Friday, June 29, 2007

Seismic Fishing

Throughout my long scientific career (now ended!), nothing got me more excited than pulling up a big 'fish' of new data. I've always regarded science as fishing on the edge of great ocean, and once in a while, pulling out something interesting (didn't somebody else think of that first?).

My very best fishing story was around the 80-90 decade boundary. We were looking for new nuclear sites, and this time, we actually had some money! (unlike the cheapies today!). We had heard rumours of 'sunken treasure', old seismic data, and we were looking for it. (This story has lots of credits to people who are smarter than me, yada, yada).

It turns out that at one time, the Michigan Basin was a really hot place to explore for oil. This attracted the 'spec data' seismic boats, who are the true high-rollers of the sea. They gather data on spec, and sell it to the highest bidder. The big boats came in up the St. Lawrence Seaway, and went out the same way. On the way out, they decided to trail their kilometers of equipment and 'shoot' Lakes Erie and Ontario.

This was in 1971, and 1985. The 1971 survey was done with Marine Vibroseis, which I still don't know how exactly it works, but these records went deep, right to the Moho! The 1985 survey was shot with conventional big airguns, which scare the fishies to death, and is very controversial now.

Well, these crazy guys just processed the first couple of seconds, and saw to their horror, there was just a thin crust of 'good' layered sedimentary rock, on top of a horrible swirly mess of granites. These sections got out into the wild, and were declared worthless by other scientists. The poor guys sent them down to their cavernous storage libraries.

Then we came along with our pockets jingling with coins. One of our experts noted that the data continued beyond their cut-off point, and might be good. We went down to Austin, Texas and looked at the tapes. It was amazing that they had saved everything, and it was all still readable! To cut this ramble short, they fell over themselves giving us a real cheap deal to process the data (in the hope they could sell the details!), mainly because we only required 'relative data', not accurate enough to actually sink an oil well.

Those gorgeous records showed magnificent structure right down to the Moho! Many papers were written, and we got an excellent view of the deep crustal structure under Ontario. Most of my subsequent endeavours (and windmill charges!) were guided by this. As expected, the 'pancake rock' (sedimentary) guys continue to ignore this.

Another day, and I'll dig up some of the sections.

2 comments:

monado said...

So this is yet another example of scientific serendipity: "He who seeks will probably find -- something else.

Now if we could just figure out why the powers that be are reluctant to use good data when it falls on them...

Harold Asmis said...

Unfortunately, power-people never read or write, they just react verbally. This leads to the usual 'situations'.