Are you a poet or a mathematician?

Many geologists can sometimes be rather prone to a little woolliness in their language. Perhaps because you cannot prove anything in geology (prove me wrong), or because everything we do is doused in interpretation, opinion and even bias, we like to beat about the bush. A lot.

Sometimes this doesn't matter much. We're just sparing our future self from a guilty binge of word-eating, and everyone understands what we mean—no harm done. But there are occasions when a measure of unambiguous precision is called for. When we might want to be careful about the technical meanings of words like approximately, significant, and certain.

Sherman Kent was a CIA analyst in the Cold War, and he tasked himself with bringing quantitative rigour to the language of intelligence reports. He struggled (and eventually failed), meeting what he called aesthetic opposition:

What slowed me up in the first instance was the firm and reasoned resistance of some of my colleagues. Quite figuratively I am going to call them the poets—as opposed to the mathematicians—in my circle of associates, and if the term conveys a modicum of disapprobation on my part, that is what I want it to do. Their attitude toward the problem of communication seems to be fundamentally defeatist. They appear to believe the most a writer can achieve when working in a speculative area of human affairs is communication in only the broadest general sense. If he gets the wrong message across or no message at all—well, that is life.

Sherman Kent, Words of Estimative Probability, CIA Studies in Intelligence, Fall 1964

Kent proposed using some specific words to convey specific levels of certainty (right). We have used these words in our mobile app Risk*. The only modification I made was setting P = 0.99 for Certain, and P = 0.01 for Impossible (see my remark about proving things in geology).

There are other schemes. Most petroleum geologists know Peter Rose's work. A common language, with some quantitative meaning, can dull the pain of prospect risking sessions. Almost certainly. Probably.

Do you use systematic descriptions of uncertainty? Do you think they help? How can we balance our poetic side of geology with the mathematical?

Update on 2011-10-14 14:36 by Matt Hall

As I was adding to the SubSurfWiki page for WEPs, I came across a wonderful article by Bernie O'Brien (1989), a physician. He interviewed 56 doctors about twenty-three words and phrases, asking them to place them on a probability scale. He then used the interquartile range of the responses as an indication of ambiguity. Here's how his data plot:

This is very interesting: words used to express equivocality and fence-sitting are themselves ambiguous and uncertain. That makes intuitive sense, but it's a fascinating insight into the language of uncertainty.

O'Brien also compared the interquartile range to a 3-point rating of ambiguity, as given by the respondents. You can read more about it on the wiki page. 

Reference
O'Brien, B (1989), Words or numbers? The evaluation of probability expressions in general practice. Journal of the Royal College of General Practitioners 39, p 98–100, March 1989. Link to PDF.

Where on (Google) Earth #315

After a long break from this awesome game, I got WoGE #314 by simple recognition. I've never been to Florida, but have scoured the whole region looking for interesting modern analogs. So I have the honour of turning in the next edition; the time is 1100 ADT, 1400 GMT, or 44-07-07 ∇ 14:19:14 Lunar Standard Time. In case you're on the moon.

Where on (Google) Earth is the best way to tour the virtual globe since the mighty View-Master. If you are new to the game, fear not, it is easy to play. The winner is the first person to examine the picture below, find the location (name, link, or lat-long), and give a brief explanation of its geological interest. Please post your answer in the comments. And thanks to the Schott Rule, which I am invoking, newbies have a slight edge: previous winners must wait one earth hour for each win before playing—with a maximum of 48 (yes, some people are quite good at this game).

So: where and what the Dickens is this?

Update on 2011-10-15 19:32 by Matt Hall

It's been five days. Here's 100% more data, by way of a clue:

Update on 2011-10-17 12:50 by Matt Hall

This is off-topic; please refer to the comments to see why there is a picture of Paris here.

Image is ©Aerodata International Surveys, Digital Globe, GeoEye, IGN France, The GeoInformation Group. © Google

News of the week

Some news and views from the world of geoscience this last fortnight.

Open source GIS on a thumb drive

If you ever wanted to get into open source geospatial software but didn't know where to start, check this out. Last month OSGeo, the open source geospatial foundation, released version 5 of their OSGeo-Live project. This is a bootable disk image containing 47 pieces of free software, including several full GIS, world maps, and quick-start guides. Amazing!

