Resizing and Transparency of Earthquake Spheres in Animation

I would like to request the ability to resize the earthquake spheres to a smaller size than .1 and other sizes in between the current available ones. I suggest a scrolling bar for sphere sizing.  In addition to that, I would  like that during an animation, after a new earthquake appears, the old earthquake(s) become transparent, thus allowing a specific earthquake to be focused on during an animation. Thanks! :)