Lots of news!

I can't believe it's been a month since my last post! But I've now recovered from the craziness of the spring — with its two hackathons, two conferences, two new experiments, as well as the usual courses and client projects — and am ready to start getting back to normal. My goal with this post is to tell you all the exciting stuff that's happened in the last few weeks.

Meet our newest team member

There's a new Agilist! Robert Leckenby is a British–Swiss geologist with technology tendencies. Rob has a PhD in Dynamic characterisation and fluid flow modelling of fractured reservoirs, and has worked in various geoscience roles in large and small oil & gas companies. We're stoked to have him in the team!

Rob lives near Geneva, Switzerland, and speaks French and several other human languages, as well as Python and JavaScript. He'll be helping us develop and teach our famous Geocomputing course, among other things. Reach him at robert@agilescientific.com.


Geocomputing Summer School

We have trained over 120 geoscientists in Python so far this year, but most of our training is in private classes. We wanted to fix that, and offer the Geocomputing class back for anyone to take. Well, anyone in the Houston area :) It's called Summer School, it's happening the week of 13 August, and it's a 5-day crash course in scientific Python and the rudiments of machine learning. It's designed to get you a long way up the learning curve. Read more and enroll. 

A new kind of event

We have several more events happening this year, including hackathons in Norway and in the UK. But the event in Anaheim, right before the SEG Annual Meeting, is going to be a bit different. Instead of the usual Geophysics Hackathon, we're going to try a sprint around open source projects in geophysics. The event is called the Open Geophysics Sprint, and you can find out more here on events.agilescientific.com.

That site — events.agilescientific.com — is our new events portal, and our attempt to stay on top of the community events we are running. Soon, you'll be able to sign up for events on there too (right now, most of them are still handled through Eventbrite), but for now it's at least a place to see everything that's going on. Thanks to Diego for putting it together!

On principles and creativity

I recently heard a quote that resonated with me:


I grapple with this sentiment whenever I feel the selfish twinge of hesitation to donate money to Wikipedia or QGIS, or pay page fees for open access to an article, or otherwise cough up for my convictions.

Curious about who had uttered this wisdom, I looked it up. Turns out it was Bill Bernbach, celebrated advertiser, and supposedly an inspiration for the Don Draper character in Mad Men.


One of the founders of Doyle Dane Bernbach, now known as DDB, he brought bare-faced truth to the forefront in advertising, calling VW Beetles 'small', and proudly declaring Avis 'number 2'. He basically invented Apple's entire aesthetic in the late 50's , about four decades before Apple started to 'Think Different'.

He said some other true things. This could be about scientific communication:

The truth isn't the truth until people believe you, and they can't believe you if they don't know what you're saying, and they can't know what you're saying if they don't listen to you, and they won't listen to you if you're not interesting, and you won't be interesting unless you say things imaginatively, originally, freshly.

Now 'science' and 'truth' are not the same thing, so I don't want to try to claim that this sums things up perfectly, but I think the general point is important and we'll be better scientists if we live by it.

And I like this one too:


Too many organizations, and individuals, think their advantage must come from money, or secrecy, or patents, or other obvious, easily copied, things. But thinking about your creative edge first makes you take care of important things, and stop worrying about unimportant things.

I think this is an important idea, because creativity is, almost by definition, uncopyable. It feels like a slippery thing to build a company on or strategize about because while there's a limitless supply of the stuff, it's hard to maintain — and exploit. Creativity for its own sake is almost useless, but combined with a "Just ship it!" mentality, it's an unstoppable force.

The image of Bill Bernbach and the VW Beetle ad are both copyright of DDB Worldwide Communications Group and low-res images are used here in accordance with fair use rules. 

Finding Big Bertha with a hot wire


Sunday will be the 131st birthday of General Andrew McNaughton, a Canadian electrical engineer who served in the Canadian Expeditionary Force in the First World War. He was eventually appointed commander of the Canadian Corps Heavy Artillery and went on to serve in the Second World War as well.

So what is a professional soldier doing on a blog about geoscience? Well, McNaughton was part of the revolution of applied acoustics and geophysics that emerged right before and after the First World War.