Probability and panic

The L'Aquila earthquake of April 2009 killed 308 people. Six seismologists are now on trial for manslaughter, not so much because they failed to predict the quake, but because they allegedly downplayed the risk of a severe event. Most geoscientists believe that we cannot predict earthquakes today; these seismologists are effectively accused of trying to predict a non-earthquake. We don't know, but suspect their intent was misinterpreted—always a danger when specialists communicate with non-specialists. There is no daily coverage of the trial that we are aware of, but there are occasional reports in the press. In this short video, Giustino Parisse explains why he is one of the plaintiffs.

Magical geobloggery

If you're new to blogs—maybe you got a tablet recently and are discovering how easy it is to read the web these days—you might not be aware that there's a lot of geology in the blogosphere. Finding writers you want to read isn't easy though. You could scroll down this page and look for our BLOGROLL for some leads, or head over to Highly Allochthonous and read the latest Accretionary Wedge, a regular meta-post. This month: practical advice for the lifelong learner. 

Communicating rocks

We recently learned of this terrific new book from University of Houston professor Peter Copeland (thanks to his colleague, Rob Stewart, for the tip!). We haven't actually got our hands on it yet, but the Amazon preview has whet our appetites for geo-communication tips galore. The publisher, Prentice Hall, has kept the price to a reasonable amount, close to $35. Get your copy now!

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. Public domain map image from the USGS. 

Reuse and recycle

I have recently started teaching an undergraduate course at Dalhousie University in Halifax. The regular professor is on sabbatical, so this is a part-time gig, and a one-off. It's hard work, and shockingly poorly paid, but a lot of fun; I'm fortunate to have a fairly small group of bright, motivated students. 

One of the things that's surprised me is how little decent-quality and openly-licensed material there is on the internet for teaching technical courses like this. I can find images as well as the next person, and 'fair use' is acceptable for teaching I suppose, but often I'm left with a low-resolution image that doesn't quite show what I want. Thus I'm creating a lot of stuff from scratch, which is fine because I enjoy it, but it's time-consuming and, besides, I may never teach this course again.

So... I am uploading the drawings I make to SubSurfWiki.org, where you can find and download them, and use or abuse them for whatever you like without permission (they are all licensed CC-BY so you only have to give attribution). They are in Scalable Vector Graphics format, so you can edit them with a vector graphics tool like Inkscape or Adobe Illustrator. 

Note: There are some issues with displaying SVG files in some browsers. They sometimes look weird or even broken. You should be able to download the files and use them in a vector graphics tool without any trouble. The only other option is to use the Portable Network Graphics files instead, as I often upload those too; look for the same name, with a PNG extension. 

The cratering hypothesis

A few years ago, I was interpreting the Devonian of northern Alberta in a beautiful 3D seismic reflection survey. Because the target zone was rather shallow, we had acquired a dataset with a very high trace density: a lot of spatial samples. This gave us a lot of detail in timeslices, even if the vertical section views weren't particularly high resolution in these deeper, high velocity sediments of the shallow Givetian carbonate seas.

A circular feature caught my eye. Unfortunately I can't show it to you because the data are proprietary, but it was quite conspicuous and impossible to ignore: perfectly round, about 1.5 km across, and with a central mound a couple of hundred metres in diameter. I showed it to a few people and everyone said, 'yeah, impact crater'. Or maybe I just always heard 'impact crater'. 

I really wanted it to be an impact crater. Bias number 1. 

My first action was to re-read one of my favourite papers ever: Simon Stewart's 1999 paper on circular geological features. I love papers like this: basic, practical advice for interpreters. His figure 1 (left) is a lovely graphic. Stewart himself is rather enamoured with impact structures—he was the 'for' advocate in the recent debate over the Silverpit structure in the North Sea. You can read some more about it here and here. 

The paper gives some equations which compute the probability that, given some assumptions about meteorite flux and so forth, a bolide has cratered right where you are standing at some point in geological history. I built this little Wolfram|Alpha Widget so you can try them yourself (need help?). Of course, this is far from the same thing as there being a crater preserved, or visible in seismic, but it's a start. Bias number 2: Numbers, even dubious ones, look like evidence.

I admit it, I got carried away. Bias number 3.

But then... we shot another survey. There turned out to be another crater. And then another. My biases weren't enough—new craters finished it. According to those equations, the probability of having one in a 600 km² survey spanning 200 Ma of preservable time is 0.14, a 14% chance. Pretty good. But the probability of two is 0.012, and three is 0.0007. And these were contemporaneous. And, just as with Silverpit, there was salt. 

