Tuesday, June 26, 2012

DISC 19 Tokyo (25 June)

Tokyo as a wonderful visit and DISC with 53 in attendance.  This is the 19th DISC and brings the total 2012 DISC attendance to 955.  And we still have several stops to go later in the year.

My contact was the very able organizer Hideki Saito of OYO and SEGJ.  It was very nice to see recent University of Houston PhD grad Ayato Kato and Prof. Hitoshi Mikada of Kyoto University (very cool web page for geophysics).  I learned from Hitoshi that the work load of Japanese professors is immense... he advises 14 graduate students, teaches 6 courses per year (up to 200/class in some of them and no teaching assistant to help grade), and he maintains an active funded research program.  I will never again complain about the life of a US professor. 

The venue was a great presentation room at AIST near my hotel in the la Daiba area.  Like all of Tokyo, this is an area of amazing engineering:  An auto tunnel under the ocean bay right outside my hotel window. a bridge with roadway on top, trucks and train on lower deck, and a building that looks like a Menger sponge with a sphere attached.  Crazy and beautiful.  Oh, and it all works.

After the class, my host, the professor and some students of his took me out for a few beers.  We sat outside overlooking the harbor as night fell on Tokyo.  A beautiful evening with good company and a world-class view.  Thanks to all.

Tokyo DISC 2012

Recent UH graduate Dr. Ayato Kato

Evening beers with Prof. Mikada (far back left), Hideki Saito (far back right), and students.

A grand view

The Menger sponge building with sphere as seen from the beach.

A side trip to Kamakura found many beautiful things.

Our trusty mascot Niffy takes in a final breathtaking view of Tokyo before heading home.

DISC 18 Beijing (21-22 June)

The Beijing DISC was held in Zhouzhou city, which is southwest of Beijing itself.  With the airport on the northeast side of Beijing, this means a 50 mile taxi ride.  But I was met by Prof. Jie Zhang of the University of Science and Technology of China (USTC), and my very capable handler Bai Yubao of CNPC.  The DISC was sponsored by BGP who is gratefully acknowledged.  

Attendance was 100, making it the 2nd largest DISC audience behind Calgary.  But one gets the feeling Beijing could have 200 without any trouble.  Interpretation was expertly handled by Liu Yongxia of CGGVeritas, who turned out to be a graduate of CSM / CWP just like me (although a few years later).  Always nice to run across a fellow Oredigger fan out there in the big world.

Of note is 85 year-old S. X. Qian who sat on the front row, asked questions, and is working his way through my book Elements of 3D Seismology.  He is good friends with Roy Lindseth who was at my Calgary DISC.

The DISC in progress

The Beijing DISC class of 2012

About town

Zhouzhou City is far from the city crowds

My host Bai Yubao, a nice and very capable fellow.

S. X. Qian at 85 and going strong  

Back in Beijing for an afternoon it was time for sightseeing

Saturday, June 23, 2012

DISC 17 Nanjing (18-19 June)

The Nanjing DISC was a great opportunity for me to see China for the first time.  The attendance was a healthy 72 and we had simultaneous English-Chinese translation from the very capable Xiaohui Zhou.  Sinopec was the sponsor for DISC and a couple of excellent banquets.  It was disappointing to find out that Google Blogger seems to be blocked in China, so all the good DISC info on the Seismos Blog (including this entry) cannot benefit those who attended this class.  

YouTube is blocked as well, which is too bad because they cannot see this video of me out and about in Nanjing.  

Anyway, many thanks to Sinopec and my new friends in Nanjing.  

My handy organizer Zhu Hailong and the class

Signing books (photo by Yu Shao)

About town

Xiaohui and her husband gave up a Sunday to show me around the city.  We went to the famous Yangtze river bridge then Confucius temple area.  This is a great place for shopping and visiting the temple itself.  I got an English tour of the fascinating history of civil service examinations in ancient China.  In modern times, the test was given every 3 years an lasted 9 days, during which the 30,000 participants were confined to small cells.

