What is "microquakes"

Usage examples of "microquakes".

Something about the microquakes reminded her of the street rumbling as a subway train passed beneath her feet.

At first she had thought—or at least had hoped—that the microquakes were just the asteroid reaching a new equilibrium, a normal reaction to a most abnormal source of acceleration.

In all probability, the digital cognizance given off by a tiny info unit would be masked by the geysers and microquakes forever popping under the Rimmers.