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Tuesday
Nov062012

Smoothing, unsmoothness, and stuff

Day 2 at the SEG Annual Meeting in Las Vegas continued with 191 talks and dozens more posters. People are rushing around all over the place — there are absolutely no breaks, other than lunch, so it's easy to get frazzled. Here are my highlights:

Adam Halpert, Stanford

Image segmentation is an important class of problems in computer vision. An application to seismic data is to automatically pick a contiguous cloud of voxels from the 3D seismic image — a salt body, perhaps. Before trying to do this, it is common to reduce noise (e.g. roughness and jitter) by smoothing the image. The trick is to do this without blurring geologically important edges. Halpert did the hard work and assessed a number of smoothers for both efficacy and efficiency: median (easy), Kuwahara, maximum homogeneity median, Hale's bilateral [PDF], and AlBinHassan's filter. You can read all about his research in his paper online [PDF]. 

Dave Hale, Colorado School of Mines

Automatic fault detection is a long-standing problem in interpretation. Methods tend to focus on optimizing a dissimilarity image of some kind (e.g. Bø 2012 and Dorn 2012), or on detecting planar discontinuities in that image. Hale's method is, I think, a new approach. And it seems to work well, finding fault planes and their throw (right).

Fear not, it's not complete automation — the method can't organize fault planes, interpret their meaning, or discriminate artifacts. But it is undoubtedly faster, more accurate, and more objective than a human. His test dataset is the F3 dataset from dGB's Open Seismic Repository. The shallow section, which resembles the famous polygonally faulted Eocene of the North Sea and elsewhere, contains point-up conical faults that no human would have picked. He is open to explanations of this geometry. 

Other good bits

John Etgen and Chandan Kumar of BP made a very useful tutorial poster about the differences and similarities between pre-stack time and depth migration. They busted some myths about PreSTM:

  • Time migration is actually not always more amplitude-friendly than depth migration.
  • Time migration does not necessarily produce less noisy images.
  • Time migration does not necessarily produce higher frequency images.
  • Time migration is not necessarily less sensitive to velocity errors.
  • Time migration images do not necessarily have time units.
  • Time migrations can use the wave equation.
  • But time migration is definitely less expensive than depth migration. That's not a myth.

Brian Frehner of Oklahoma State presented his research [PDF] to the Historical Preservation Committee, which I happened to be in this morning. Check out his interesting-looking book, Finding Oil: The Nature of Petroleum Geology

Jon Claerbout of Stanford gave his first talk in several years. I missed it unfortunately, but Sergey Fomel said it was his highlight of the day, and that's good enough for me. Jon is a big proponent of openness in geophysics, so no surprise that he put his talk on YouTube days ago:

The image from Hale is copyright of SEG, from the 2012 Annual Meeting proceedings, and used here in accordance with their permissions guidelines. The DOI links in this post don't work at the time of writing — SEG is on it. 

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Reader Comments (6)

3 Thoughts

1. Yeah that poster is pretty good, I'll have to take a picture of it.

2. Damn, I wish I saw the Claerbout talk.

3. The two BE talks in the morning INT Session was pretty good. Gary Wu, really understands how the process works way better then their sales people. Then having Kurt Marfurt show how useful it was for geobody work was pretty impressive. Also the talk right after it about using an HSV color bar for spec decomp was pretty good.

November 6, 2012 | Unregistered CommenterToastar

On Dave Hale, automatic fault detection, conical up fault geometry... Hmmm, what about migration operator artifacts? Though if anyone would know one, it should be Dave Hale.

(my first ever blog comment)

November 8, 2012 | Unregistered CommenterDavid D'Amico

@Toastar: I wish I'd seen the BE talk, though I'm a skeptic. Geotrace seem to have their signal processing act together. It's just so rare to see anyone show improved well ties in the BE'd seismic — I see Yu has something at least in his paper, but I'd want to see much more than just a tie with, 'Look how nice it is.' Maybe he did that.

@David: Thanks for the comment! It does look as if there's displacement across these surfaces — they aren't cutting through the data. you can get the data yourself if you're curious

November 8, 2012 | Registered CommenterMatt Hall

Hi Matt,
Mauricio sent me the link to Claerbout's presentation today (http://sepwww.stanford.edu/sep/jon/JonSEG2012.pdf) we are still discussing it.

I enjoyed this talk. I was in the same session worried having Mirko van der Baan and Jon Claerbout before my talk but everything went well, the public was still connected with the previous talks :-). Claerbout pointed out something related with your post about the conference system. He said that from the time he submitted the abstract to the presentation he got more interesting results. Well, he actually said that the abstract was wrong and he will be presenting a totally new result. It was a relaxing lecture, thank you for posting the youtube link.
It is good that you are connected with Laurent Duval, I gave him the link to your posts on Tuesday. Following both of you I have the perfect sources of information from Geophysics and Signal Processing. Thank you and keep posting.

Cheers,
Henry

November 9, 2012 | Unregistered CommenterHenry

@Henry: I love hearing about how our networks connect like this — thank you for the story of how things are getting passed around.

I'll definitely try to keep up the signal processing stuff, but for me it's very much just part of my own learning experience. I want to do a tutorial on random sampling and compressive sensing soon — I might have to ask you for help!

November 10, 2012 | Registered CommenterMatt Hall

Hello Matt and Evan,
Have a look at the ICASSP conference. This is one of the strongest conferences on Signal Processing and it will be held in Vancouver.
I know this one is out of your regular circuit, but it would be interesting to see pure and applied signal processing.
The deadline for submission of Regular Papers is Nov 30th.
http://www.icassp2013.com

I am not sure if I could be of any help on those topics for the tutorial. I will suggest Ismael Vera for that. He is a former PhD student in Mauricio's group. His PhD thesis was on compressive sensing with amazing results.
Henry

November 10, 2012 | Unregistered CommenterHenry

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