Hi Thanks for all the advice and references.
Dhananjay, the paper from Reid et al was helpful. I hadn't considered going back to those older papers by Nabighian, so I will check those out as well. Ed, the papers from Philips that I found had good examples of comparing different methods and source types. Specifically I found this one most useful, for anyone that is interested: Locating magnetic contacts: a comparison of the horizontal gradient, analytic signal, and local wavenumber methods, SEG 2000. Steve, the forward modelling approach sounds like a good way of testing the results. Some projects have so little information I was hoping to use depth estimate methods to help construct forward models, but that sounds like a good way of checking which method is most suitable. I still haven't found very many papers specifically using gravity. I did try the horizontal gradient method with SI=0 for thin density sheet and the HGM of the vertical derivative with SI=-1 for a vertical contact using the USGS GX. Does anyone use Euler for gravity grids? What SI would you use for a dipping or sub-vertical contact? The paper by Reid says -1, but I don't think I can set it to be less than 0 On Fri, May 1, 2015 at 11:55 AM, edcunion <[email protected]> < [email protected]> wrote: > Some examples of usgs mag-grav depth determination results are > illustrated from a handful of Jeff Phillips papers on these methods. These > are available as pdfs from different web sources. I've used older manual > graphical rule of thumb methods as crosschecks on these using a profile or > two usually for larger aeromag datasets. > > > > Ed Cunion > > > > Sent from my T-Mobile 4G LTE device > > > > > > ------ Original message------ > > *From: *Dhananjay Ravat > > *Date: *Fri, 5/1/2015 11:21 AM > > *To: *Geosoft Oasis montaj and Target; > > *Subject:*Re: [geonet] Depth to source methods > > > Hi, I presume all the potential field books have been looked into for > methodological details and a lot of useful advice. This article below, and > references therein, is a good place to start for the Euler method, if not > already read. For inclined contacts 2D analytical signal, carefully paying > attention to Misac Nabighian’s (1972, 1974 Geophysics) use for thin sheets > and trapezoids expressions and when to use anomaly and when to use its > gradient will be helpful, and also the bell-shaped 2D analytic signal and > their depth relationships will be helpful in determining parameters of > interest. I know those papers have a lot of math, but I have found it very > worthwhile struggling through that to understand what and why. Finally, in > window based methods, there will always be a tradeoff between the size of > the window, resolution, and noise in the data. Similarly, noise in the > data vs the use of methods that require higher order derivatives should be > a consideration as I am sure you know. I have found it useful to compare > results from compatible methods as you are doing. I hope this is useful. > Best wishes, -tiku > > GEOPHYSICS, VOL. 79, NO. 4 (JULY-AUGUST 2014); P. J61–J66, 3 FIGS., 1 > TABLE. 10.1190/GEO2013-0235.1 The structural index in gravity and > magnetic interpretation: Errors, uses, and abuses by Alan B. Reid1 and > Jeffrey B. Thurston2 > _____________________________ > D. Ravat | Professor of Geophysics > Earth & Environmental Sciences | Physics & Astronomy > University of Kentucky > 101 Slone Research Building | Lexington, KY 40506-0053 > fax: +1 859 323 1938 > > Web: > http://ees.as.uky.edu/users/drava2 > https://www.researchgate.net/profile/Dhananjay_Ravat/ > https://ees.as.uky.edu/gravity-magnetics-heat-flow-tectonics > https://ees.as.uky.edu/near-surface-geophysics > _____________________________ > > > > > > > On May 1, 2015, at 12:25 PM, Doug Perkin <[email protected]> < > [email protected]> wrote: > > Hi > > I have been trying various source depth estimation methods for grids of > potential field data and wanted to start a discussion on which methods tend > to provide better solutions for gravity vs aeromag. I am usually > interested in sub vertical or dipping contacts, so for magnetics I have > tried a structural index of 0 or 1 and for Gravity I have tried 0 and -1 > using the USGS special function depth analysis GX. I have also tried Euler > with various window sizes. > > The local wavenumber method using the USGS GX was interesting because it > actually provides estimates of the structural index for various anomalies; > however that method tended to give a lot more noise and was in places > giving me a structural index of 3 when the RTP grid clearly did not look > like a magnetic dipole source. > > Does anyone have experience with these depth estimation methods? Which > methods tend to give more reliable solutions for a vertical or dipping > contact using aeromag? And which methods tend to provide better solutions > for a vertical or dipping contact using gravity? Any advice or discussion > on these methods would be much appreciated > > Regards, > Doug > > > > --- > > Forum archives can be accessed here: > http://lyris.geosoft.com/read/?forum=geonet > <http://lyris.geosoft.com/read/?fourm=geonet> > > You are currently subscribed to geonet as: [email protected]. > > To subscribe or unsubscribe from any of our forums, select the User Forum > selection on the Geosoft Community page: > <http://www.geosoft.com/support/community/forums/register/> > http://www.geosoft.com/support/community/forums/register/ > <http://www.geosoft.com/support/community/forums/register/> > > > --- > > Forum archives can be accessed here: > http://lyris.geosoft.com/read/?forum=geonet > <http://lyris.geosoft.com/read/?fourm=geonet> > > You are currently subscribed to geonet as: [email protected]. > > To subscribe or unsubscribe from any of our forums, select the User Forum > selection on the Geosoft Community page: > <http://www.geosoft.com/support/community/forums/register/> > http://www.geosoft.com/support/community/forums/register/ > <http://www.geosoft.com/support/community/forums/register/> > > --- > > Forum archives can be accessed here: > http://lyris.geosoft.com/read/?forum=geonet > <http://lyris.geosoft.com/read/?fourm=geonet> > > You are currently subscribed to geonet as: [email protected]. > > To subscribe or unsubscribe from any of our forums, select the User Forum > selection on the Geosoft Community page: > http://www.geosoft.com/support/community/forums/register/ > --- Forum archives can be accessed here: http://lyris.geosoft.com/read/?forum=geonet You are currently subscribed to geonet as: [email protected]. 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