After the DISC, I got a fine tour of the Sinopec Geophysical Research Institute by the president Mr. Qu Shaoli.  It is a first class facility with physical modeling lab, rock physics equipment, and an impressive computing facility.

A tour of the Confucius temple.  My translator, Xiaohui, on the right.

Table all set for a Chinese banquet 

Sharing food and drink with Mr. Shouli, president of the Sinopec Geophysics Research Institute

A fine tour of the Institute by Mr. Shouli himself.  Impressive.

Another DISC done, instructor and mascot are now off to Beijing.  (Photo by Yu Shao)

Friday, June 15, 2012

DISC 16 Paris (14 June)

The Paris DISC was sponsored by CGGVeritas (thank you) and held in thier excellent conference room at the office in Massy. The head count was 50, including friends and dignitaries Julien Meunier (the 2011 DISC), Shuki Ronen and Kamal Al-Yahya (who could only drop by for a while and did not get in the photo).  After the class I had a very nice chat with all of these luminaries over a glass of Bordeaux.

Front row far left is Shuki Ronen next to Julien Meunier.

An action photo from the audience.

Feed back and Q thoughts

One interesting thing was a very bright guy (Patrick Rasolofosaon of IFP) who pointed out that attenuation curves for the standard linear solid (SLS) and Biot theory are not quite the same; SLS has a symmetric attenuation curve in log-frequency, while Biot is a bit asymmetric. Since I have both Biot and SLS coded up in mathematica, I ran a test using gas sand parameters from Dutta and Ode (1983) to compute the Biot attenuation in dB/wavelength and then tried to fit this with SLS attenuation as b/Q where b is a fitting parameter.  The result (below) shows that Biot attenuation in these units can be very well fit by SLS attenuation.  I suppose one could argue that having Biot attenuation in dB/wavelength means it is an apples and oranges comparison.  Still thinking about that.

I am increasingly unhappy with one aspect of my DISC, namely the nature of my evidence that apparent and total attenuation are constant Q in nature.  Of course, there is Attewell and Ramana (1966) who clearly indicate that in situ attenuation estimates across a broad frequency range is linear with frequency (implying constant Q).  But my demonstration of constant Q from log data and broadband amplitude decay is weak. In searching for more direct and clear evidence, I have come up with a couple of ideas.  First, if constant Q attenuation behavior is present in real data then we should be able to show it from the following simple argument. The constant Q amplitude model is
Ax = Ao exp[ - (pi f x) / (v Q) ]
where Ax is the peak amplitude of a wave with frequency f after traveling a distance x with velocity v through an earth with a quality factor of Q (independent of frequency).  If we are thinking about a zero offset reflection event at depth z, the distance traveled is x=2z which can be related to the reflection time by z=vt/2 or x=vt.  With this association, our decay equation becomes
Ax = Ao exp[ - (pi f t) / Q ]

Taking the log of both sides, we find
log(Ax) = C + Bf
C = log(Ao)
B =  - (pi t) / Q .
This says that if we pull out a window of data centered at time t, take its Fourier transform and plot the amplitude spectrum in log(amp)-linear(f) space... it should be a straight line.  A quick test on some off-the-shelf migrated seismic data (window = 4.5-5.5 s) gave the plot below.  
Interference effects (notches) can locally drag the spectrum down but there is no mechanism that can boost the spectrum above it's true value, so I have connected the peaks with a dashed red line. The linear trend is good in the signal band of 8-72 Hz.  It might be possible to do a quantitative Q estimate from the line slope, which would be total Q (intrinsic and apparent) for the overlying rock column.  Anyway, I think this is a compelling argument that attenuation in real data is well-modeled by constant Q.  In the DISC book I argue this observed attenuation below 100 Hz is a combination of weak intrinsic viscous attenuation and strong layer scattering attenuation of O'Doherty-Anstey type that behaves like constant Q. My other idea about constant Q evidence involves Backus averaging, but that will have to wait for a later post.  

