微弱的地壳震动
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}]