First To Die — Peter Nelson

Seven teens trapped underground after an earthquake discover that the only person who knows their location is a criminal who would rather them dead.
 
For sixteen-year-old Mollie Fox, selling earthquake insurance is just a way to keep her beloved Jeep on the road. But when the Big One actually does strike California, Mollie finds herself living her worst nightmare. Trapped in a basement office beneath a collapsed shopping mall, Mollie makes two startling discoveries: The company she works for is a scam, and her crooked boss has left her and her six coworkers for dead. Between the dangerous aftershocks and the possibility of starving to death, Mollie and her friends are fighting for survival. The only thing keeping hope alive is the amount of criminal evidence they find in the wreckage -- enough to put their creepy employer behind bars for a very long time. That is, if they don't die first . . .