In Quaking Hills by Kate MacLeod

After spending the last four days of her life hiding out from a deadly solar particle storm in an underground bunker, trapped with six treacherous women and a trio of girl assassins, Scout Shannon just wants to find the man who conned her mentor and leave her home world for good.

Alas, the long-threatened war draws nearer and Scout finds herself caught in the middle, surrounded by rebels and bandits. Worse, she carries a pocketful of dangerous secrets with no one to entrust them to.

And the hills keep shaking. Something lurks deep underground. Something massive. Something world-destroying. Scout leaves in three days. If she lives that long.

"In Quaking Hills", the sequel to "Under Falling Skies" and the second book in "The Travels of Scout Shannon" series, a young adult science fiction novel for fans of plucky heroines, complicated boys, and loyal dog sidekicks.