The Hammer of Eden

The Hammer of Eden is a work by Ken Follett published in 1998.
Plot.
It is about a group of people living together in a commune cut off from the rest of the world. When their commune is threatened by a plan to build a dam, they turn desperate and devise a devious plan to arm-twist the governor of California to abandon the project. They transform themselves into eco-terrorists and threaten to start an earthquake if their demands are not met. They set off a series of earthquakes using a stolen seismic vibrator truck from an oil firm. Their leader is an illiterate man called Priest who is helped by a seismology student called Melanie in his plans. Judy Maddox, an FBI agent, is the only one who can stop them and the rest of the story revolves around how she tries to do so.