Unsolved problems in applied geophysics

The most famous list of unsolved problems came from the mathematician David Hilbert in 1902. Adapting his language slightly:

Who of us would not be glad to lift the veil behind which the future lies hidden; to cast a glance at the next advances of our science and at the secrets of its development during future centuries? What particular goals will there be toward which the leading [geoscientific] spirits of coming generations will strive? What new methods and new facts in the wide and rich field of [geoscientific] thought will the new centuries disclose?

— Adapted from David Hilbert (1902). Mathematical Problems, Bulletin of the American Mathematical Society 8 (10), p 437–479. Originally appeared in Göttinger Nachrichten, 1900, pp. 253–297. Available online.

There have been other, similar efforts in various fields:
 * The Millenium Prize — in mathematics, from the Clay Institute
 * Science Magazine
 * Chemistry
 * List of unsolved problems — in all sorts of fields, collected on Wikipedia

Papers
There have been a few papers on this topic, mostly on the broader questions of geophysics. Some examples:
 * Some unsolved problems of geophysics — Leason Adams, 1947.
 * Quo Vadimus: Geophysics for the Next Generation — G. D. Garland and J. R. Apel, 1990.

There are some in geology too:
 * On some unsolved problems in geology — by John Dawson, 1883
 * Five outstanding questions in earth science — Earth Magazine, 2012

And in applied geophysics and reflection seismology:
 * Addressing Milo's challenges with 25 years of seismic advances — Larry Lines, 2005.

Backus's challenges in 1980
These were published in 1980, when Milo Backus was president of SEG. I don't have the original paper (anyone?), but the problems themselves are quoted in Lines, 2005:


 * 1)  Our current seismic image of the subsurface is most imperfect.
 * 2)  Our ability to deal with the effects of lateral heterogeneity on seismic transmission is very crude.
 * 3)  3D seismic imaging is still in its infancy.
 * 4)  “Direct” hydrocarbon detection is still generally limited to only the most blatant fluid content anomalies.
 * 5)  Our quantitative estimates of subsurface elastic properties are still very crude and incomplete.
 * 6)  We have not yet nailed down the nature and magnitude of high-frequency loss—the only fundamental limitation of the seismic method.
 * 7)  We are just beginning to recognize that the earth is a solid—the next generation can recognize its anisotropy.
 * 8)  We still tend to view the subsurface impedance as white and Gaussian.
 * 9)  We have not established the degree of ambiguity inherent in our inverse problem.
 * 10)  We have made only a small beginning in our use of the huge information content available in exploration geophysics results to illuminate geologic processes and geologic history.

Unsolved problems unsession 2013
In May 2013 we held a live brainstorm session at Canada GeoConvention in May. Topics were lightly oriented around 'integration'. The top problems we named and ranked in the session were, with rankings:

Interviews with Satinder Chopra
Satinder Chopra has been interviewing people in CSEG's Recorder magazine for over 12 years. Recently, he has been asking people about unsolved problems. These are (extensively) quoted and paraphrased; the originals are online.

Larry Matthews, Feb 2013
Interview with Larry Matthews


 * 1) If you are a seismologist working in Italy I would suggest the most important question is, “How can I predict destructive earthquakes so they don’t send me to jail?”
 * 2) Microseismic is an emerging technology in the oil and gas business that is being used extensively for the monitoring of hydraulic fracturing. There are no ends of questions to be answered here. What is the in-situ stress state of the earth, how are we modifying those stresses with our hydraulic fracture and how will that manifest in the microseisms that we detect and the production we ultimately realize? How are we going to figure out where proppant is going and what is the effective stimulated rock volume? What is the true value of microseismic information? The questions are growing faster than the answers right at this present time. So for younger geoscientists entering the business there is no end in sight to the topic areas of microseismic and geomechanics that I can see.
 * 3) The third revolves around the proliferation of technical information. [There is so much.] It seems to me there is an ongoing need to try to figure out how we can better synthesize all of this information. It’s overwhelming for most and so the tendency is – I can’t go there, because even if the answer I seek is available, I’ll be forever trying to figure out how to get it quickly and easily. So Library Sciences, IT and how we can continue to deliver pertinent, effective and meaningful information to the people that need it in a timely fashion is going to be a big and ongoing challenge.

Gerard Schuster, April 2013
Interview and Interview


 * 1) Extracting permeability from seismic data. Reliably determining saturation, porosity, crack density+orientation from seismic data are still challenges.
 * 2) Reliable subsalt velocity and images.
 * 3) Optimal and useful ways to combine different types of data such as seismic, gravity, and EM.

I find imaging of multiples very interesting, which I think will eventually be used as a useful complement to imaging primaries, not just an after- thought. Designing experiments that utilize both multiples and primaries will likely give you more bang for the buck, in some cases. Dongliang Zhang at KAUST and Yike Liu in China (and others) are doing some very interesting work in the area.

Larry Mayo, June 2013
Interview with Larry Mayo
 * 1) The simplest unsolved problem comes from data acquisition where surface conditions vary locally, either wiping out reflections or changing in depth through multiples or mode converted noise. Acquisition parameters are set to best get the average solution. Acquiring more data with more geophones with the mega channel cableless systems helps to improve the signal to noise and is a start, but comes at a cost. Interpolation has helped this issue tremendously from my experience.
 * 2) Passive seismic monitoring systems are being advanced with 4D and microseismic but are costly and dependent upon seasonality. Newer systems and techniques (borehole fiber optics) are being developed but are taking time to advance other than on a well-by-well basis where they should be applied to the field to get better recovery.
 * 3) It is hard to choose between two others! I have not found the ideal seismic interpretative workstation while on the other hand I believe that non-seismic methods have a future as another tool in the toolbox.

Blog posts

 * Unsolved problems
 * Ideas for open scientific questions
 * Cuestiones abertos de la geociencia

Google Moderator
Google Moderator is a tool for gathering and ranking questions in real time. I tried it out in 2010: Google Moderator. The top questions are shown to the right, but note that only 15 people participated. It would be fun to reproduce this exercise in a large room full of people.

Other disciplines

 * Lists of unsolved problems — Wikipedia meta-list
 * Unsolved problems in mathematics — Wolfram MathWorld
 * ...there are loads of others...