I digitized several IGN GPS station data and put it in one plot. Still haven’t gotten around to the Mogi yet. As noted yesterday, I’m going to have to make some assumptions about where the freaking magma chamber is at.
During the run up phase, I assumed (always be careful when you assume) that it was at about 15 to 17 km deep and 4.1 miles from stations FRON. That’s where I came up with the 750K m³/day estimate. (actually, 798,645 m³/d with 34.8 mm lateral displacement at FRON)
This covered the accumulation rate up until Bob went “pop” and the Jacuzzi started. (63,891,583 m³ total in the 80 days until eruption) If you also assume that Bob has been acting as a relief valve (well, Bob and any related but unseen vents) then you can take the relatively flat GPS displacement to mean that Bob and crew are venting off what is accumulating in the chamber.
That puts the effusive rate at the 750K to 800K m³/d level.
I haven’t done a new Mogi yet…. mainly since I’m not really sure where to stick the chamber. (no, I am not sticking it there, that would be physically impossible) Another reason is that I’m still rummaging around to find my spreadsheets. (eight drives and a couple of TB of crap scattered all over the place)
And… the third reason, which I mentioned earlier, is that I think that the current distortion field shows a shallower and possibly bifurcated chamber(s).
Larger picture http://i40.tinypic.com/ibml8i.jpg
The positive values east of FRON are crap. There is no positive displacement east of FRON in the data! It shows up in the plot like that due to the way that the quadratic surface deals with fitting the available data points. As noted on the plot, lines of bearing to the stations east of FRON show a negative displacement. (IZAN, LPAL etc) This means that FRON and those stations are closer together.
What is important in that plot, is the area west of FRON. Thats the direction of Sabinosa and Los Llanillos.
In that direction, there are two really strong displacements straddling a not so strong displacement. Where the color bands are squashed together are going to be the locations that have the most displacement… and if there is uplift (which we can’t see from IGN’s truncated GPS data) it’s going to be at those points.
Now my most recent plot
Larger picture http://i39.tinypic.com/ta3pg5.png
This is a running plot of the IGN GPS data and the quakes (with depth) that was going on at that time. As you can see, the displacement settled down to a pretty constant level once Bob started.
The disturbing thing to note, and the part that is used in the previous map style plot, are the last few days. Something kicked the displacement into high gear. Don’t know what. That is what makes me think that there may be a shallower set of magma accumulations.
As for the idea of it being hot water… nah. If water gets hot enough to expand to that amount of pressure (to cause the observed distortion) it would have ruptured the surface and we would be looking at geysers.
Well, there are the plots and my take on it. I’m not a geologist… so I could be wrong.
It may or may not be correct, but I have read papers that postulate that the El Golfo slide may have generated decompression melting. I have no idea how long this goes on, but I found it curious that one day, this swarm just started out of the blue. To me, its as if the magma formed in place and started moving. Now, after Bob has taken some stress out of the system, new material gets mobile.
Ruminate at you leisure.