The Collaborative International Dictionary
Microseismic
Microseism \Mi"cro*seism\, n. [Micro- + Gr. ? an earthquake, fr. ? to shake.] A feeble earth tremor not directly perceptible, but detected only by means of specially constructed apparatus. -- Mi`cro*seis"mic, Mi`cro*seis"mic*al, a.
Wiktionary
microseismic
a. Describing any small seismic event that causes little or no damage or disturbance