Friday, February 15, 2008

Slow global warming - stop earthquakes!

Last Thursday's journal club was something of a milestone for me - my first even semiformal presentation on a scientific topic since high school, and for an audience of people who already have degrees in (or have already partly completed degrees in, at least) seismology. Journal club is laid back and conversational and not for any sort of grade or credit, which really gave me no good reason to be worrying about it, but I was worried nevertheless.

My job was to summarize seismological happenings in Nature since December, of which there have not been very many. Of the two earthquake articles I found (there was also a volcano article, which I did not realize was fair game until after the presentation), I went a little more in-depth on one summarizing an experiment simulating stick slip events in fault gauge particles using glass beads and low-frequency sound waves. The experimenters built a rig that applied constant stress to the beads, and could apply pulses or prolonged sounds if desired. Without the sound waves, the recurrence interval and stress drop of the stick slip events was constant and predictable, but as soon as one pulse was thrown into the mix, the recurrence interval became unpredictable and the stress drop fluctuated more. The aim was to try and see how a bombardment of long-distance seismic waves across an unrelated fault triggers new quakes, and to see if there was any pattern to it that could be used for the sake of predictions. There was no pattern, and I had a few questions about the method (such as the size of the beads, or whether or not the direction from which the pulses came made a difference on the results), but the consensus of everyone at the meeting was that these were valid questions that hopefully were covered in some supplement to the article somewhere, since these things really shouldn't have been left out.

And it turns out that worrying was, as I should have expected, not a thing I needed to be doing. People asked questions after I was finished, which answered as best I could, and then there was some further discussion of long-distance triggering. It didn't seem to be any more or any less discussion and questioning than after anyone else's presentation that I've seen so far, and one of the faculty told me it was a "very good kind of unremarkable," and that I would have definitely been told if I'd screwed up. Now that I know I've done well once, the next time should be easier.

The other person who presented last Thursday chose to focus in on a paper dealing with carbon dioxide released from faults during large earthquakes. The theory is that there is enough friction in larger quakes to melt a small amount of the rock in the fault, which releases gas. I thought it was an interesting article, but the way the title was worded made it sound like a disastrous global-warming-related phenomenon. I forget the exact wording, but at first glance, it seemed like the article might actually be some far-fetched thing about how faults, when just sitting there, are spewing greenhouses gases. I was glad that was not the actual content, but I have to wonder if the title was carefully formulated to grab attention in a time when global warming is such a focus. It was also certainly good for a long string of "stop plate tectonics" jokes, though we all agreed that volcanic emissions should be targeted for reduction first...

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