About town

I had about about a day and a half in Paris before the DISC, so I took the train to Notre Dame a couple of times.  The first trip was recon and find out what time things opened.  The next day I went in early and walked through Notre Dame at about 8am, it is a lovely place when you have it to yourself.  Also, the morning light made for some great photo opportunities.  

Le Grenier de Notre-Dame.  The best vegetarian restaurant in the world?  I vote yes

Mascot Niffy takes in the Paris scene

Notre Dame in morning light

Notre Dame, 8 am, all to myself:  A beautiful thing.

A roman passageway in the Crypte Archéologique near Notre Dame.

"Doubt is not a very agreeable state, but certainty is a ridiculous one"

The Sorbonne, no visitors.  Wonder if Voltaire could get in?

Sunday, June 10, 2012

DISC 15 Copenhagen (2 June)

The Copenhagen DISC was a bit different.  Where we have been seeing class sizes from 20-50 across Europe, here we had just 5.  Maybe an advertising problem, or a repercussion of the SEG taking over the entire DISC program when it had been a joint SEG/EAGE program in previous years.  However, we had a great conference-style room in the amazing Bella Sky hotel and the small group allowed us to be very informal.

About town

Copenhagen in June still required several layers of clothing.  Many outdoor cafes had heaters and blankets, but they lacked the shoulder-height glass windbreaks I saw in Stavanger.  Food at places along the canal was excellent.  My hotel (Bella Sky) was another matter.  This is a big hotel attached to the conference center with 800 rooms, but the cafe menu has a total of two sandwiches and maybe six main courses. If you stay here a week, it is easy to get tired of that menu.  One night I came in late and needed dinner in the room.  I checked the room service menu and found the two sandwiches and six mains, all with meat.  Well, I eat seafood or vegetarian and this was a dilemma. Ultimately I ordered the chicken and bacon sandwich, hold the chicken and bacon.  Not much of a sandwich and it took 1.5 hours to get there.  It is a beautiful hotel, but come on.

Hotel issues aside, I found old Copenhagen charming.  There were some good bookshops too.  I bought a couple of crazy books from the 1930s by Dennis Wheatly, the titles being Murder off Miami and Who killed Robert Prentice? (info here).

More bikes than cars in Copenhagen.

17th Century observatory tower with interior spiral ramp.

Fun Sercel party at the Carlsberg brewery.  Jim Gaiser with old beer truck.

This was my favorite.

DISC 14 Stavanger (31 May)

We had an excellent DISC in Stavanger with 41 in attendance.  The venue was a nice lecture room at the University of Stavanger (that seemed like a good school).  In the audience was my friend Rian de Jong of Shell whom I met years ago on a consulting trip to Oman.  Back then, he and friends took me on a weekend jaunt along the coast road south of Muscat, then up into the high country to look at wadis and ancient villages.  Rian's hobby is jetting around the world to see total solar eclipses.  He put me on to NASA's Fred Espenak,  the utmost guru on such thins... have a look.

Anyway, we had some discussions that were quite interesting.  It was a very good group.


From: Andrew James Carter 
Date: Thu, Jun 7, 2012 at 8:41 AM
Subject: Re: 2 quick feedback items

Hi Chris,

Two things arising from the [Stavanger] DISC that I can quickly send some feedback on:

1.   Transforming from Thomsen parameters to stiffnesses and back again.

I’m sure that by now someone else has already remarked on this, but in both your Backus Number article and the DISC book you don’t mention that whilst going from stiffnesses to Thomsen parameters is unique, going in the other direction is non-unique. Because of the quadratic relation between delta and the stiffness components it is necessary to choose the sign of (c13 + c55) (Voigt notation) in going from Thomsen’s parameters back to stiffnesses. This is dealt with in Tsvankin’s 2001 book on page 19. I think it’s a good idea to mention this when providing equations to go from Thomsen’s parameters to stiffnesses in case the unlikely event happens that one day someone stumbles upon a geological material of importance that violates this assumption.

