At transform boundaries, tectonic plates slide past one another horizontally. This movement is primarily characterized by shear stress, which can lead to several types of seismic activity, primarily:
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Strike-Slip Faulting: The most common type of fault at transform boundaries. In this scenario, the two plates move laterally past each other without much vertical movement. This can produce significant earthquakes along strike-slip faults.
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Earthquakes: The friction between the sliding plates can cause stress to build up over time. When the stress exceeds the strength of the rocks, it results in an earthquake. These earthquakes can vary in magnitude, and while many are small, large and damaging earthquakes can also occur.
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Aftershocks: Following a major earthquake along a transform boundary, smaller earthquakes known as aftershocks may occur as the crust adjusts to the new stress distribution.
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Foreshocks: These are smaller earthquakes that can precede a larger event, potentially indicating that a significant earthquake is about to occur, although they are not always present.
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Tremors: Continuous or periodic small seismic events can occur due to the constant movement of the tectonic plates at transform boundaries.
In summary, the primary type of seismic activity at transform boundaries is related to strike-slip faulting, resulting in earthquakes that can vary in frequency and intensity. Examples of well-known transform boundaries include the San Andreas Fault in California and the North Anatolian Fault in Turkey.