Earthquake Recorded by Microbarographs

Heinrich, Ross R.

doi:10.1785/gssrl.21.3.23

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“…Since these short-period microseisms are apparently recorded quite often by instruments-4 such divergent construction and instrumental constants as short period Benioff s, Wood-Anderson Sprengnethers, and instruments of individual design at many widely scattered stations, it appears that these recorded oscillations are not due to mere instrumental difficulties. Considerations ci the relative insensivity of the Macelwane microbarograph to seismic disturbances [HEINRICH, 1950] and the dissimilarities in period, waveform, and group form between the ordinarily recorded microseisms and atmospheric micro-oscillations indicate that these disturbances, correlated is time, are not atmospheric micro-oscillations recorded on seismographs or microseisms records on microbarographs. This then seems to be a time correlation between true ground oscillations and true atmospheric oscillations recorded at the same place.…”

Section: Case Historiesmentioning

confidence: 98%

“…The establishment of their surf ace-wave eta" acter, or indeed their traveling-wave character, is a matter best resolved by the matched, high magnification instruments of the tripartite arrangement [MACELWANE, 1948]. Possibly, solution of this problem may be found in a phenomenon similar to those suggested by SEZAWA and KAHAI [1939], by HASKELL [1951], or by JARDETZKY andPRESS [1951].…”

Section: Case Historiesmentioning

confidence: 98%

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An observational study of the origin of short‐period microseisms near Saint Louis, Missouri

Walsh¹

1955

Eos Trans. AGU

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A survey of four years' records of Florissant Wood‐Anderson seismographs reveals that the very small, regular, group microseisms of period very near to 0.3 sec occur in storms of quite variable duration, from less than one hour to over 40 hours. By a consideration of gross hourly occurrences, times of storm beginning and ending and of maximum trace displacements, as well as an investigation of many individual cases, a distinct correlation in time is shown to exist between these short‐period microseisms at Florissant and increased short‐period microbarographic activity recorded by the Macelwane instrument at the same station. From only the six‐hourly surface synoptic maps, it appears that the great majority of the 155 arbitrarily chosen microseismic storms may be associated either with the approach or passage at the station of a cold frontal type discontinuity or both, or with local, non‐frontal convective activity. These relationships, in agreement with findings for the correlated microbarographic oscillations, suggest that local atmospheric turbulence may be a prime factor in the generation of these short period microseisms. Although this microseismic activity usually persists longer in the post‐ than in the pre‐cold frontal period, a study of these microseisms may be useful in predicting cold front passages over land. A few case histories are presented to reveal certain details of the synoptic study, particularity the sequence of microseismic activity during frontal passages. There is some indication that these correlated short‐period microseisms and atmospheric micro‐oscillations are truly recorded vibrations of the ground and of the barometric pressure, respectively. That is to say it appears that the recorded oscillations are not the result of atmospheric micro‐oscillations operating directly on the seismometers or microseisms affecting the microbarographs. It seems also indicated that these ground and atmospheric vibrations are not related as cause and effect at some distance from the recording points. However, they may well proceed from a common source. This study suggests that, with more precise information, combined analyses of these microseisms and micro‐oscillations may be useful in elucidating the local turbulent nature of the atmosphere.

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Section: Case Historiesmentioning

confidence: 98%

Section: Case Historiesmentioning

confidence: 98%