Nearly every resident of California has experienced an earthquake. Even the youngest schoolchildren have the safety procedure drilled into them: duck under a table, hold on, and pray that it’s only a small one. Barring a truly catastrophic quake, the situation usually ends there. You go on with your day as if nothing had happened, the near catastrophe completely forgotten. Most people assume that the danger ends after the last remnants of the tremor share the ground. But there is a much more sinister side effect of earthquakes that affects daily life around California and much of the rest of the world: contaminating the groundwater supply.