Uploads from Tom Scott

You know in the first Jurassic Park movie, there was that scene with the glass of water in the car's cupholder, with ripples on it to show just how heavy the approaching T-Rex's footsteps were? Well, this thing behind me is technically called the "Large Mobile Shaker", but the folks here at the University of Texas? They call it the "T-Rex", because it's a machine designed to shake the ground itself. - We have five shakers. They go from a small one, that's right behind me. And we call that an "urban shaker" because you can bring it downtown and not get into trouble with shaking. And then we have very, very large ones, Liquidator and T-Rex. Liquidator is a low frequency vertical shaker where we generate surface waves. Like surface waves from earthquakes, but ours are linear, typically, and earthquakes can be non-linear. [loud vibration with descending tone] T Rex is a tri-axial shaker. Tri-axial means that the shaker, only one at a time, it can shake vertically, it can shake horizontally, and it can go transverse. It can go up to about 60,000 pounds force vertically, and about half horizontally. We have been all over the United States. We have sensors that we've designed and we will push in because there are pushing rams on the back of Liquidator and T-Rex, so that we can install sensors and then watch the wave go down. Many times we're watching the wave propagate away from us, but other times it's very helpful to watch the wave going down, and seeing how poorly the soil might behave due to large amplitude shaking, which is what you don't want. We just came back from Wyoming, where they're going to build new power plants, and the earthquake design is critical. And we generated a 6000-foot-long wave. Now we generated a two foot long wave, too, but going through the range. So that means we could evaluate the stiffness profile down to half a mile. With no boreholes! That is really a true accomplishment and a very, very cost effective addition to the design of the plant. So this is a sensor. It's a big magnet with a coil. The coil is going through the magnetic field. We were out there in Wyoming and the darn cows walked by. Fortunately, they didn't break any cables, but we had to stop testing because they made more noise. They were right out there and we were half a mile away. Oh, my goodness. Every time we go someplace, we'll make sure the level won't damage structures. Once we were on the UCLA campus, and maybe didn't watch what we were doing so much, and people came running out of the building. And that got us in trouble!