October linkfest

The linkfest has come early this month, to accommodate the blogging blitz that always accompanies the SEG Annual Meeting. If you're looking forward to hearing all about it, you can make sure you don't miss a thing by getting our posts in your email inbox. Guaranteed no spam, only bacn. If you're reading this on the website, just use the box on the right →

Open geoscience goodness

I've been alerted to a few new things in the open geoscience category in the last few days:

  • Dave Hale released his cool-looking fault detection code
  • Wayne Mogg released some OpendTect plugins for AVO, filtering, and time-frequency decomposition
  • Joel Gehman and others at U of A and McGill have built WellWiki, a wiki... for wells!
  • Jon Claerbout, Stanford legend, has released his latest book with Sergey Formel, Austin legend: Geophysical Image Estimation by Example. As you'd expect, it's brilliant, and better still: the code is available. Amazing resource.

And there's one more resource I will mention, but it's not free as in speech, only free as in beerPetroacoustics: A Tool for Applied Seismics, by Patrick Rasolofosaon and Bernard Zinszner. So it's nice because you can read it, but not that useful because the terms of use are quite stringent. Hat tip to Chris Liner.

So what's the diff if things are truly open or not? Well, here's an example of the good things that happen with open science: near-real-time post-publication peer review and rapid research: How massive was Dreadnoughtus?

Technology and geoscience

Napa earthquakeOpen data sharing has great potential in earthquake sensing, as there are many more people with smartphones than there are seismometers. The USGS shake map (right) is of course completely perceptual, but builds in real time. And Jawbone, makers of the UP activity tracker, were able to sense sleep interruption (in their proprietary data): the first passive human-digital sensors?

We love all things at the intersection of the web and computation... so Wolfram Alpha's new "Tweet a program" bot is pretty cool. I asked it:

GeoListPlot[GeoEntities[=[Atlantic Ocean], "Volcano"]]

And I got back a map!

This might be the coolest piece of image processing I've ever seen. Recovering sound from silent video images:

Actually, these time-frequency decompositions [PDF] of frack jobs are just as cool (Tary et al., 2014, Journal of Geophysical Research: Solid Earth 119 (2), 1295-1315). These deserve a post of their own some time.

It turns out we can recover signals from all sorts of unexpected places. There were hardly any seismic sensors around when Krakatoa exploded in 1883. But there were plenty of barometers, and those recorded the pressure wave as it circled the earth — four times! Here's an animation from the event.

It's hard to keep up with all the footage from volcanic eruptions lately. But this one has an acoustic angle: watch for the shockwave and the resulting spontaneous condensation in the air. Nonlinear waves are fascinating because the wave equation and other things we take for granted, like the superposition principle and the speed of sound, no longer apply.

Discussion and collaboration

Our community has a way to go before we ask questions and help each other as readily as, say, programmers do, but there's enough activity out there to give hope. My recent posts (one and two) about data (mis)management sparked a great discussion both here on the blog and on LinkedIn. There was also some epic discussion — well, an argument — about the Lusi post, as it transpired that the story was more complicated that I originally suggested (it always is!). Anyway, it's the first debate I've seen on the web about a sonic log. And there continues to be promising engagement on the Earth Science Stack Exchange. It needs more applied science questions, and really just more people. Maybe you have a question to ask...?

Géophysiciens avec des ordinateurs

Don't forget there's the hackathon next weekend! If you're in Denver, free come along and soak up the geeky rays. If you're around on the afternoon of Sunday 26 October, then drop by for the demos and prizes, and a local brew, at about 4 pm. It's all happening at Thrive, 1835 Blake Street, a few blocks north of the convention centre. We'll all be heading to the SEG Icebreaker right afterwards. It's free, and the doors will be open.

Great geophysicists #9: Ernst Chladni

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?


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!