Final answer:
Earthquakes at conservative plate margins are caused by the buildup of stress from plates sliding past one another until it is released in a sudden and violent slip, with longer intervals between such events leading to more energy release during the earthquakes.
Step-by-step explanation:
Earthquakes occur at conservative plate margins when the motion along fault zones is not smooth. The plates engage in a creeping motion against each other, accumulating stress in the crust. This stress is eventually released in sudden, violent slippages that generate earthquakes. The energy release during an earthquake is related to the period since the last event: the longer the interval between earthquakes, the greater the accumulated stress, and consequently, the more energy is released during the next event.
The movement at conservative margins involves the horizontal sliding of plates past one another, which is typically a few centimeters per year. Faults, such as the San Andreas Fault, illustrate this process. The lack of smooth motion along these faults is due to roughness and irregularities between the sliding surfaces of the plates, leading to the buildup of strain until it's overcome by a seismic event.
No new crust is created or destroyed at conservative margins, unlike at divergent or convergent boundaries. Therefore, these earthquake events usually do not result in volcanic activity, as they occur without the subduction of one plate under another.