## Re: GEOSTATS: modeling zonal anisotropy

Expand Messages
• ... You can ``fake zonal anisotropy by geometric anisotropy. I think both Isaaks&Srivastava (Applied Geostatistics) and Deutsch&Journel (GSLIB) write about
Message 1 of 3 , Jul 17, 1997
• 0 Attachment
Chaosheng Zhang wrote:
>
> Dear colleagues,
>
> Question: How to model the variograms of a zonal anisotropy?
>
> I'm dealing with an area of 75km*75km, with heavy metal contents in 747
> samples. The samples are quite evenly distributed, and high
...
> ---------------------------------------------------------
> Direction Model Nugget Sill Range(km)
> ---------------------------------------------------------
> Omni Gaussion 0.03 0.13 40
> 5 (E-W) Gaussion 0.03 0.10 40
> 50 (NE-SW) Gaussion 0.03 0.21 40
> 95 (N-S) Gaussion 0.03 0.14 40
> 140(NW-SE) Gaussion 0.03 0.07 40
> ---------------------------------------------------------
You can ``fake'' zonal anisotropy by geometric anisotropy.
I think both Isaaks&Srivastava (Applied Geostatistics) and

In your example: model the variogram as the sum of:
1. a nugget (.03)
2. a Gaussian model (partial sill 0.04 to fit NW-SE, range 40)
3. some model with geometric anisotropy with:
a. the principal direction in NW-SE
b. a long range in this direction (e.g. 40000 km.)
c. an anisotropy ratio that will give it a range of 40 km
in the NE-SW direction (e.g. 0.001)
d. a partial sill, equal to 0.21-(0.03+0.04)=0.14
Note that steps b and c are related: range * anis.ratio should

You will not exactly reproduce both the 0.10 and 0.14, but
hopefully end up with a reasonable average. Tweeking with
different variogram models in 3. might help.

Good luck,
--
Edzer
--
*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!
Your message has been successfully submitted and would be delivered to recipients shortly.