Talk:Fault (geology)

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[edit] webpage on faults

When I visited the webpage http://www.wikipedia.org/wiki/Geologic_fault, I was very glad that I had finally found a webpage on faults, but I was really confused by the language. Something that a long-ago English teacher once said to me: When you answer an essay question, tell all the facts you know, make the answer as complete as possible. Then say what that means. ex. "The Earth is an oblate sphere. THIS MEANS that the Earth is a sphere, but because of the fact that it spins on an axis, centripical force flattens the poles and pushes out the center. A good way for you and I to understand what this means is by thinking of a popular toy much like a yo-yo. This toy is a, viscous disk about 1 cm thick and 4cm in diameter. It is attached to two strings coming out of either side. One twists these strings, then untwists them with a flick of the wrists, repeating this motion until the circle blurs, appearing bigger than it is. In truth, it is not an illusion, but that the centripical force has pulled the edges of the disk out with material taken from the top and bottom of the disk, forcing it to squish in. This is how the Earth acts." I am not saying that the explanation of each fact should be as complete as this one– no, for that much information would be much too much. However, in the way that this explanation makes you understand (or at least tries to), you don't have to be comfortable with scientific language. If you understand the part quoted about the toy, you don't even have to be able to think abstractly. I think that your geography page could do well to be written in some way more similar to this.

It's a geology page, rather than a geography page, but fair point. Will have another crack at it. charlieF

[edit] Hangingwall/Footwall

I am (was) trying to learn about terminology of structural geology. I found this web page and read it, and thought I understood it. Then I visited another site, the Schlumberger oilfield services oilfield glossary page about faults. I thought I understood what a hanging wall was from this page since I could grasp the concept of 'the block above the fault' easily. What I mean is that I had an 'intuitive' feeling for the concept of a fault plane (as long as it wasn't vertical) and could easily grasp the idea of the block above this plane and the one below it. Then I went back to this page and realised that according to the Schlumberger definition what is called the hanging wall here I would call the footwall and vice versa. I don't understand why. Don't forget I'm an amateur and could be missing something obvious.

I'm pretty sure the caption on the picture is backwards and the Schlumberger source is correct. Can anyone think of a quick fix? -- Walt Pohl 16:56, 17 Mar 2004 (UTC)
I agree. I can't find a web page that agrees with our picture, so I swapped the labels. -- Heron 21:24, 17 Jul 2004 (UTC)

I hope that the mining origin of the terms helps people, it sure helped me Mikenorton 16:49, 15 October 2006 (UTC)

[edit] integration

Text copied from newly created article 'Faults'. Maybe there is something that ought to be integrated into the article:

A fault is a fracture in the crust of the earth that has caused displacement (offset) of the crust. Faults may offset soil or rock materials on either side of the fault plane for distances ranging from less than a few inches to distances on the order of hundreds of miles. Faults are usually associated with past or present tectonic movement, seismic activity (earthquakes), and volcanic activity. Faults may be quite old features (having displaced rocks millions of years old) to recent features that have displacement rocks within historic times. Faults may be too old since their last displacement to be of concern to man, whereas recently active faults, particularly those faults associated with recent large earthquakes, can be a significant hazard to man.

- snoyes 11:35, 5 Jul 2004 (UTC)

[edit] Reverse fault same as thrust fault?

Some texts, unlike our article, make a distinction between reverse fault and a thrust fault. A reverse fault is the exact opposite of a normal fault, while a thrust fault is the slippage of two strata past each other under horizontal compression. Is this distinction generally accepted? -- Heron 21:40, 17 Jul 2004 (UTC)

Many structural geologists would use "thrust fault" for a compressive fault dipping LESS than 45 degrees and "reversed fault" for a compressive fault dipping MORE than 45 degrees. User:Denbrok

Thrust faults, as Denbrok said, are shallow-dipping. They also have other distinguishing features from reverse faults, in that they occur within units; ramp up through units; may be associated with fold-bend folds, etc etc.Rolinator 02:38, 20 December 2005 (UTC)

Depending on who you ask the amount of dip at which a thrust fault is called reverse fault and vise versa varies. a common value is 35 degrees. EndoSimon 12:12, 16 April 2007 (UTC)

[edit] Merges

I think transform fault and thrust fault should be merged into this article. If they get too big, they can be split off again. -- Kjkolb 03:39, 16 December 2005 (UTC)

I think not; they are too different in terms of their sense of throw and geologic setting. Thrust faults are not at all like transform faults.Rolinator 02:36, 20 December 2005 (UTC)