Along with eminent British physicist Lawrence Bragg, engineer William Sansome Tucker, and physicist Charles Galton Darwin (the other Charles Darwin's grandson), among others, McNaughton applied physics to the big problem of finding the big noisy things that were trying to blow everyone up. They were involved in an arms race of their own — German surveyor Ludger Mintrop was trying to achieve the same goal from the other side of the trenches.


After gaining experience as a gunner, McNaughton became one of a handful of scientists and engineers involved in counter-battery operations. Using novel ranging techniques, these scientists gave the allied forces a substantial advantage over the enemy. Counter-battery fire became an weapon at pivotal battles like Vimy Ridge, and certainly helped expedite the end of the war.

If all this sounds like a marginal way to win a battle, stop think for a second about these artillery. The German howitzer, known as 'Big Bertha' (left), could toss an 820 kg (1800 lb) shell about 12.5 km (7.8 miles). In other words, it was incredibly annoying.

Combining technologies

Localization accuracy on the order of 5–10 m on the large majority of gun positions was eventually achieved by the coordinated use of several technologies, including espionage, cartography, aerial reconnaissance photography, and the new counter-measures of flash spotting and sound ranging.

Flash spotting was more or less just what it sounds like: teams of spotters recording the azimuth of artillery flashes, then triangulating artillery positions from multiple observations. The only real trick was in reporting the timing of flashes to help establish that the flashes came from the same gun.

Sound ranging, on the other hand, is a tad more complicated. It seems that Lawrence Bragg was the first to realize that the low frequency sound of artillery fire — which he said lifted him off the privy seat in the outhouse at his lodgings — might be a useful signal. However, microphones were not up to the task of detecting such low frequencies. Furthermore, the signal was masked by the (audible) sonic boom of the shell, as well as the shockwaves of passing shells.

Elsewhere in Belgium, William Tucker had another revelation. Lying inside a shack with holes in its walls, he realized that the 20 Hz pressure wave from the gun created tiny puffs of air through the holes. So he looked for a way to detect this pulse, and came up with a heated platinum wire in a rum jar. The filament's resistance dropped when cooled by the wavefront's arrival through an aperture. The wire was unaffected by the high-frequency shell wave. Later, moving-coil 'microphones' (geophones, essentially) were also used, as well as calibration for wind and temperature. The receivers were coupled with a 5-channel string galvanometer, invented by French engineers, to record traces onto 35-mm film bearing timing marks:


McNaughton continued to develop these technologies through the war, and by the end was successfully locating the large majority of enemy artillery locations, and was even able to specify the calibre of the guns and their probable intended targets. Erster Generalquartiermeister Erich Ludendorff commented at one point in the war: 

According to a captured English document the English have a well- developed system of sound-ranging which in theory corresponds to our own. Precautions are accordingly to be taken to camouflage the sound: e.g. registration when the wind is contrary, and when there is considerable artillery activity, many batteries firing at the same time, simultaneous firing from false positions, etc.

An acoustic arsenal


The hot-wire artillery detector was not Tucker's only acoustic innovation. He also pioneered the use of acoustic mirrors for aircraft detection. Several of these were built around the UK's east coast, starting around 1915 — the three shown here are at Denge in Kent. They were rendered obselete by the invention of radar around the beginning of World War Two.

Acoustic and seismic devices are still used today in military and security applications, though they are rarely mentioned in applied geophysics textbooks. If you know about any interesting contemporary uses, tell us about it in the comments.

According to Crown Copyright terms, the image of McNaughton is out of copyright. The acoustic mirror image is by Paul Russon, licensed CC-BY-SA. The uncredited/unlicensed galvanometer trace is from the excellent Stop, hey, what's that sound article on the geographical imaginations blog; I assume it is out of copyright. The howitzer image is out of copyright.

This post on Target acquisition and counter battery is very informative and has lots of technical details, though most of it pertains to later technology. The Boom! Sounding out the enemy article on ScienceNews for Students is also very nice, with lots of images. 

90 years of well logs

Today is the 90th anniversary of the first well log. On 5 September 1927, three men from Schlumberger logged the Diefenbach [sic] well 2905 at Dieffenbach-lès-Wœrth in the Pechelbronn heavy oil field in the Alsace region of France.

