October linkfest

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From Hart (2013). ©SEG/AAPGIt's the Hallowe'en linkfest! Just the good bits from our radar...

If you're a member of SEG or AAPG, you can't have missed their new joint-venture journal, Interpretation. Issue 2 just came out. My favourite article so far has been Bruce Hart's Whither seismic stratigraphy in Issue 1. It included these excellent little forward models from an earlier paper of his — it's so important for interpreter's to think in this space where geological architecture and geophysical imaging overlap. 

Muon tomography is in the news again, this time in relation to monitoring CCS repositories (last time it was volcanos). Jon Gluyas, author of the textbook Petroleum Geoscience, is the investgator at Durham in the UK (my alma mater). I do love the concept — imaging the subsurface with cosmic rays — but I'm only just getting to grips with sound waves.

If you read this blog regularly, you probably have some geeky tendencies. We've linked to a couple of these blogs before, but they're must-read for anyone into technology and geoscience, with lots of code and workflow examples: 

Continuing the geeky theme, we've been getting more and more into building things recently. Check out our fiddling in GitHub (a code repository) — an easy way in is code.agilegeoscience.com. Watch this space!

Speaking of fiddling with code, you already know about the hackathon we hosted in Houston last month. But there's talk of repeating the fun at the AAPG Annual Convention, also in Houston, in April next year. Brian Romans has started a list of potential projects around digital stratigraphy — please leave a comment there or here to add to it. Where's the gap in your workflow?

A few more quick hits:

If you want these nuggets fresh, you can follow me on Twitter or glance at my pinboard. If you have stuff to share, use the comments or get in touch. Over and out.

Seismic models: Hart, BS (2013). Whither seismic stratigraphy? Interpretation, volume 1 (1), and is copyright of SEG and AAPG. The image from the Trowel Blazers event is licensed CC-BY-SA by Wikipedia user Mrjohncummings. 

What is brittleness?

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Brittleness is an important rock characteristic, but impossible to define formally because there are so many different ways of looking at it. For this reason, Tiryaki (2006) suggests we call it a rock behaviour, not a rock property.

Indeed, we're not really interested in brittleness, per se, because it's not very practical information on its own. Mining engineers are concerned with a property called cuttability — and we can think of this as conceptually analogous to the property that interests lots of geologsts, geophysicists, and engineers in petroleum, geothermal, and hydrology: frackability. In materials science, the inverse property — the ability of a rock to resist fracture — is called fracture toughness. 

What is brittleness not?

  • It's not the same as frackability, or other things you might be interested in.
  • It's not a simple rock property like, say, density or velocity. Those properties are condition-dependent too, but we agree on how to measure them.
  • It's not proportional to any elastic moduli, or a linear combination of Young's modulus and Poisson's ratio, despite what you might have heard.

So what is it then?

It depends a bit what you care about. How the rock deforms under stress? How much energy it takes to break it? What happens when it breaks? Hucka and Das (1974) rounded up lots of ways of looking at it. Here are a few:

  • Brittle rocks undergo little to no permanent deformation before failure and, depending on the test conditions, may occur suddenly and catastrophically.
  • Brittle rocks undergo little or no ductile deformation past the yield point (or elastic limit) of the rock. Note that some materials, including many rocks, have no well-defined yield point because they have non-linear elasticity.
  • Brittle rocks absorb relatively little energy before fracturing. The energy absorbed is equal to the area under the stress-strain curve (see figure).
  • Brittle rocks have a strong tendency to fracture under stress.
  • Brittle rocks break with a high ratio of fine to coarse fragments.

All of this is only made more complicated by the fact that there are lots of kinds of stress: compression, tension, shear, torsion, bending, and impact... and all of these can operate in multiple dimensions, and on multiple time scales. Suddenly a uniaxial rig doesn't quite seem like enough kit.

It will take a few posts to really get at brittleness and frackability. In future posts we'll look at relevant rock properties and how to measure them, the difference between static and dynamic measurements, and the multitude of brittleness indices. Eventually, we'll get on to what all this means for seismic waves, and ask whether frackability is something we can reasonably estimate from seismic data.

Meanwhile, if you have observations or questions to share, hit us in the comments. 

References and further reading
Hucka V, B Das (1974). Brittleness determination of rocks by different methods. Int J Rock Mech Min Sci Geomech Abstr 10 (11), 389–92. DOI:10.1016/0148-9062(74)91109-7
Tiryaki (2006). Evaluation of the indirect measures of rock brittleness and fracture toughness in rock cutting. The Journal of The South African Institute of Mining and Metallurgy 106, June 2006. Available online.