I know they are very different, but normal faults, reverse faults, strike-slip faults and oblique-slip faults are covered here and don't have articles of their own. Transform fault is only a paragraph and one sentence long and thrust fault is two paragraphs long, and the second paragraph is small. Both are shorter than the dip-slip fault section of this article even without the pictures. -- Kjkolb 08:30, 20 December 2005 (UTC)

No, let's keep them separate. Both thrust faults and transform are distinctly different from other fault types and each other. They describe totally differing geologic processes and the articles for each need considerable expansion - definetly not merging. Vsmith 03:30, 21 December 2005 (UTC)

That's fine. It just seems weird to have some fault types split off, while other major types are included in the article, especially when the articles are so short. I'll remove the tags. -- Kjkolb 06:17, 21 December 2005 (UTC)

[edit] Duplexes, ramp-flat, klippe

I have added throw, heave, etc. Added duplexes and klippe. I'm lacking decent open-source diagrams for these, especially the ramp-flat ones.

[edit] Parallel Faults

I was reading about dip-slip faults, and got confused about the use of the word "parallel". It seems that the author means parallel at the surface. I looked at the linked articles for horst and graben, and found the same reference to "parallel" faults, but the fault planes are not parallel, only the intersection of the planes with the surface. Is this a standard accepted use of this word in this context? Also, as a geology neophite, I wonder if three or more faults could produce the same effect as a horst or graben, without even the intersection of the faults and the surface being parallel?

Yeah. Imagine a graben within a graben. In fact, that's what happens pretty much all of the time, since faults always come in sets. "Parallel" must indeed refer to the intersection of the fault plane with the surface, but even then it's not a precise term. A horst or graben can be between two fault planes which do not have parallel strikes... just so long as they're roughly parallel and not, like, perpendicular.

I added the dip directions of the two faults in the horst and graben definitions and then decided that the use of "parallel" became unnecessary. Mikenorton 16:52, 15 October 2006 (UTC)

[edit] syndepositional faulting

Editing something else. Need to put SynDep faulting onto the To-Do list. Really needs a diagram to help.

[edit] Images

The amount of images people have taken of "a fault in the wilderness" is flattering as to the importance of this page, but the following image, in thumbnal, is pretty much useless as far as a clearly legible depiction of faulting goes, so I have removed it from the page;

Relative Motion
Relative Motion

This is not to say it isn't a good photo, but for illustration purposes we need things which are clearly identifiable as faults even in thumbnail size.Rolinator 23:52, 26 October 2006 (UTC)

[edit] Thrust / Reverse faults definition incoherent with pictures?

There must be a slight inversion here. In one of the pictures, a reverse fault is shown, but labelled "thrust fault". In another one both names are used. This perhaps may be changed for a clearer version.


[edit] Requested move

Geologic fault → Fault (geology)

  • You won't find the term "geologic fault" in any dictionary or other encyclopedia. In keeping with general naming style in wikipedia I'd suggest changing the name of the article to "Fault (geology)" (with redirect from geologic fault). If no discussion I'll do this soon. --Zamphuor 13:49, 21 April 2007 (UTC)

[edit] Discussion

  • Support: This is a sensible suggestion. (John 14:21, 21 April 2007 (UTC))
  • Support: Term used exclusively by geologists and geological engineers; give'r. +mwtoews 02:03, 22 April 2007 (UTC)
  • Support: "Geological fault" redirects to this page so Zamphuor's suggestion would be a good plan - either that or I think the fact that this term is also used to describe this feature needs to be incorporated into the article. --Vertilly 12:15, 20 May 2007 (UTC)
  • Support. Neither the phrase geological fault nor geologic fault is common English, rather the context indicates that this is the meaning, so this is a standard case of disambiguation. Andrewa 03:09, 13 August 2007 (UTC)
  • Support Sdornan 03:12, 14 August 2007 (UTC)
  • Support Rolinator 05:09, 14 August 2007 (UTC)
  • Support per nom Reginmund 01:37, 15 August 2007 (UTC)

Moved per consensus. Will fix double redirs. now. Vsmith 02:56, 15 August 2007 (UTC)

[edit] Mitigation

I'm not sure what this section is doing in this article, this is covered better by the pages on Seismic hazard and Mitigation of seismic motion. Unless anyone objects, I'm just going to add these links to the See Also section and remove Mitigation.Mikenorton 08:22, 15 August 2007 (UTC)

No objections, so section removed. Mikenorton 16:06, 16 September 2007 (UTC)

[edit] fault plane

This topic is in some kind new to me, but as I have not found any article mention 'focal mechanism' I would suggest that an article should be created and 'fault plane' should lead there or should be the article title, which in the latter case treats 'focal mechanism' as well. Ausgerechnet alaska 02:20, 15 September 2007 (UTC)

INCLUDE EXAMPLE OF NORMAL FAULT