The site of the Diefenbach 2905 well. © Google, according to  terms .

The site of the Diefenbach 2905 well. © Google, according to terms.


The geophysical services company Société de Prospection Électrique (Processes Schlumberger), or PROS, had only formed in July 1926 but already had sixteen employees. Headquartered in Paris at 42, rue Saint-Dominique, the company was attempting to turn its resistivity technology to industrial applications, especially mining and petroleum. Having had success with horizontal surface measurements, the Diefenbach well was the first attempt to measure resistivity in a wellbore. PROS went on to become Schlumberger.

The resistivity prospecting system had been designed by the Schlumberger brothers, Conrad (1878–1936, a professor at École des Mines) and Maurice (1884–1953, a mining engineer), over the period from about 1912 until 1923. The task of adapting the technology was given to Henri Doll (1902–1991), Conrad's son-in-law since 1923, and the Alsatian well was to be the first field test of the so-called "electrical coring" method. The client was Deutsche Erdöl Aktiengesellschaft, now DEA of Hamburg, Germany.

As far as I can tell, the well — despite usually being called "the Pechelbronn well" — was located at the site of a monument at the intersection of Route de Wœrth with Rue de Preuschdorf in Dieffenbach-lès-Wœrth, about 3 km west of Merkwiller-Pechelbronn. Henri Doll logged the well with Roger Jost and Charles Scheibli. Using rudimentary equipment, they logged about 145 m of the 488-metre hole, starting at 279 m MD, taking a reading every metre and plotting the log by hand. Yesterday I digitized this log; download it in LAS format here


The story of what the Schlumberger brothers and Henri Doll achieved is fascinating; I recommend reading Don Hill's brief history (2012) — it's free to read at Wiley. The period of invention that followed the Pechelbronn success was inspiring.

If you're looking at well logs today, take a second to thank Conrad, Maurice, and Henri for their remarkable idea.

PS If you're interested in petroleum history, the AOGHS page This Week is worth a look.

The French television programme Midi en France recorded this segment about the Pechelbronn field in 2014. The narration is in French, "The fields of maize gorge on sunshine, the pumps on petroleum...", but there are some nice pictures to look at.

References and bibliography

Clapp, Frederick G (1932). Oil and gas possibilities of France. AAPG Bulletin 16 (11), 1092–1143. Contains a good history of exploration and production from the Oligocene sands in Pechelbronn, up to about 1931 (the field produced up to 1970). AAPG Datapages.

Delacour, Jacques (2003). Une technique de prospection minière et pétrolière née en Pays d'Auge. SABIX 34, September 2003. Available online.

École des Mines page on Conrad Schlumberger at annales.org.

Hill, DG (2012). Appendix A: Historical Review (Milestone Developments in Petrophysics). In: Buryakovsky, L, Chilingar, GV, Rieke, HH, and Shin, S (2012). Petrophysics: Fundamentals of the Petrophysics of Oil and Gas Reservoirs, John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9781118472750.app1. A nice potted history of well logging, including important dates.

Musée Français du Pétrole website, http://www.musee-du-petrole.com/historique/

Pike, B and Duey, R (2002). Logging history rich with innovation. Hart's E&P Magazine. September 2002. Available online. Interesting article, but beware: there are one or two inaccuracies in this article, and I believe the image of the well log is incorrect.

Poisson's controversial stretch-squeeze ratio

Before reading this, you might want to check out the previous post about Siméon Denis Poisson's life and career. Then come back here...

Physicists and mathematicians knew about Poisson's ratio well before Poisson got involved with it. Thomas Young described it in his 1807 Lectures on Natural Philosophy and the Mechanical Arts:

We may easily observe that if we compress a piece of elastic gum in any direction, it extends itself in other directions: if we extend it in length, its breadth and thickness are diminished.

Young didn't venture into a rigorous formal definition, and it was referred to simply as the 'stretch-squeeze ratio'.

A new elastic constant?

