Modulation of high-frequency seismic noise by tidal deformations: The features of the phenomenon before strong earthquakes and a probable physical mechanism

2011 ◽  
Vol 47 (11) ◽  
pp. 951-965 ◽  
Author(s):  
V. Yu. Zaitsev ◽  
V. A. Saltykov ◽  
L. A. Matveev
1991 ◽  
Vol 81 (4) ◽  
pp. 1101-1114
Author(s):  
Jerry A. Carter ◽  
Noel Barstow ◽  
Paul W. Pomeroy ◽  
Eric P. Chael ◽  
Patrick J. Leahy

Abstract Evidence is presented supporting the view that high-frequency seismic noise decreases with increased depth. Noise amplitudes are higher near the free surface where surface-wave noise, cultural noise, and natural (wind-induced) noise predominate. Data were gathered at a hard-rock site in the northwestern Adirondack lowlands of northern New York. Between 15- and 40-Hz noise levels at this site are more than 10 dB less at 945-m depth than they are at the surface, and from 40 to 100 Hz the difference is more than 20 dB. In addition, time variability of the spectra is shown to be greater at the surface than at either 335- or 945-m depths. Part of the difference between the surface and subsurface noise variability may be related to wind-induced noise. Coherency measurements between orthogonal components of motion show high-frequency seismic noise is more highly organized at the surface than it is at depth. Coherency measurements between the same component of motion at different vertical offsets show a strong low-frequency coherence at least up to 945-m vertical offsets. As the vertical offset decreases, the frequency band of high coherence increases.


2009 ◽  
Vol 36 (9) ◽  
Author(s):  
Jian Zhang ◽  
Peter Gerstoft ◽  
Peter M. Shearer

Open Physics ◽  
2007 ◽  
Vol 5 (4) ◽  
Author(s):  
Gabriel Török ◽  
Zdeněk Stuchlík ◽  
Pavel Bakala

AbstractIn a series of papers it was discussed,on the basis of phenomenological arguments, whether the high frequency quasiperiodic oscillations (kHz QPOs)observed in the neutron-star and black-hole X-ray sources originate in the same physical mechanism. Recently it was suggested that a general trend seen in neutron star kHz QPOs instead excludes such a uniform origin. Using the example of the atoll source 4U 1636-53 we illustrate that this is not neccesarily true.


Author(s):  
Л.И. Морозова ◽  
А.В. Николаев ◽  
С.А. Пулинец

В работе делается попытка обобщить результаты наблюдений еще до конца не понятого явления, обычно называемого «линейные облачные аномалии» (ЛОА), наблюдае- мого над областями подготовки сильных землетрясений или интенсификации тектонической активности. В англоязычной литературе можно найти более лаконичное называние «earthquakeclouds». Несмотря на достаточно богатую литературу по этому вопросу, до сих пор остается не выясненной физическая при- рода ЛОА. Цель работы. Именно выяснения физического механизма формирования ЛОА перед землетря- сениями приставляет собой наиболее актуальную задачу. В данной работе мы делаем шаг впередв данном направлении, потому что основной целью нашего исследования является поиск источников формирова- ния ЛОА. Методы исследования. Нами получены экспериментальные доказательства, что ЛОА всех типов имеют зародышевые структуры в нижней атмосфере на уровне порядка 100 м от поверхности Земли, что доказывает связь генезиса ЛОА с процессами, инициируемыми в земной коре. Источником информации, используемой для проверки процессов формирования ЛОА, являются метеорологические данные, полу- чаемые из ассимилятивной модели GEOSFP, получаемые вблизи поверхности земли. Результаты работы. Сделана попытка проследить генезис ЛОА от поверхности земли до уровня сформировавшейся облач- ной структуры, и предложен физический механизм генерации ЛОА, в том числе поддержания их геоме- трической линейности в условиях турбулентной атмосферы. Данная работа была задумана совместно с ушедшим от нас А. В. Николаевым, мы постараемся включить в работу всё, что обсуждалось с ним при её подготовке, в том числе с учетом его принципиального мнения, что «неясность физических принципов не может быть причиной недоверия к экспериментальным результатам». Ключевые слова: линейные облачные аномалии, землетрясение, облачная гряда, прогноз землетря- сений An attempt is made in present paper to generalize the results of observations of the not yet fully understood phenomenon, usually called “linear cloud anomalies” (LCA), observed over the areas of impending strong earthquakes or intensification of tectonic activity. In the English-language literature, you can find a more concise name “earthquake clouds”. Despite the fairly rich literature on this issue, the physical nature of LСA remains unclear. Aim. It is the identificationof the physical mechanism of the formation of LCA before earthquakes that is the most urgent problem. In this work, we take a step forward in this direction, because the main aim of our study is to find the sources for the formation of LCA. Methods. We have obtained experimental evidence that LCA of all types have embryonic structures in the lower atmosphere at a level of about 100 m from the Earth’s surface, which proves the connection between the LCA genesis and the processes initiated in the earth’s crust. The source of information used to verify the formation of LCA is the meteorological data obtained near the earth’s surface from the assimilative model GEOS FP. Results. An attempt is made to trace the genesis of LСA from the earth’s surface to the level of the formed cloud structure, and a physical mechanism for the generation of LСA is proposed, including maintaining their geometric linearity under conditions of a turbulent atmosphere. This work was conceived together with A. V. Nikolaev, we will try to include in the work everything that was discussed with him during its preparation, including his principled opinion that “the lack of clarity of physical principles cannot be the reason for distrust of experimental results


1972 ◽  
Vol 62 (1) ◽  
pp. 13-29 ◽  
Author(s):  
H. M. Iyer ◽  
John H. Healy

Abstract The approximate hexagonal configuration of LASA subarrays enables their use as omnidirectional arrays. This property is used to study the phase velocity of short-period seismic noise at different frequencies. It is found that the noise in the low-frequency band consists mainly of surface waves traveling with average velocities in the range 3.0 to 3.5 km/sec. The high-frequency noise, in the band 0.45 to 1.0 Hz, has an average velocity of about 6.0 km/sec. It is quite likely that the high-frequency noise has the nature of locally-generated body waves. Statistical analysis of Pg velocities observed during a crustal refraction experiment at LASA lends support to this hypothesis.


1990 ◽  
Vol 63 (3-4) ◽  
pp. 151-162 ◽  
Author(s):  
B.P. Diakonov ◽  
B.S. Karryev ◽  
O.B. Khavroshkin ◽  
A.V. Nikolaev ◽  
L.N. Rykunov ◽  
...  

1992 ◽  
Vol 71 (1-2) ◽  
pp. 1-5 ◽  
Author(s):  
E.I. Gordeev ◽  
V.A. Saltykov ◽  
V.I. Sinitsin ◽  
V.N. Chebrov

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