In this short exercise, you will use some animations of fault blocks to explore the different kinds of faults and the forces that cause them.
Click on the links below to open up movies that show how two blocks slide past each other.
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Think of the saw cut as a fault along which one block moves relative to another. Note how the upper block (above the fault) moves relative to the block below the fault. Notice also whether this motion increases or decreases the thickness of the block where the two halves overlap. The fault shown in this movie results when the two blocks are pulled from the sides (tension).
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This fault has the opposite type of movement. Note how the upper block (above the fault) moves relative to the block below the fault. Notice also whether this motion increases or decreases the thickness of the block where the two halves overlap. The fault shown in this movie results when the two blocks are pushed from opposite sides (compression). |
These two types of motion along the fault in the block represent two of the main types of faults. If the upper block moves down, which would be the normal thing that would happen if the blocks just slide apart, it is a normal fault. Normal faults require the blocks to be pulled apart (tension). If the reverse happens, and the block must be pushed up, it is a reverse fault (compression).
In this movie, the blocks move horizontally relative to one another. This type of fault is a strike-slip fault. If a strike-slip fault is a boundary between tectonic plates, it is also called a transform fault. Motion along a strike-slip fault can offset a feature either to the right or to the left. If a strike-slip fault offsets a feature on the opposite side of the fault to the left, it is called left lateral, and is right lateral if it offsets a feature on the opposite side to the right. The San Andreas fault of California is a right-lateral strike-slip fault, and is a transform fault.
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Note: You do not need to complete an assessment in Canvas after examining these movies and thinking about different types of faults, but the principles you learn here will be used elsewhere in this module.