微气压波与地震
SOME RELATIONS BETWEEN MICROBAROMIC WAVES AND EARTHQUAKES
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摘要: 地震之前长周期的地壳运动已为人们所关注,然而在零漂等问题尚未解决之前,长周期地震仪观测仍处于试验性阶段.另外,震前地气的喷溢和释放,只能在喷口处观测,距离稍远,就观测不到了,但由此而引起的大气振动和声学现象,却可在一定距离范围内观测到.因而可开展震前由长周期运动和地气等引起的大气声波、重力波等微气压波的观测研究.地震波所激发的次声[1],前人已有研究,但地震前的次声,中外文献还未见报道.1976年唐山地震后的1976年8月至1977年3月,笔者在北京首次开展微气压波的观测,发现了十余次地震前的微气压波,其特征为40—80秒的周期,1—5微巴的声压,波列很短,仅数分钟,出现于震前1—16小时.本文提出了识别震前微压波的分析方法,并讨论了其产生的可能机制和有关的临震现象.Abstract: The long period crustal movement prior to earthquakes has been noticed for a long time. However, the problem of zerodrift of long period seismographs rendered the observations with such seismographs tentative or experimental in nature. Besides, when the underground gas spurts oat and sets free before earthquakes, the observation of such gas can be made only near it but not too far away. The microbaro-mic waves, such as infrasonic and gravity waves caused by the gas outspurts and long period ground movements prior to earthquakes may be detected at a distance, thus should be studied.Infrasound caused by seismic waves has been noticed long ago, but no report on infrasound before earthquakes has been made. After the 1976 Tangshan earthquake, from August 1976 to March 1977, the author observed microbaromic waves prior to aftershocks with microbarograph at Peking. More than ten of this kind of waves were observed. Its characteristics are as follows: the period is 40—80 seconds, sonic pressure 1—5μb(microbar), duration lasts a few minutes and it appeared 1—16 hours prior to the earthquakes.In this paper, a method of analysis for recognizing microbaromic waves prior to earthquakes is developed. Its possible mechanism and other phenomena have been discussed.
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