It's strange to wake up in the middle of the night because your bed is rattling, but that's perfectly normal for most citizens of Santiago!
Because big terromotos are also fairly common here, Chileans need to be prepared to deal with quakes powerful enough to destroy buildings, cut off communications, and create tsunamis ("tidal waves") that can destroy coastal cities. The most powerful earthquake ever recorded (magnitude 9.5) occurred in Chile in 1960. Earthquakes of magnitude 7.0 or higher occur at least every couple of years in Chile, so the community and the government need to be ready.
Chile has multiple active faults, which are fractures in the Earth's crust that release energy, causing earthquakes. These faults are a result of plate tectonic forces, the movement of giant sections of the lithosphere, which is the outermost layers of dirt and rock on the surface of the planet. Basically, the rocky outer layers of the Earth shift around, which is why we now have separate continents with ocean in between. You might remember learning about Pangaea, a single giant continent in the time of the early dinosaurs that eventually separated into the continents we have now.
These giant plates of earth on which all the continents are sitting are still moving (very slowly) today. Some are moving away from each other, like the North American Plate and the Eurasian Plate (Europe). Others are moving toward each other. When this happens, one plate can slide under another in a process called subduction.