It should have been obvious all along. (Bias number 4.)

Reference
Stewart, S (1999). Seismic interpretation of circular geological structures. Petroleum Geoscience 5, p 273–285. DOI: 10.1144/petgeo.5.3.273

Image from Stewart 1999 is copyright of the Geological Society of London and the European Association of Geoscientists and Engineers, and is used here with permission and with thanks.

Learn to program

This is my contribution to the Accretionary Wedge geoblogfest, number 38: Back to School. You can read all about it, and see the full list of entries, over at Highly Allochthonous. To paraphrase Anne's call to words:

What do you think students should know? What should universities be doing better? What needs do you see for the rising generation of geoscientists? What skills and concepts are essential? How important are things like communication and quantitative skills versus specific knowledge about rocks/water/maps?

Learn to program

The first of doubtless many moments of envy of my kids' experience of childhood came about two years ago when my eldest daughter came home from school and said she'd been programming robots. Programming robots. In kindergarten. 

For the first time in my life, I wished I was five. 

Most people I meet and work with do not know how to make a computer do what they want. Instead, they are at the mercy of the world's programmers and—worse—their IT departments. The accident of the operating system you run, the preferences of those that came before you, and the size of your budget should not determine the analyses and visualizations you can perform on your data. When you read a paper about some interesting new method, imagine being able to pick up a keyboard and just try it, right now... or at least in an hour or two. This is how programmers think: when it comes to computers at least, their world is full of possibility, not bound by software's edges or hardwired defaults.

I want to be plain about this though: I am not suggesting that all scientists should become programmers, hacking out code, testing, debugging, and doing no science. But I am suggesting that all scientists should know how computer programs work, why they work, and how to tinker. Tinkering is an underrated skill. If you can tinker, you can play, you can model, you can prototype and, best of all, you can break things. Breaking things means learning, rebuilding, knowing, and creating. Yes: breaking things is creative.

But there's another advantage to learning to program a computer. Programming is a special kind of problem-solving, and rewards thought and ingenuity with the satisfaction of immediate and tangible results. Getting it right, even just slightly, is profoundly elating. To get these rewards more often, you break problems down, reducing them to soluble fragments. As you get into it, you appreciate the aesthetics of code creation: like equations, computer algorithms can be beautiful.

The good news for me and other non-programmers is that it's never been faster or simpler to give programming a try. There are even some amazing tools to teach children and other novices the concepts of algorithms and procedures; MIT's Scratch project is a leader in that field. Some teaching tools, like the Lego MINDSTORMS robotics systems my daughter uses, and App Inventor for Android (right), are even capable of building robust, semi-scientific applications. 

Chances are good that you don't even need to install anything to get started. If you have a Mac or a Linux machine then you already have instant access to scripting-cum-programming languages like the shell, AWK, Perl and Python. There's even a multi-language interpreter online at codepad.org. These languages are very good places to start: you can solve simple problems with them very quickly and, once you've absorbed the basics, you'll use them every day. Start on AWK now and you'll be done by lunchtime tomorrow. 

For what's it's worth, here are a few tips I'd give anyone learning to program:

• Don't do anything until you have a specific, not-too-hard problem to solve with a computer
• If you can't think of anything, the awesome Project Euler has hundreds of problems to solve
• Choose a high-level language like Python, Perl, or perhaps even Java; stay away from FORTRAN and C
• Buy no more than one single book, preferably a thick one with a friendly title from O'Reilly
• Don't do a course before you've tinkered on your own for a bit, but don't wait too long either (here's one)
• Learn to really use Google: it's the fastest way to figure out what you want to do
• Have fun brushing up on your math, especially trig, time series analysis, and inverse theory
• Share what you build: help others learn and get more open

Bust out of the shackles of other people's software: learn to program!

Update on 2011-10-02 00:38 by Matt Hall

If you have some programming or scripting skillz already, here's another codepad-like to look at. The nicely-designed repl.it can help you explore your multi-lingual side and try out a few languages you might have wondered about. Examples included. 

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.

Workshop? Talkshop

Day 4 of the SEG Annual Meeting. I attended the workshop entitled Geophysical data interpretation for unconventional reservoirs. It was really about the state of the art of seismic technologies for shale gas exploration and exploitation, but an emergent theme was the treatment of the earth as an engineering material, as opposed to an acoustic or elastic medium.