Twenty years later, at a time when France's scientific muscle was fading along with the reign of Napoleon, Poisson published a paper attempting to restore his slightly bruised (by his standards) reputation in the mechanics of physical materials. In it, he stated that for a solid composed of molecules tightly held together by central forces on a crystalline lattice, the stretch squeeze ratio should equal 1/2 (which is equivalent to what we now call a Poisson's ratio of 1/4). In other words, Poisson regarded the stretch-squeeze ratio as a physical constant: the same value for all solids, claiming, 'This result agrees perfectly' with an experiment that one of his colleagues, Charles Cagniard de la Tour, recently performed on brass. 

Poisson's whole-hearted subscription to the corpuscular school certainly prejudiced his work. But the notion of discovering of a new physical constant, like Newton did for gravity, or Einstein would eventually do for light, must have been a powerful driving force. A would-be singular elastic constant could unify calculations for materials soft or stiff — in contrast to elastic moduli which vary over several orders of magnitude. 

Poisson's (silly) ratio

Later, between 1850 and 1870, the physics community acquired more evidence that the stretch-squeeze ratio was different for different materials, as other materials were deformed with more reliable measurements. Worse still, de la Tour's experiments on the elasticity of brass, upon which Poisson had hung his hat, turned out to be flawed. The stretch-squeeze ratio became known as Poisson's ratio not as a tribute to Poisson, but as a way of labeling a flawed theory. Indeed, the falsehood became so apparent that it drove the scientific community towards treating elastic materials as continuous media, as opposed to an ensemble of particles.

Today we define Poisson's ratio in terms of strain (deformation), or Lamé's parameters, or the speed \(V\) of P- and S-waves:


Interestingly, if Poisson turned out to be correct, and Poisson's ratio was in fact a constant, that would mean that the number of elastic constants it would take to describe an isotropic material would be one instead of two. It wasn't until Augustin Louis Cauchy used the notion of a stress tensor to describe the state of stress at a point within a material, with its three normal stresses and three shear stresses, did the need for two elastic constants become apparent. Tensors gave the mathematical framework to define Hooke's law in three dimensions. Found in the opening chapter in any modern textbook on seismology or mechanical engineering, continuum mechanics represents a unique advancement in science set out to undo Poisson's famously false deductions backed by insufficient data.


Greaves, N (2013). Poisson's ratio over two centuries: challenging hypothesis. Notes & Records of the Royal Society 67, 37-58. DOI: 10.1098/rsnr.2012.0021

Editorial (2011). Poisson's ratio at 200, Nature Materials10 (11) Available online.


Great geophysicists #13: Poisson

Siméon Denis Poisson was born in Pithiviers, France, on 21 June 1781. While still a teenager, Poisson entered the prestigious École Polytechnique in Paris, and published his first papers in 1800. He was immediately befriended — or adopted, really — by Lagrange and Laplace. So it's safe to say that he got off to a pretty good start as a mathematician. The meteoric trajectory continued throughout his career, as Poisson received more or less every honour a French scientist could accumulate. Along with Laplace and Lagrange — as well as Fresnel, Coulomb, Lamé, and Fourier — his is one of the 72 names on the Eiffel Tower.

Wrong Poisson

In the first few decades following the French Revolution, which ended in 1799, France enjoyed a golden age of science. The Société d’Acrueil was a regular meeting of savants, hosted by Laplace and the chemist Claude Louis Berthollet, and dedicated to the exposition of physical phenomena. The group worked on problems like the behaviour of gases, the physics of sound and light, and the mechanics of deformable materials. Using Newton's then 120-year-old law of gravitation as an analogy, the prevailing school of thought accounted for all physical phenomena in terms of forces acting between particles. 

Poisson was not flawless. As one of the members of this intellectual inner circle, Poisson was devoted to the corpuscular theory of light. Indeed, he dismissed the wave theory of light completely, until proven wrong by Thomas Young and, most conspicuously, Augustin-Jean Fresnel. Even Poisson's ratio, the eponymous elastic modulus, wasn't the result of his dogged search for truth, but instead represents a controversy that drove the development of the three-dimensional theory of elasticity. More on this next time.

