Marsquake! — Brad Strickland

A Startling Discovery
The colony is racing to complete its deep drilling project on the shoulders of Olympus Mons to tap the underlying heat of Mars for power generation. When an unexpected underground cavity collapses, a devastating quake damages a number of the buildings in the colony, most vitally some of the greenhouses in which food is grown.
The scramble to repair and rebuild the greenhouses becomes critical, but their food source is nothing compared to what is found in some of the previously undiscovered lava tubes and caves that lead far below the Martian surface....