P is for Phase

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Seismic is about acoustic vibration. The archetypal oscillation, the sine wave, describes the displacement y of a point around a circle. You only need three pieces of information to describe it perfectly: the size of the circle, the speed at which it rotates around the circle, and where it starts from expressed as an angle. These quantities are better known as the amplitude, frequency, and phase respectively. These figures show how varying each of them affects the waveform:

So phase describes the starting point as an angle, but notice that this manifests itself as an apparent lateral shift in the waveform. For seismic data, this means a time shift. More on this later. 

What about seismic?

We know seismic signals are not so simple — they are not repetitive oscillations — so why do the words amplitude, frequency and phase show up so often? Aren't these words horribly inadequate?

Not exactly. Fourier's methods allow us to construct (and deconstruct) more complicated signals by adding up a series of sine waves, as long as we get the amplitude, frequency and phase values right for each one of them. The tricky part, and where much of where the confusion lies, is that even though you can place your finger on any point along a seismic trace and read off a value for amplitude, you can't do that for frequency or phase. The information for those are only unlocked through spectroscopy.

Phase shifts or time shifts?

The Ricker wavelet is popular because it can easily be written analytically, and it is comprised of a considerable number of sinusoids of varying amplitudes and frequencies. We might refer to a '20 Hz Ricker wavelet' but really it contains a range of frequencies. The blue curve shows the wavelet with phase = 0°, the purple curve shows the wavelet with a phase shift of π/3 = 60° (across all frequencies). Notice how the frequency content remains unchanged.

So for a seismic reflection event (below), phase takes on a new meaning. It expresses a time offset between the reflection and the maximum value on the waveform. When the amplitude maximum is centered at the reflecting point, it is equally shaped on either side — we call this zero phase. Notice how variations in the phase of the event alter the relative position of the peak and sidelobes. The maximum amplitude of the event at 90° is only about 80% of the amplitude at zero phase. This is why I like to plot traces along with their envelope (the grey lines). The envelope contains all possible phase rotations. Any event whose maximum value does not align with the maximum on the envelope is not zero phase.

Understanding the role of phase in time series analysis is crucial for both data processors aiming to create reliable data, and interpreters who operate under the assertion that subtle variations in waveform shape can be attributed to underlying geology. Waveform classification is a powerful attribute... but how reliable is it?

In a future post, I will cover the concept of instantaneous phase on maps and sections, and some other practical interpretation tips. If you have any of your own, share them in the comments.

Additional reading
Liner, C (2002). Phase, phase, phase. The Leading Edge 21, p 456–7. Abstract online.

Do something that scares you

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Last week, I asked if we — our community of practice — is comfortable with the murky zone between corporate marketing and our technical societies. Lots of discussion ensued. On reflection, I was a little unclear about exactly whom I was picking on — corporate marketers (mostly) or technical societies. Today, I thought I'd dig deeper into the corporate marketing side a little, and think about what the future might look like. We can look at societies some other time. 

What marketing used to be

Marketing used to mean nothing less prosaic than buying and selling stuff. Since the post-war consumer revolution, it has gradually expanded in scope and today covers advertising, promotion, publicity, branding, and customer management.

Unfortunately, much of what comes out of marketing departments is spin. How else could it be? The marketers only have control over their own domain, they don't design or build or even use the products. They're 'only doing their job' — positioning their products in the market, obsessing about the competition, negotiating ad space, and tweaking their brand image. Beyond the simple transmission of information — a necessary service to the world — all this effort is aimed at making their products and services look better than they actually are. 

Recognizing brokenness

Some totally real readers of this blog. Let's start with some easy things: if your marketing people can't answer questions about your products and services, they don't care enough — replace them. If they write copy that contains the words 'innovative', 'breakthrough', or 'unleash' — replace them. If you ask them for 'something new' and get back stock photos with pictures of your software pasted over them — replace them.

The problem with all this — buying more ad space, building bigger booths, getting better seats at hockey games, and so on — is... well, there are lots:

  • We've seen it all before, it's boring. Is that your message?
  • Thanks to the Matthew effect, the biggest wallet will win. Is that you?
  • It's all about you, the brand, not them, your users and customers.
  • I don't trust you. You are biased. I trust my friends and colleagues. 

Walk the walk

Like losing weight, getting fit, or writing a novel, I'm afraid there's no easy way: you have to do the hard work. Stop looking for new ways to tell everyone you're the most awesome company with the most powerful software. Just be the most awesome company. Show don't tell. Build great software and services and, more importantly, do great things with them. Competitors can copy what you do, especially if they are Petrel (they will beat you every time), but not how you do it. Instead of trying to play tennis against Roger Federer, you might do better changing the game to The Settlers of Catan, or super-solar space spag (no, that game has not been invented yet). 

