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Friday
Sep232011

## News of the week

A quick round up of geosciencey tech news at the end of a busy week at SEG.

### Mmm, open source

Visualization company Kitware, makers of open source viz software Paraview, have released a new version of VTK, their toolkit for developers. Version 5.8 has new and improved Python wrappers and support for openGL inside documents. They are also offering free online courses for much of their technology. If you don't know their stuff, now's the time to check it out!

### Real-time data toolbox

Twitter and geophysics? Maybe: they announced some open source goodness this week with their Storm library for real-time analysis of massive data streams. They developed it for analysing breaking news and global events, but we think it might have application in all kinds of real-time data processing problems like microseismic and production monitoring. Find the project on GitHub.

### Not just another software company?

Dynamic Graphics, a small California company, caught our eye. Their low profile seems about to change, as their 'quantitative visualization' software looks ready to compete with anyone. Their focus on 4D and well-planning pits them against outfits like Transform Software, Down Under GeoSolutions, and of course all the usual suspects.

### Learn Python!

Enthought are the leaders in scientific programming and especially support for Python, as well as on-demand development. They now offer a regular Python programming course just for geophysicists, and tour all over the world with it. The next edition is in Houston, 2–4 November. If you ever wanted to dabble with code, this is your chance: Python is easy to learn and very powerful.

This regular news feature is for information only. We aren't connected with any of these organizations, and don't necessarily endorse their products or services. Python is a trademark of the Python Software Foundation. ParaView and VTK are trademarks of Kitware. Storm is a trademark of Twitter, Inc.

Friday
Sep092011

## News of the week

### Dips from pics

In collaboration with the Geological Survey of Canada, Pangaea Software have built a very nifty tool, Orion, for computing dip from satellite images and digital elevation models. With these two pieces of data, and some assumptions about scale, it's possible to deduce the dip of strata without getting your boots muddy. Matt heard all about this tool from the GSC collaborator, Paul Budkewitsch, at the 3P Arctic conference in Halifax last week; here's their abstract

### Ocean bottom investment

CGGVeritas has made a commitment to manufacture 800 new Trilobit four-component deepwater nodes for seismic acquisition, to add to its existing pool. The device has three oriented accelerometers plus a hydrophone in addition to an onboard battery and recording system. This all-in-one design can be deployed on the seabed by most ROVs, making it easy to place near platforms and other infrastructure that towed streamer and cable systems cannot access.

Arguably the industry leader in cableless systems is FairfieldNodal, who are already deploying more than a thousand nodes. It's great to see a big player like CGGVeritas coming to compete with this potentially transformative technology.

### Update for Insight Earth

Colorado-based software company TerraSpark has just announced the release of Insight Earth 1.6, an integrated volume interpretation tool. Enhancements include a more interactive data import and export interface, improved velocity modeling, and upgrades to the automated fault extraction. In a January post, Evan highlighted an article by Stan Hammon of TerraSpark on the computational and psychological factors affecting intellegent design. It's inspired stuff.

### Re-introducing SubSurfWiki

AgileWiki is now SubSurfWiki, at subsurfwiki.org. Please change your bookmarks! We felt that it was a little too Agile-centric and want to appear as open web-space for anything subsurface. We want it to grow, deepen and diversify, and above all be useful. So check it out and let us know if you have any feedback on utility, appearance and content.

More news... If you like this, check out previous news posts from Agile*

Orion is a trademark of Pangaea Software. Insight Earth is a trademark of TerraSpark. SubSurfWiki is a trademark of Agile Geoscience. The satellite image is copyright of Google. This regular news feature is for information only. We aren't connected with any of these organizations, and don't necessarily endorse their products or services.

Monday
Aug222011

## Beyond the experts

I presented a poster at the 1IWRP, and it was certainly a change in tone from the technical rigor of most other talks. Since I had a good discussion at the break with a number of people, I thought I would make a video out of it. If you've got six minutes, you can check it out:

In the video I make reference to a few other topics we've touched on earlier on the blog:

I hope to be getting into making more videos soon, so let me know if you like the format, and if you have any suggestions.

Friday
Jul082011

## Tuning geology

It's summer! We will be blogging a little less often over July and August, but have lots of great posts lined up so check back often, or subscribe by email to be sure not to miss anything. Our regular news feature will be a little less regular too, until the industry gets going again in September. But for today... here's the motivation behind our latest app for Android devices, Tune*.

Geophysicists like wedges. But why? I can think of only a few geological settings with a triangular shape; a stratigraphic pinchout or an angular unconformity. Is there more behind the ubiquitous geophysicist's wedge than first appears?

