| 释义 |
microseism|maɪkrəʊˈsaɪz(ə)m|
[f. Gr. µῑκρό-ς small + σεισµός shaking, earthquake.]
A minor earthquake; in mod. use, any imperceptible disturbance of the earth's crust which is capable of being registered on a sensitive seismometer but which is not caused by an earthquake (see quots.).
1887G. H. Darwin in Fortn. Rev. Feb. 271 Earth tremors or ‘microseisms’ are not confined to countries habitually visited by the grosser sort of earthquakes. 1888Times 24 Nov. 15/2 There may have been a succession of microseisms perceptible only to the delicate senses of quadrupeds and other dumb creatures. 1903[see macroseism]. 1924Bull. Seismol. Soc. Amer. XIV. 28 They [sc. earth-tremors] are now generally known as microseisms. 1959Observer 6 Sept. 4/8 Another advance is the linking of ‘microseisms’—minute earth tremors which constantly vibrate the recording pens of seismographs—with storms at sea. 1965A. Holmes Princ. Physical Geol. (rev. ed.) xxv. 916 As a background to the P, S and L waves and their many associates there are small irregular earth tremors and quiverings going on all the time... These microseisms..set a limit to the degree of magnification that can usefully be employed, since they only confuse the earthquake record if they are made too big. Some of the more conspicuous microseisms are caused by distant traffic, others by the pounding of breakers on rocky coasts, while others have been traced to changes of atmospheric pressure and especially to hurricanes and typhoons. But after all such regional increases of microseismic activity have been accounted for, there still remains a world-wide background of chaotic seismic ‘noise’. Don and Florence Leet have suggested that these microseisms are caused by the strained condition of the crust, which ‘hums’ or ‘sings’ like a highly strained piece of steel. 1971Nature 12 Feb. 452/3 Microseisms are of practical importance in predicting the onset of a storm in areas where meteorological observations are scarce. |