The workaholic

Although he did make time for his wife and four children — but only after 6 pm — Poisson apparently had little time for much besides mathematics. His catchphrase was

Life is only good for two things: doing mathematics and teaching it.

In the summer of 1838, he learned he had a form of tuberculosis. According to James (2002), he was unable to take time away from work for long enough to recuperate. Eventually, insisting on conducting the final exams at the Polytechnique for the 23rd year in a row, he took on more than he could handle. He died on 20 April 1840. 


Grattan-Guinness, I. (1990). Convolutions in French Mathematics, 1800-1840: From the Calculus and Mechanics to Mathematical Analysis and Mathematical Physics. Vol.1: The Setting. Springer Science & Business Media. 549 pages.

Ioan James, I (2002). Remarkable Mathematicians: From Euler to Von Neumann. Cambridge University Press, 433 pages.

The University of St Andrews MacTutor archive article on Poisson.

Great geophysicists #12: Gauss

Carl Friedrich Gauss was born on 30 April 1777 in Braunschweig (Brunswick), and died at the age of 77 on 23 February 1855 in Göttingen. He was a mathematician, you've probably heard of him; he even has his own Linnean handle: Princeps mathematicorum, or Prince of mathematicians (I assume it's the royal kind, not the Purple Rain kind — ba dum tss).

Gauss's parents were poor, working class folk. I wonder what they made of their child prodigy, who allegedly once stunned his teachers by summing the integers up to 100 in seconds? At about 16, he was quite a clever-clogs, rediscovering Bode's law, the binomial theorem, and the prime number theorem. Ridiculous.

His only imperfection was that he was too much of a perfectionist. His motto was pauca sed matura, meaning "few, but ripe". It's understandable how someone so bright might not feel much need to share his work, but historian Eric Temple Bell reckoned that if Gauss had published his work regularly, he would have advanced mathematics by fifty years.

He was only 6 when Euler died, but surely knew his work. Euler is the only other person who made comparably broad contributions to what we now call the exploration geophysics toolbox, and applied physics in general. Here are a few: 

  • He proved the fundamental theorems of algebra and arithmetic. No big deal.
  • He formulated the Gaussian function — which of course crops up everywhere, especially in geostatistics. The Ricker wavelet is a pulse with frequencies distributed in a Gaussian.
  • The gauss is the cgs unit of magnetic flux density, thanks to his work on the flux theorem, one of Maxwell's equations.
  • He discovered the Cauchy integral theorem for contour integrals but did not publish it.
  • The 'second' or 'total' curvature — a coordinate-system-independent measure of spatial curvedness — is named after him.
  • He made discoveries in non-Euclidean geometry, but did not publish them.

Excitingly, Gauss is the first great geophysicist we've covered in this series to have been photographed (right). Unfortunately, he was already dead. But what an amazing thing, to peer back through time almost 160 years.

Next time: Augustin-Jean Fresnel, a pioneer of wave theory.

At home with Leonardo

Well, OK, Leonardo da Vinci wasn't actually there, having been dead 495 years, but on Tuesday morning I visited the house at which he spent the last three years of his life. I say house, it's more of a mansion — the Château du Clos Lucé is a large 15th century manoir near the centre of the small market town of Amboise in the Loire valley of northern France. The town was once the royal seat of France, and the medieval grandeur still shows. 

Leonardo was invited to France by King Francis I in 1516. Da Vinci had already served the French governor of Milan, and was feeling squeezed from Rome by upstarts Rafael and Michelangelo. It's nice to imagine that Frank appreciated Leo's intellect and creativity — he sort of collected artists and writers — but let's face it, it was probably the Italian's remarkable capacity for dreaming up war machines, a skill he had honed in the service of mercenary and cardinal Cesare Borgia. Leonardo especially seemed to like guns; here are models of a machine gun and a tank, alongside more peaceful concoctions:

Inspired by José Carcione's assertion that Leonardo was a geophysicst, and plenty of references to fossils (even Palaeodictyon) in his notebooks, I scoured the place for signs of Leonardo dablling in geology or geophysics, but to no avail. The partly-restored Renaissance floor tiles did have some inspiring textures and lots of crinoid fossils... I wonder if he noticed them as he shuffled around?