Seismic interpretation is partly the craft of interpreting artifacts, and a wedge model illustrates several examples of artifacts found in seismic data. In Widess' famous paper, How thin is a thin bed? he set out a formula for vertical seismic resolution, and constructed the wedge as an aid for quantitative seismic interpretation. Taken literally, a synthetic seismic wedge has only a few real-world equivalents. But as a purely quantitative model, it can be used to calibrate seismic waveforms and interpret data in any geological environment. In particular, seismic wedge models allow us to study how the seismic response changes as a function of layer thickness. For fans of simplicity, most of the important information from a wedge model can be represented by a single function called a tuning curve.

In this figure, a seismic wedge model is shown for a 25 Hz Ricker wavelet. The effects of tuning (or interference) are clearly seen as variations in shape, amplitude, and travel time along the top and base of the wedge. The tuning curve shows the amplitude along the top of the wedge (thin black lines). Interestingly, the apex of the wedge straddles the top and base reflections, an apparent mis-timing of the boundaries.

On a tuning curve there are (at least) two values worth noting; the onset of tuning, and the tuning thickness. The onset of tuning (marked by the green line) is the thickness at which the bottom of the wedge begins to interfere with the top of the wedge, perturbing the amplitude of the reflections, and the tuning thickness (blue line) is the thickness at which amplitude interference is a maximum.

For a Ricker wavelet the amplitude along the top of the wedge is given by:

$A(t) = R(1-(1-2 \pi^2 f^2 t^2) e^{-\pi^2 f^2 t^2})$

where R is the reflection coefficient at the boundary, f is the dominant frequency and t is the wedge thickness (in seconds). Building the seismic expression of the wedge helps to verify this analytic solution.

### Wedge artifacts

The synthetic seismogram and the tuning curve reveal some important artifacts that the seismic interpreter needs to know about, because they could be pitfalls, or they could provide geological information:

Bright (and dim) spots: A bed thickness equal to the tuning thickness (in this case 15.6 ms) has considerably more reflective power than any other thickness, even though the acoustic properties are constant along the wedge. Below the tuning thickness, the amplitude is approximately proportional to thickness.

Mis-timed events: Below 15 ms the apparent wedge top changes elevation: for a bed below the tuning thickness, and with this wavelet, the apparent elevation of the top of the wedge is actually higher by about 7 ms. If you picked the blue event as the top of the structure, you'd be picking it erroneously too high at the thinnest part of the wedge. Tuning can make it challenging to account for amplitude changes and time shifts simultaneously when picking seismic horizons.

Limit of resolution: For a bed thinner than about 10 ms, the travel time between the absolute reflection maxima—where you would pick the bed boundaries—is not proportional to bed thickness. The bed appears thicker than it actually is.

Bottom line: if you interpret seismic data, and you are mapping beds around 10–20 ms thick, you should take time to study the effects of thin beds. We want to help! On Monday, I'll write about our new app for Android mobile devices, Tune*.

Reference

Widess, M (1973). How thin is a thin bed? Geophysics, 38, 1176–1180.

Tuesday
Jul052011

## Well worth showing off

Have you ever had difficulty displaying a well log in a presentation? Now, instead of cycling through slides, you can fluidly move across a digital, zoomable canvas using Prezi. I think it could be a powerful visual tool and presentation aid for geoscientists. Prezi allows users to to construct intuitive, animated visualizations, using size to denote emphasis or scale, and proximity to convey relevance. You navigate through the content simply by moving the field of view and zooming in and out through scale space. In geoscience, scale isn't just a concept for presentation design, it is a fundamental property that can now be properly tied-in and shown in a dynamic way.

I built this example to illustrate how geoscience images, spread across several orders of magnitude, can be traversed seamlessly for a better presentation. In a matter of seconds, one can navigate a complete petrophysical analysis, a raw FMI log, a segment of core, and thin section microscopy embedded at its true location. Explore heterogeniety and interpret geology with scale in context. How could you use a tool like this in your work?

Clicking on the play button will steer the viewer step by step through a predefined set of animations, but you can break off and roam around freely at any time (click and drag with your mouse, try it!). Prezi could be very handy for workshops, working meetings, or any place where it is appropriate to be transparent and thorough in your visualizations.

You can also try roaming Prezi by clicking on the image of this cheatsheet. Let us know what you think!

Thanks to Burns Cheadle for Prezi enthusiasm, and to Neil Watson for sharing the petrophysical analysis he built from public data in Alberta.

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