What Is a Geologic Fault?
A geologic fault is a fracture or zone of fractures between two blocks of rock in the Earth's crust. Faults allow the blocks to move relative to each other. This movement can be sudden and rapid, causing an earthquake, or it can be a slow, gradual process known as creep.
Section 2: The Main Types of Faults
There are three primary types of faults, classified by the direction of relative movement. A **normal fault** occurs when the block above the fault (hanging wall) moves down relative to the block below (footwall), typically caused by tension. A **reverse fault** is the opposite, where the hanging wall moves up due to compression. In a **strike-slip fault**, the blocks slide horizontally past each other.
Section 3: A Practical Example
The San Andreas Fault in California is one of the most famous examples of a strike-slip fault. It marks the boundary between the Pacific Plate and the North American Plate. The horizontal sliding motion along this fault is responsible for many of the earthquakes that occur in the region.
Section 4: Importance of Studying Faults
Understanding and mapping faults is critical for seismic hazard assessment. By identifying active faults, scientists can better predict which areas are at a higher risk for earthquakes. This knowledge helps inform building codes, infrastructure planning, and public safety measures to mitigate potential damage.