it's a constant, straight line rise, but the rock is resisting more, because space is at a premium down there, hence the jumps.

[link to i44.tinypic.com]

notice how neatly the line bisects all the quakes?

I believe the magma is inflowing at a constant, unchanging rate, and has done from the start.

I also think once the mag 4+ quakes stop, we might see bigger quakes. Think of it like a balloon inflating. first off there are wrinkles in the balloon, and as these smooth out we get the mag 3- 4 quakes.

eventually OUR balloon, in air, is fully inflated, but still growing, so now it gets bigger, and pushes out into the air, only there isn't air down there with all that magma, there's solid rock.

this is the way I'm seeing what is going on anyway.