Here are some ideas for your next expo. These things should scare you. If not, find something that does.

  • Bring developers to talk to people and connect them with your users.
  • Show people your development process, your bug list, and your roadmap. 
  • Hold a clinic and help your users help each other do more awesome things.
  • Brainstorm new product ideas right there on the show floor. Have a developer prototype the best one each day.
  • Broadcast your ideas in front of your competitors. They will weep with fear because they know they lack your courage and audacity. They can copy algorithms, but they can't copy awesomeness. 
  • Watch people using your products. Let them teach you how they want to work.
  • Hold a contest to find The Power User. Can your best user beat your best consultant?
  • An iPad draw? Seriously? You just want my email address to spam me. I have an iPad.
  • Hide your sales and marketing people for a day and see what happens.

Above all, stop copying your competitors. They suck at marketing too. 

Advice for the rest of us

I know not everyone feels as strongly as I do, and some people seem happy with the status quo. But to everyone else, I have a challenge: Demand to be delighted.

Next time you are confronted with some sales and marketing cruft, dare to ask hard questions. Have high expectations. Refuse the stuffed toy — "What has this got to do with my work?". Laugh at the lame pen, don't stuff it in your pocket. Call out the sexist nonsense. And when you find a booth that's working hard to please the people that really matter, reward them with your attention.

If you're a marketer, what would you do if there was no risk of failure? If you're a victim of marketing, what would could should a service company do to delight you? 

Scientists not prospects

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If you've never worked on 'the dark side' — selling technical products and services — you may not think much about marketing. If you work for an energy company, and especially if you're a 'decision maker' (wait, don't we all make decisions?), you may not realize that it's all aimed at you. Every ad, every sponsored beer, every trade show booth and its cute bunnies. The marketers are the explorers, and you are the prospect.

My question is: are you OK with their exploration methods?

The cost of advertising

Marketing futurists have been saying for ages that interruption advertising is dead. Uncurated, highest-bidder, information-free ads, 'inserted' (that's what they call it) into otherwise interesting and useful 'content' do not work. Or at least, people can't agree on whether they work or not. And that means they don't. 

The price of print advertising does not reflect this, however. Quite the opposite. Here's what a year of premium full-page ads will cost you in three leading publications: 

Still not bad compared to Wired ($1.67 million). You start to understand why companies hire marketing people. Negotiating volume pricing and favourable placements is a big deal, think of the money you can save. What a shame ads bring nothing at all to our community. All that money — so little impact. Well, zero impact. 

Conferences are where it really gets serious. Everything has a price. Want to buy 250 gallons of filtrate, I mean 'sponsor a coffee break'? That will be $5000 but don't worry, you get a little folded card with your name on it (and some coffee stains). How about a booth in the exhibition? They are only $23 per sq ft (about $250/m2), so that big shiny booth? That'll be about $75,000. That's before you bring in carpet, drywall, theatrical lighting, displays, and an espresso machine.

No wonder one service company executive once told me: "It's not a waste of money. It's a colossal waste of money." He said they only went because people would talk if they didn't.

Welcome to the oil industry

Walking around the trade show at SEG the other week, we were not very surprised to be accosted by a troop of young women dressed in identical short, tight dresses, offering beer tickets. Where's the beer? At their booth, obviously, about half a kilometre away (Manhattan distance). Apparently the marketing department assumed that no-one in their right mind would visit their booth on the basis of their compelling products or their essential relationships with an engaged and enthusiastic user community. Come to think of it, they were probably correct.

One innovative company has invented time travel, but unfortunately only to 1975. At least, that's the easiest way to explain the shoeshine stand at Ovation's booth. You can imagine the marketing meeting: "Let's get some women in short skirts, and get them to shine people's shoes!" I expect someone said, "Wait, isn't this a technical conference for subsurface scientists, shouldn't we base our marketing strategy on delighting the industry with our unbeatable services?" — and after a moment's reflection, the raucous laughter confirming that yes, the sexy shoeshine stand was indeed an awesome idea.

Let's be clear: marketing, as practised in this industry, is a waste of money. And this latter kind of marketing — remarkable for all the wrong reasons — is an insult to our profession and our purpose. 

Are we cool with this?

Last year I asked whether we (our community of technical practitioners and scientists) are okay with burning 210 person-years of productivity at a major conference and having very little to show for it at the end. 

Today I'm asking a different question: are we okay with burning millions of dollars on glossy ads, carpeted booths, nasty coffee, and shoeshine stands? Is this an acceptable price for our attention? Is the signal:noise ratio high enough?

I am not sure where I'm going with all of this — I am still trying to figure out what I think about it all. But I know one thing: I can't stand it. I will not step into another exhibition. I am withdrawing my attention — which I suppose means that yours is now worth a tiny bit more. Or less.

