Focal mechanism fault types are classified based on the orientation and movement of faults during an earthquake. The classification typically includes three primary types of faulting mechanisms:

1. Strike-Slip Faults: These occur when the movement along the fault is predominantly horizontal. The fault plane is vertical, and the blocks move sideways past each other. Strike-slip faults can be further classified as right-lateral or left-lateral, depending on the direction of movement.

2. Normal Faults: In normal faults, the block above the fault plane (the hanging wall) moves downward relative to the block below the fault plane (the footwall). This type of faulting is associated with extensional tectonics, where the crust is being pulled apart.

3. Reverse (or Thrust) Faults: Reverse faults occur when the hanging wall moves upward relative to the footwall. This type of faulting is associated with compressional tectonics, where the crust is being pushed together. Thrust faults are a type of reverse fault with a gentle dip.

These fault types can be visualized using focal mechanism diagrams, often referred to as "beach balls," which represent the orientation of the fault plane and the direction of slip. The classification can also be displayed using ternary diagrams, such as the Kaverina-type classification, which helps in visualizing the distribution of different fault types based on their focal mechanisms.

For more detailed information, you can refer to resources like the Wikipedia page on Focal Mechanism or the IRIS educational page on Focal Mechanisms.

Here is an image illustrating the different types of focal mechanisms:

Focal mechanisms are used to classify earthquakes based on the type of faulting that occurred. According to the search results, there are several ways to classify these fault types:

1. Strike-Slip Faults: These are faults where the two sides of the fault slide past each other horizontally. They can be further classified as right-lateral or left-lateral based on the direction of movement.

2. Normal Faults: In normal faults, the hanging wall (the side above the fault) moves down relative to the footwall (the side below the fault). These are typically associated with areas of tensional stress and are common at divergent plate boundaries.

3. Thrust Faults (Reverse Faults): In thrust faults, the hanging wall moves up over the footwall. These are associated with compressional stress and are common at convergent plate boundaries.

4. Oblique Faults: These faults have a component of both strike-slip and dip-slip motion. They can be further divided into oblique-normal and oblique-reverse based on whether the dip-slip component is normal or reverse.

The classification of focal mechanisms can also be represented using ternary diagrams, which show the distribution of double-couple focal mechanisms according to the standard classification. Images from the search results, such as the one from Wikipedia (Focal mechanism), illustrate the beach ball diagrams that are commonly used to represent these focal mechanisms, showing the orientation of the fault and the type of motion that occurred.

In summary, focal mechanisms are classified based on the type of faulting that caused the earthquake, with the primary categories being strike-slip, normal, and thrust (or reverse) faults. Each of these can be further subdivided based on additional characteristics of the fault motion.