the number and extent of supra‐Moho rift pillow structures, the lack of imaging a crust‐cutting dislocation feature and a laterally disturbed uppermost mantle. Von Karman lateral correlation length provides new independent information at a scale between velocity models from wide‐angle reflection/refraction data and line drawings from near vertical reflections and provides new insights and understanding of lithospheric evolution.

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Amplitude effects due to multiscale impedance contrasts and multiple scattering: implications for Ivrea-type continental lower crust

Cited by 7 publications

References 58 publications

Underestimation of scale lengths in stochastic fields and their seismic response: a quantification exercise

Underestimation of scale lengths in stochastic fields and their seismic response: a quantification exercise

Conservation of lateral stochastic structure of a medium in its simulated seismic response

Delineating tectonic units beneath the Donbas Fold Belt using scale lengths estimated from DOBRE 2000/2001 deep reflection data

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