[Therion] strike and dip

[Xavier Robert]

Hi,

Maybe some ideas :

Le 10 Feb 2011 à 05:43, Stacho Mudrak a écrit :

> Hi all,
>
> we are solving a problem of adding a basic geological observations  
> (measurements) to therion.
> When measuring a planar feature (bedding or fault or others), you  
> measure strike and dip.
> When measuring linear features, trend and plunge is measured.
> In the case of faults, also whether it is dextral or sinistral fault  
> is determined and potentially a magnitude.
>
> My question is, do you have some idea/wish how to integrate these  
> into therion?

I have some experience with that as sometime I do geological/ 
microtectonic field work.

1) The easiest way I found to write these informations on a map and/or  
field book, this is to write as you wrote a T (for planes) oriented in  
regards to the strike. I am used to write the strike on the side of  
the T, and the dip at the base of the T.

For linear features, I just draw a line oriented in regards to the  
trend, with a point at the starting af the direction. I also write  
trend and plunge.

I attach to this email an example of what that gives.

For faults, this is a plan. When they are lines on the plan, I add a  
line inside the T, in regards to the side of where it plunges, and I  
write the value of the plunge. To say if it is a normal, inverse,  
dextral and/or senestral fault, one idea is maybe to write a N, I, D,  
S, ND, NS, ID or IS just above the T.


2) Another possibiliy to show these features is to use stereographic  
projections (Wulf or Schmidt diagrams), as it is usually done in  
publications (ex : http://en.wikipedia.org/wiki/File:StereoprojectStructuralgeol.jpg) 
. BUT, that means that a routine should be written to produce the  
projections. And, for someone that is not used to work with these  
data, this is very hard to read/understand. Thus, I would prefer the  
first solution.


> Do you have some experience with it?
>
> Our first idea is to add a standard T symbol for strike and dip  
> measurement, but there is one problem. Orientation of this symbol is  
> not drawn, but it is measured (with compass). But its position is  
> given by position on the map. Should these measurements be entered  
> into a table (as centerline data are), or put as options with symbols?

I do not know if it possible, but I think that for me it would be  
easier to use this symbol with options, something like :

for a plan/fault : -plan "Strike" "Dip" -fault "type" - line  
"Plunge"      (with type = N or I or D or S or ND or NS or ID or IS)
for a line : -line "Trend" "Plunge"

 From that, you build the symbol (T/line+values) and then from the  
Strike or the Trend, you rotate the symbol.

If that helps, that's great !

Cheers,

Xavier


>
> Do you have any ideas or comments?


>
> Best regards, S.
>
>
>
>
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> http://mailman.speleo.sk/mailman/listinfo/therion

--
Xavier ROBERT
CIFAR Junior Fellow
GEOTOP, Département des Sciences de la Terre et de l'atmosphère
Université du Quebec a Montréal
CP 8888, Succursale centre-ville
MONTREAL, Quebec
H3C 3P8

(1-514) 987-3000 poste 3592
xavier.robert01 at gmail.com

http://www.geotop.ca/index.php?option=com_content&task=view&id=861&Itemid=148
http://www2.cifar.ca/research/junior-academy/cifar-junior-fellows/?i=331
http://picasaweb.google.com/xavier.robert01


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