No, it's not the San Andreas Fault. When people think of dangerous faults in the United States, the San Andreas fault likely comes to mind. But despite its notoriety, there is another potentially greater threat located in the East Bay region of Northern California. It is known as the Hayward Fault, and it could produce the greatest natural disaster ever to hit the US. Although the Hayward Fault is shorter than the San Andreas, what it lacks in potential magnitude, it makes up for with proximity to major cities, lying directly under structures where many people live and work. The San Andreas cuts predominantly through remote areas, whereas the entire length of the Hayward Fault runs through densely populated cities such as Oakland (pop. 406,000), Fremont (pop. 224,000), and Berkeley (pop. 116,000), and is not far from San Francisco (pop. 805,000) and San Jose (pop. 945,000). Given the Hayward's proximity to large populations, its rupture presents a huge risk. In fact, the U.S.