If you are ever in the area, I strongly recommend a visit. Even my kids (10, 6, and 4) enjoyed it, and it's close to some other worthy spots., specifically Chenonceau (for anyone) and Cheverny (for Tintin fans like me). The house, the numerous models, and the garden (below — complete with tasteful reproductions from Leonardo's works) were all terrific.

Check out José Carcione's two chapters about Leonardo and
his work in 52 Things You Should Know About Geophysics.
Download the chapter for free! [PDF, 3.8MB]

Great geophysicists #11: Thomas Young

Painting of Young by Sir Thomas LawrenceThomas Young was a British scientist, one of the great polymaths of the early 19th century, and one of the greatest scientists. One author has called him 'the last man who knew everything'¹. He was born in Somerset, England, on 13 June 1773, and died in London on 10 May 1829, at the age of only 55. 

Like his contemporary Joseph Fourier, Young was an early Egyptologist. With Jean-François Champollion he is credited with deciphering the Rosetta Stone, a famous lump of granodiorite. This is not very surprising considering that at the age of 14, Young knew Greek, Latin, French, Italian, Hebrew, Chaldean, Syriac, Samaritan, Arabic, Persian, Turkish and Amharic. And English, presumably. 

But we don't include Young in our list because of hieroglyphics. Nor  because he proved, by demonstrating diffraction and interference, that light is a wave — and a transverse wave at that. Nor because he wasn't a demented sociopath like Newton. No, he's here because of his modulus

Elasticity is the most fundamental principle of material science. First explored by Hooke, but largely ignored by the mathematically inclined French theorists of the day, Young took the next important steps in this more practical domain. Using an empirical approach, he discovered that when a body is put under pressure, the amount of deformation it experiences is proportional to a constant for that particular material — what we now call Young's modulus, or E:

This well-known quantity is one of the stars of the new geophysical pursuit of predicting brittleness from seismic data, and a renewed interested in geomechanics in general. We know that Young's modulus on its own is not enough information, because the mechanics of failure (as opposed to deformation) are highly nonlinear, but Young's disciplined approach to scientific understanding is the best model for figuring it out. 

Sources and bibliography


¹ Thomas Young wrote a lot of entries in the 1818 edition of Encyclopædia Britannica, including pieces on bridges, colour, double refraction, Egypt, friction, hieroglyphics, hydraulics, languages, ships, sound, tides, and waves. Considering that lots of Wikipedia is from the out-of-copyright Encyclopædia Britannica 11th ed. (1911), I wonder if some of Wikipedia was written by the great polymath? I hope so.

April linkfest

It's time for our regular linkfest!

There's a new book in town... Rob Simm and Mike Bacon have put together a great-looking text on seismic amplitude intepretation (Cambridge, 2014). Mine hasn't arrived yet, so I can't say much more — for now, you can preview it in Google Books. I should add it to my list.

Staying with new literature, I started editing a new column in SEG's magazine The Leading Edge in February. I wrote about the first instalment, and now the second is out, courtesy of Leo Uieda — check out his tutorial on Euler deconvolution, complete with code. Next up is Evan with a look at synthetics.

On a related note, Matteo Niccoli just put up a great blog post on his awesome perceptual colourmaps, showing how to port them to matplotlib, the MATLAB-like plotting environment lots of people use with the Python programming language. 

Dolf Seilacher, the German ichnologist and palaeontologist, died 4 days ago at the age of 89. For me at least, his name is associated with the mysterious trace fossil Palaeodictyon — easily one of the weirdest things on earth (right). 

Geoscience mysteries just got a little easier to solve. As I mentioned the other day, there's a new place on the Internet for geoscientists to ask questions and help each other out. Stack Exchange, the epic Q&A site, has a new Earth Science site — check out this tricky question about hydrocarbon generation.

And finally, who would have thought that waiting 13 years for a drop of bitumen could be an anticlimax? But in the end, the long (if not eagerly) awaited 9th drop in the University of Queensland's epic experiment just didn't have far enough to fall...

If you can't get enough of this, you can wait for the 10th drop here. Or check back here in 2027.