2.  Definitions of Q. 

I agree with you in general about avoiding unnecessary approximations that can lead to hidden errors, although a high-Q approximation simplifies matters if you choose to use a different definition of Q than the one you and Kjartansson use! A particularly good reference on definitions of Q is O’Connell and Budiansky (1978). This paper explains the relation between the definition of Q that Kjartansson uses and Futterman’s choice of definition. I prefer Kjartansson’s choice as it is better behaved for strong attenuation and has a simpler relation to the complex modulus in the wave equation, and it allows the development of Kjartannson’s elegant CQ model. The point is though, as long as you are working in a high-Q approximation the difference between the two definitions is not especially significant, but once you choose to write everything out exactly, it is necessary to remember that you are using a different definition of Q than, for example, Aki and Richards. Aki and Richards used what I refer to as the “2pi definition” as opposed to the “4pi definition”, as did Futterman. I’m afraid I haven’t had time to check through the start of your attenuation chapter yet, but I will try to do so for my own satisfaction if I get time. I couldn’t see anything wrong after a quick look through though. I do think it might be useful for your readers to be aware that different attenuation laws e.g. Kolksy-Futterman and Kjartansson use different definitions of Q, and that these differences begin to matter at Q values that could actually be encountered locally within seismic sections containing highly attenuative zones.

Some evidence regarding 1d-scattering attenuation/stratigraphic attenuation that conflicts with some of your argument to follow when I get a bit more time.

Best regards,


About town

Even in late May, Stavanger is a cold and windy place, although they tell me I saw it on a very balmy day.  Still, it was windy, damp and cold.  The Norwegians have a saying: "There is no such thing as bad weather, only bad clothes."

The big boats come in very close with Stavanger's deep water harbor.

This town is proud of it's role in oil and gas.  No such thing in Houston.

Sam and interesting wall art.

No idea, but someone thought she might be getting married.

Monday, June 4, 2012

DISC 13 Aberdeen (29 May)

The Aberdeen DISC was held at the Copthorne Hotel with 24 attending. There were some hiccups at the beginning about a projection screen that was too small for the job and slide images being cropped top and bottom.  But we soon had a big screen and fixed the cropping problem.  From there it was clear sailing.  

About town and country

The short hop from London to Aberdeen was little more than an hour, but it took us from the bustle of a city in full-tourist season getting ready for the Queen's Jubilee and the Olympics to a quiet Scottish town.  It is a gray place: The name 'Granite City' is well-dserved, I never saw a house made of wood.  The big plan here was a pilgramige to St. Andrews, the birthplace of golf.   

On Sunday we rented a diesel VW Golf that got about 50 MPG (why don't we have these in the states?), and wisely opted for the navigation system.  My daughter Sam was still visiting from Ontario, so she served as navigator.  I have driven on the right side of the rode a few times, so it came back pretty quickly.  But, according to Sam, I did seem to have an alarming tendency to crowd the left-side of the road and get halfway through a roundabout and accelerate to the exit road.

We took a reconnaissance trip Sunday afternoon down the coast road toward Dundee.  We stopped at two grand castles, Dunnotar and Edzell.  Back in Aberdeen that night we attended Legally Blonde The Musical, which was an absolute joy.  See it if you can.

On Monday, we headed for St. Andrews with Jill Abbott (my SEG handler) along for the ride.  She agrees with Sam about my slingshot driving through roundabouts.  Surely the Old Course at St. Andrews could not live up to 30 years of expectation, but somehow it did.  Knowing all the stories of Old Tom Morris and his son Young Tom, Nicklaus, Watson, and the failed dreams of a thousand more.

One order of business was finding a hat.  My best Scottish hat was lost at the summit of Mt. Evans outside Denver in a 70 MPH gale last summer.  I was up there with Sam who was working at LASP in Boulder, a group she returns to this summer to pursue a PhD in Aeronautical Engineering.  Anyway, we found the hat.  Cashmere, made in Scotland and bought on a street walked by Old Tom.  As it should be.

One rushed afternoon in St. Andrews is not enough.  I shall return.
Sam and the long walk to Dunnotar Castle

Edzell castle

Comfy, our mascot, and the musical program.

The Old Course at St. Andrews and the R&A Golf Club

The new hat