Usually when I've seen a "wavy" semivariogram, it's because of a local feature superimposed over an existing field function - for instance, a release of mercury in a field of soil with very low "natural" mercury content. The period of the waviness is related to the distance across the feature (the width of the spill, in this case). Of course, this is nothing particularly earth-shattering, but useful none the less.
I've used semivariograms like this in the past to "guestimate" the approximate size of a plume based on sparse data. Not all geostatistics ends up in gridding and estimating at every point! Sometimes just looking at the semivariogram is very useful. Tim Glover Senior Environmental Scientist - Geochemistry Geoenvironmental Department MACTEC Engineering and Consulting, Inc. Kennesaw, Georgia, USA Office 770-421-3310 Fax 770-421-3486 Email [EMAIL PROTECTED] Web www.mactec.com -----Original Message----- From: Rajive Ganguli [mailto:[EMAIL PROTECTED] Sent: Tuesday, December 07, 2004 4:50 PM To: [EMAIL PROTECTED] Subject: [ai-geostats] variogram analysis My question is general. What do you conclude if your variogram is wavy? Cyclic patterns? I have what appears to be high nugget, followed by a wavy pattern. If you wish, here is more info: an offshore placer platinum deposit, not too many boreholes - just 29 from decades ago spanning several square kilometers. The variogram (from GEOEAS) of the grade (ln) is given in: http://www.faculty.uaf.edu/ffrg/Variogram.zip The variogram is cyclic. Goes up and down. I tried various lags/directions. I will try to dig up the geological information and see what it says. -- Rajive
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