Hayward Fault Creep - Fremont, CA - Places of Geologic Significance on Waymarking.com

The Hayward Fault one of, if not the, most active fault in California. Unlike it's rival the San Andreas Fault, which almost never moves, the Hayward fault slips constantly creating for some really interesting geology. What's even more interesting is that land developers believed it was a good idea to build houses literally right onto of an active moving fault. Some of these houses are crooked and jagged. Parking for this earth cache can be found at or neat the above coordinates. Please don't park in the driveways or block anyone in. This is a neighborhood too.

The Hayward Fault begins as the Calaveras Fault which begins at the San Andreas Fault about 20 miles south of famous Hollister, also known for it's fault creeps. A creep, in geology means a fault that is actively moving with little to no friction. This is due to the abundance of talc in the area. Talc is a natural rock that is rated a 1 on the rock hardness scale where on the other end, a diamond is rated a 10. The talc is then pressed together where it is broken down into a powder, acting as a lubricant for the fault to move whenever it receives a force from the earth.

Before I go into any more details lets first discuss the basic fundamentals of how fault lines are created and now they work. The answer can be found in your kitchen, literally. When boiling pasta on the stove, the hotter pasta floats to the surface then when it cools it sinks. This effect has a name. Convection currents in your pot at home and in the earth are nearly identical. There are a few difference though. One is with water, rather than boiling rocks and the other is that one is less a few inches while one is miles deep. Convection currents are continues cycles in the earth's mantel that make hotter rock rise, and cooler rock fall and the cycle begins over and over again. When this happens, it causes fractures in the earth's crust. When fractures occur, a fault line is created.

At this site you can observe something special along the Hayward Fault. Sometimes, or actually most of the time, the fault isn't just a straight line down the crust. It's jagged and at an angle. There are two types of these transverse (strike-strip) faults. One is called normal and the other is called reverse or thrust. The way to tell the difference is to see where the hangwall and footwall are in relation to each other. If the footwall is higher than the hangwall, then it's a reverse transverse fault. If the hangwall is higher than the footwall, than it's a normal transverse fault. Refer to the chart below that can give you a better sense of what to look for.

The Hayward Fault is a right lateral fault. This means, if you are on one side of the fault, looking at the other, the other side would move to the right relative to you.