Fault line

According to the Tenth Doctor, the ghosts were "bleeding" through the fault lines, crossing from their world across the Void and into N-Space. (TV: Army of Ghosts)

According to the Trickster, the village of Foxgrove, which was situated on a fault line of the Web of time, making it a "weakpoint". This allowed him to break into N-Space from the limbo dimensions when Sarah Jane Smith saved her parents who were destined to die in 1951. The Trickster was ultimately banished when Sarah Jane's parents chose to meet their fates. (TV: The Temptation of Sarah Jane Smith)

In 2015, when a then unknown alien force froze all planes in the skies across the globe, Clara Oswald speculated with UNIT that they could be used in an attack by targeting fault lines' to cause earthquakes or tsunamis. (TV: The Magician's Apprentice)