Drilling itself creates no discernible ground movement as the drill bit is formed of three cones that turn and grind away at the rock so slowly that you can’t feel the movement.

When drilling reaches the fault zone, drilling mud will be lost in the fractures and can cause some microseismicity. After drilling has been completed a ‘testing phase’ is carried out. It is common for small micro-seismic events to be felt during this period. At United Downs seismicity was felt at a maximum ground velocity of 0.8mm/s. This is ten times less than the Cornwall Council regulations for daytime blasting at quarries and could never cause any damage to nearby buildings or infrastructure.

For more information on induced seismicity and how GEL manages the risk, please see the separate Seismicity FAQ and the animation on YouTube.