Since we were talking about sounds on this and a previous thread, the Nova (PBS) I saw last night had a segment on humming deserts. I bunch of MIT researchers would slide down a sand dune on their butts in Death Valley to get it humming. They did not state whether they were wearing special underwear (They were wearing shorts). I have an idea for a "Preparation H" commercial! If the wind is right the Dunes will hum all by themselves. But, they determined that it was not the wind...it is the sand sliding down the slip faces. The Dunes need to be >30 m-high, and the sand grains need to be very uniform size and to be loose but above a compacted layer. The tone depends on the shape and size of the dune, and the depth to the compacted layer. I guess the sand grains being all the same size allows the vibrations to get into resonance....the example they butt-slid to start was just below 100 Hz. So, what does this have to do with earthquakes? Who knows, maybe some little creep on a fault (No, I don't mean an unpleasant geoscientist at the surface) might get uniform gouge grains all excited.....and somehow get some kind of emission going.....This is not the same as stressing a big solid piece of rock.
Hey, does anyone know what causes the Moodus Connecticut sounds? Are they before or during the small quakes there?
Chris