Harvey Goodman from Chevron started the workshop by asking the packed room, "are there any engineers in the room?" Hilariously, a single lonesome hand was raised. "Well," he said "this talk is for you." Perhaps this wasn't the venue for it; so much for spreading cross-disciplinary love and the geophysical technical vernacular. 

Mark Zoback from Stanford presented decades worth of laboratory measurements on the elastic/plastic properties of shales. Specifically the concentrations of illite and TOC on mechanical stiffness and creep. When it came to questions, he provided the most compentent and cogent responses of the day: every one was gold. Your go-to guy for shale geomechanics.

Marita Gading of Statoil presented some facinating technology called Source Rock from Seismic (we mentioned this on Monday)—a way to estimate total organic carbon from seismic for basin modeling and play evaluation. She listed the factors controling acoustic properties of shales as

1. organic content;
2. compaction or porosity;
3. lithotype and mineral composition;
4. seismic to microscale anisotropy.

She showed an empirically derived acoustic impedance transform coupled with more interpretive methods, and the results are compelling. It's not clear how well this might work in ancient shales onshore, but it has apparently worked for Statoil in younger, offshore basins.

Galen Treadgold from Global Geophysical gave a visually stunning presentation showing the value of expansive data sets in the Eagle Ford shale. He showed 1000 km² of 3D seismic that had been stitched together, highlighting the need to look at a regional picture. Patchwork data fails to give the same clarity of variation in mechanical stratigraphy.

The session shifted to the state of microseismic technology and 'getting beyond the dots'. Speakers from rival companies MicroSeismic, ESG Solutions, and Pinnacle described how microseismic waveforms are now being used to resolve moment tensors. These provide not only the location and magnitude but also the failure characteristic of every single event. While limited by uncertainty, they may be the way to get the industry beyond the prevailing bi-wing paradigm.

The session was a nice blend of disciplines, with ample time for question and answer. I struggle though to call it a workshop, it felt like a continuation of the huge number of talks that have been going on in the same room all week. Have you ever been to a stellar workshop? What made it great? 

More from our SEG 2011 experience.

Curvelets, dreamlets, and a few tears

Day 3 of the SEG Annual Meeting came and went in a bit of a blur. Delegates were palpably close to saturation, getting harder to impress. Most were no longer taking notes, happy to let the geophysical tide of acoustic signal, and occasional noise, wash over them. Here's what we saw.

Gilles Hennenfent, Chevron

I (Evan) loved Gilles's talk Interpretive noise attenuation in the curvelet domain. For someone who is merely a spectator in the arena of domain transforms and noise removal techniques, I was surprised to find it digestable and well-paced. Coherent noise can be difficult to remove independently from coherent signal, but using dyadic partitions of the frequency-wavenumber (f-k) domain, sectors called curvelets can be muted or amplified for reducing noise and increasing signal. Curvelets have popped up in a few talks, because they can be a very sparse representation of seismic data.

Speaking of exotic signal decompositions, Ru-Shan Wu, University of California at Santa Clara, took his audience to new heights, or depths, or widths, or... something. Halfway through his description of the seismic wavefield as a light-cone in 4D Fourier time-space best characterized by drumbeat beamlets—or dreamlets—we realized that we'd fallen through a wormhole in the seismic continuum and stopped taking notes.

Lev Vernik, Marathon

Lev dished a delicious spread of tidbits crucial for understanding the geomechanical control on hydraulic fracture stimulations. It's common practice to drill parallel to the minimum horizontal stress direction to optimize fracture growth away from the well location. For isotropic linear elastic fracture behaviour, the breakdown pressure of a formation is a function of the maximum horizontal stress, the vertical stress, the pore pressure, and the fracture toughness. Unfortunately, rocks we'd like to frack are not isotropic, and need to be understood in terms of anisotropy and inelastic strains.

Lastly, we stopped in to look at the posters. But instead of being the fun-fest of awesome geoscience we were looking forward to (we're optimistic people), it was a bit of a downer and made us rather sad. Posters are often a bit unsatisfactory for the presenter: they are difficult to make, and often tucked away in a seldom-visited corner of the conference. But there was no less-frequented corner of San Antonio, and possibly the state of Texas, than the dingy poster hall at SEG this year. There were perhaps 25 people looking at the 400-or-so posters. Like us, most of them were crying.

More posts from SEG 2011.