Specifically, where is the fault plane located at a normal fault? near the top? near the bottom?
The fault plane in a normal fault is located near the top of the fault line.
To understand this, let's first explain what a normal fault is. A normal fault is a type of dip-slip fault, which means it occurs when two blocks of Earth's crust move relative to each other along a vertical fault plane. In a normal fault, the hanging wall (the block above the fault) moves downward relative to the footwall (the block below the fault).
To determine where the fault plane is located, imagine a vertical cut through the Earth's crust along the fault line. The fault plane will be the inclined surface along which the displacement occurs. In the case of a normal fault, the fault plane slopes at an angle, dipping down towards the footwall.
Now, since the hanging wall moves downward relative to the footwall in a normal fault, the fault plane will be closer to the top of the fault line. This means that the fault plane is located near the upper portion of the fault, where the hanging wall originates. The footwall, on the other hand, is located below the fault plane.
It's worth noting that fault planes can vary in size and location depending on the specific geological conditions, so the fault plane's exact position may not be uniform in all normal faults. However, generally, the fault plane will be closer to the top of the fault.