Not to be too much of a party pooper, but I highly doubt that seismic activity was related to the work on the water tower. Without knowing exactly where the sensors are set up, there's nothing that looks like it's a greater magnitude than a large truck driving past the site. When I lived in California for several years, I learned that nothing under about 2.5 was even noticeable, and it really wasn't worth reporting anything less than about 3.5 (other than for purely scientific endeavors). Nothing on this chart appears to be greater than 1.0
The most active period on the graph is from around 9:00-11:00pm. I have a tough time believing that the crew was doing their major demolition project at the same time that they were setting off fireworks around the resort and huge volumes of traffic were passing by along World Drive without noticing the work. They likely didn't arrive on site until around that time, with the bulk of the work taking place after midnight
Furthermore, unlike the video posted earlier in this thread, I suspect this was a highly controlled demolition, due to the buildings and roads surrounding the tower. They most likely removed the 'tank' from the top with a crane and set it on the ground, and then used the crane to slowly lower the support structure to the ground, before dismantling them into pieces to be taken off site. It's not nearly as dramatic as having it tumble over, but would be entirely necessary for the semi-confined location. It's hard for me to believe that type of controlled work would be caught on a seismograph a few miles away