Crisis memo elaborated minor earthquake

• A small earthquake

WordNet Word definitions in WordNet
n. a small earthquake [syn: tremor , earth tremor ]

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
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 Word definitions in Wiktionary
n. A faint earth tremor caused by natural phenomena, such as wind.

Wikipedia Word definitions in Wikipedia
In seismology , a microseism is defined as a faint earth tremor caused by natural phenomena. Sometimes referred to as a "hum", it should not be confused with the anomalous acoustic phenomenon of the same name . The term is most commonly used to refer to ...