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GEOSTATS: Geostat: Program for Bimodal distribution.

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  • Eunjeong Seok
    Could you post this, please. Thanks. Hi.. I am struggling with an aperture data set of a fracture plane, which shows a bimodal distribution. I have tried
    Message 1 of 3 , Mar 21, 2000
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      Could you post this, please. Thanks.

      Hi..

      I am struggling with an aperture data set of a fracture plane, which shows a
      bimodal distribution.

      I have tried Kriging and Gaussian simulation (GSLIB) to recover the aperture
      structure, but it seems not to maintain both variogram and mean and variance
      of the samples at the same time .

      Therefore, I wonder if there is any software which is able to deal with
      bimodal distribution, and
      If GSLIB is a right way to go, what kind of consideration do I need and
      which program is the most appropriate?

      Thank you in advance..

      Eunjeong..
      ------------------------
      Eunjeng Seok
      Dept. of Earth Sciences
      Memorial Univ. of NFLD
      St. John's, Canada
      Tel: 1-709-739-7270


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    • Pierre Goovaerts
      Hello, Bimodal distributions usually indicate the existence of two populations, and a Gaussian approach is likely not the most appropriate. You could try an
      Message 2 of 3 , Mar 22, 2000
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        Hello,

        Bimodal distributions usually indicate the
        existence of two populations, and a Gaussian
        approach is likely not the most appropriate.
        You could try an indicator approach but don't
        expect a better reproduction of histogram and semivariogram.
        Note that because of the back-transform and provided
        that in the normal space your simulated values follow a standard
        normal distribution, the histogram of simulated sGs values
        should be close to the sample histogram. Large ergodic
        fluctuations (deviations between realization and
        sample statistics) could be due to a large range
        of the semivariogram with respect to the size of
        the domain to be simulated?

        If you really want to generate maps reproducing all the
        statistics you mention, try simulated annealing
        (sasim program in Gslib).

        Pierre Goovaerts
        <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

        ________ ________
        | \ / | Pierre Goovaerts
        |_ \ / _| Assistant professor
        __|________\/________|__ Dept of Civil & Environmental Engineering
        | | The University of Michigan
        | M I C H I G A N | EWRE Building, Room 117
        |________________________| Ann Arbor, Michigan, 48109-2125, U.S.A
        _| |_\ /_| |_
        | |\ /| | E-mail: goovaert@...
        |________| \/ |________| Phone: (734) 936-0141
        Fax: (734) 763-2275
        http://www-personal.engin.umich.edu/~goovaert/

        <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>


        On Wed, 22 Mar 2000, Eunjeong Seok wrote:

        > Could you post this, please. Thanks.
        >
        > Hi..
        >
        > I am struggling with an aperture data set of a fracture plane, which shows a
        > bimodal distribution.
        >
        > I have tried Kriging and Gaussian simulation (GSLIB) to recover the aperture
        > structure, but it seems not to maintain both variogram and mean and variance
        > of the samples at the same time .
        >
        > Therefore, I wonder if there is any software which is able to deal with
        > bimodal distribution, and
        > If GSLIB is a right way to go, what kind of consideration do I need and
        > which program is the most appropriate?
        >
        > Thank you in advance..
        >
        > Eunjeong..
        > ------------------------
        > Eunjeng Seok
        > Dept. of Earth Sciences
        > Memorial Univ. of NFLD
        > St. John's, Canada
        > Tel: 1-709-739-7270
        >
        >
        > ______________________________________________________
        > Get Your Private, Free Email at http://www.hotmail.com
        >
        > --
        > *To post a message to the list, send it to ai-geostats@....
        > *As a general service to list users, please remember to post a summary
        > of any useful responses to your questions.
        > *To unsubscribe, send email to majordomo@... with no subject and
        > "unsubscribe ai-geostats" in the message body.
        > DO NOT SEND Subscribe/Unsubscribe requests to the list!
        >

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      • Romijn, R.
        Message 3 of 3 , Mar 23, 2000
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          Re: GEOSTATS: Geostat: Program for Bimodal distribution.

          Dear Eunjeong Seok,

          A semivariogram of a bimodal distribution reflects two kinds of variances: 1) the spatial variance between the sample points and 2) the variance between the two populations which form the bimodel distribution. The spatial variance is therefore contaminated with the variance between the two populations.

          One thing you can do is try to identify the factors related to these two populations. When these factors are determined (e.g. mineral composition, direction etc. ) you can correct your data points in such a way the distribution becomes unimodal. A semivariogram of this unimodal distribution wil reflect the spatial variance with less contamination. For the new variogrammodel GSlib is appropriate.

          A second way to handle the problem is simply to do two interpolations of the datapoints of the two populations separately and then subsequently combine these two interpolation results. The drawback of this method is that the number of datapoints per interpolation will be reduced.

          Good luck,


          Guido Ypenburg

          _____________________________________________________

          G.C. Ypenburg
          Engenering department
          Public Works Rotterdam
          Hydrogeology and geostatistics
          EPIV-2.22
          Galvanistraat 15
          PO box 6633
          3002 AP Rotterdam
          tel:    +31 10-489 54 97
          fax:    +31 10-489 45 00


            ----------
            Van:    Pieters, G.
            Verzonden:      woensdag 22 maart 2000 8:35
            Aan:    Ypenburg, G.
            Onderwerp:      FW: GEOSTATS: Geostat: Program for Bimodal distribution.



            ----------
            Van:    Eunjeong Seok[SMTP:ESEOK@...]
            Verzonden:      woensdag 22 maart 2000 4:49:34
            Aan:    ai-geostats@...
            Onderwerp:      GEOSTATS: Geostat: Program for Bimodal distribution.
            Automatisch doorgezonden door een regel

            Could you post this, please. Thanks.

            Hi..

            I am struggling with an aperture data set of a fracture plane, which shows a
            bimodal distribution.

            I have tried Kriging and Gaussian simulation (GSLIB) to recover the aperture
            structure, but it seems not to maintain both variogram and mean and variance
            of the samples at the same time .

            Therefore, I wonder if there is any software which is able to deal with
            bimodal distribution, and
            If GSLIB is a right way to go, what kind of consideration do I need and
            which program is the most appropriate?

            Thank you in advance..

            Eunjeong..
            ------------------------
            Eunjeng Seok
            Dept. of Earth Sciences
            Memorial Univ. of NFLD
            St. John's, Canada
            Tel: 1-709-739-7270


            ______________________________________________________
            Get Your Private, Free Email at http://www.hotmail.com

            --
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            *As a general service to list users, please remember to post a summary
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