微弱的地殼震動
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}, {*seis"mic*al}, a.
microseism
n : a small earthquake [syn: {tremor}, {earth tremor}]