Aftershocks are smaller earthquakes that occur in the same area after a larger seismic event, known as the mainshock. They can happen minutes, days, or even months after the initial quake and are caused by the Earth's crust adjusting to the changes in stress and strain from the mainshock. While aftershocks are usually less intense than the mainshock, they can still cause damage, especially in areas already affected. The frequency and magnitude of aftershocks typically decrease over time, but they can still pose risks to structures and people, making it important to remain cautious in the aftermath of a significant earthquake, such as those associated with the San Andreas Fault.