Update on 2013-10-16 17:10 by Matt Hall

Anyone involved in marketing that has actuallyl read this far without surfing off in disgust might like to carry on reading the follow-up to this post — Do something that scares you.

Great geophysicists #9: Ernst Chladni

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Ernst Chladni was born in Wittenberg, eastern Germany, on 30 November 1756, and died 3 April 1827, at the age of 70, in the Prussian city of Breslau (now Wrocław, Poland). Several of his ancestors were learned theologians, but his father was a lawyer and his mother and stepmother from lawyerly families. So young Ernst did well to break away into a sound profession, ho ho, making substantial advances in acoustic physics. 

Chladni, 'the father of acoustics', conducted a large number of experiments with sound, measuring the speed of sound in various solids, and — more adventurously — in several gases too, including oxygen, nitrogen, and carbon dioxode. Interestingly, though I can find only one reference to it, he found that the speed of sound in Pinus sylvestris was 25% faster along the grain, compared to across it — is this the first observation of acoustic anisotropy? 

The experiments Chladni is known for, however, are the plates. He effectively extended the 1D explorations of Euler and Bernoulli in rods, and d'Alembert in strings, to the 2D realm. You won't find a better introduction to Chladni patterns than this wonderful blog post by Greg Gbur. Do read it — he segués nicely into quantum mechanics and optics, firmly linking Chladni with the modern era. To see the patterns forming for yourself, here's a terrific demonstration (very loud!)...

The drawings from Chladni's book Die Akustik are almost as mesmerizing as the video. Indeed, Chladni toured most of mainland Europe, demonstrating the figures live to curious Enlightenment audiences. When I look at them, I can't help wondering if there is some application for exploration geophysics — perhaps we are missing something important in the wavefield when we sample with regular acquisition grids?

References

Chladni, E, Die Akustik, Breitkopf und Härtel, Leipzig, 1830. Amazingly, this publishing company still exists.

Read more about Chladni in Wikipedia and in monoskop.org — an amazing repository of information on the arts and sciences. 

This post is part of a not-very-regular series of posts on important contributors to geophysics. It's going rather slowly — we're still in the eighteenth century. See all of them, and do make suggestions if we're missing some!

What we built at the weekend

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10 days ago we wrapped up the Geophysics Hackathon in Houston. I wrote a bit about it right after the event, but now I've gathered the evidence and can share more of the awesome. First of all — what did everyone build in the 2 days? 

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Team 1: Velocity modelling in iOS

Essau Worthy-Blackwell (Southwestern Energy), Jacob Foshee (independent iOS dev), Evan Bianco (Agile), and Ben Bougher (independent, mostly helping Agile) built 2 tools exploring velocity modelling and depth conversion. One was a desktop tool (in Python), the other was an iOS app — watch this.

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Team 2: LAS soup demux

Joe Jennings (Colorado School of Mines), Mike Stone (Lukoil), and Karl Schleicher (University of Texas at Austin) built a tool in Python for coping with messy data. Karl is a champion of open data, and needs a tool for quickly exploring large repositories. You can see their progress in the code in GitHub — feel free to help them out!

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Team 3: A 1D forward model

Duncan Child (Spectraseis) joined Chris Chalcraft, Paul Garossino, and James Alison from OpenGeoSolutions to help out with his pumped up Java and JSON wrangling skills. Greg Partyka even popped in to help. Here is Blockfilter in GitHub.

Everyone's a winner

As well as being a fun way to get to know people, and create something new together, the event was a (very low key) contest. We had some experienced and perceptive judges to pick some winners and decide how the exactly 3 prizes would be distributed among the exactly 3 teams:

  • Team 3 were awarded with some Raspberry Pi starter kits, to recognize their solid idea, well-constructed code, and respect for work-life balance (hey, it was the weekend!). It was fun peeking over their shoulders occasionally.

  • Team 2 had the most commercially viable product, and as such went away with 2 books: The Lean Startup by Eric Ries, and Business Model Generation by Alex Osterwalder. Thanks to sponsor SURGE Accelerator, the team also won the chance to talk to a business mentor about their ideas.

  • Team 1 delivered the shiniest product at the end of the weekend, with the iOS app and a desktop clone. They each won one of Google's latest Nexus 7 tablets, to continue with their app-building skills.

What will you build?

Thanks again to the daredevils who showed up, the judges — especially Maitri Erwin, who helped out in lots of ways all weekend — and of course the sponsors: OpenGeoSolutions, Enthought, and dGB Earth Sciences. If you missed the event, dear reader, I hope you'll come along next time to share ideas, test workflows, and build new things.