Mid‐ocean microseisms

Bromirski, Peter D.; Duennebier, F. K.; Stephen, Ralph A.

doi:10.1029/2004gc000768

Cited by 177 publications

(211 citation statements)

References 25 publications

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“…We stated, after various attempts, that microseisms have an annual drift, which is explained mainly by annual variations of meteorological conditions, especially wind speed over the sea (Bromirski et al 2005), sea wave height (in 2nd power are proportional with microseism amplitude) (Essen et al 2003;Stehly et al 2006), air pressure variations (Peters 2005), and coastal and sea ice conditions (Grob et al 2011). However, this annual drift could be explained by other influences, which have an annual period, such as temperature variations, differences of air pressure or temperature between various parts of the continent, etc.…”

Section: Analysis Of the Interaction Between Meteorological Conditionmentioning

confidence: 99%

Mutual Coupling Between Meteorological Parameters and Secondary Microseisms

Holub¹,

Kalenda²,

Rušajová³

2013

Terr. Atmos. Ocean. Sci.

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The basic scientific question of this study was: do other mechanisms exist for excitation of secondary microseisms aside from the widely accepted mechanism by non-linear interactions of respective ocean waves. Here we use continuous broadband data from secondary microseisms recorded at the Ostrava-Krásné Pole, Czech Republic (OKC) seismic station to create a massive seismological database. Except for seismological data, various meteorological features and their mutual relations were analysed: temperature, the so called "shifted" temperature, air density, changes of atmospheric pressure, and synoptic situations. These analyses prove that maximum amplitudes of microseisms were observed during winter, while minimum amplitudes occured in summer months. The annual variations of microseisms amplitudes could not be explained by annual variations of storm activity above the North Atlantic. In addition, current analyses also aim at quantitative and quantitative evaluation of synoptic situations for triggering individual microseismic anomalies. Some of the meteorological features, namely the distribution of low pressures above northern Europe and high-pressure areas in Central Europe make it easy to explain most of the microseismic extremes. Here we pay special attention to the influence of large earthquakes, which usually induce slow deformation waves. We conclude that at least three mechanisms of microseism generation are possible: (1) the function of atmospheric pressure at sea level in the North Atlantic, (2) the effects of spreading of thermoelastic waves in the rock mass and (3) deformation waves induced by large earthquakes.

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Section: Analysis Of the Interaction Between Meteorological Conditionmentioning

confidence: 99%

Mutual Coupling Between Meteorological Parameters and Secondary Microseisms

Holub¹,

Kalenda²,

Rušajová³

2013

Terr. Atmos. Ocean. Sci.

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“…2a). This peak is referred to as LPDF in the literature (Long Period Double Frequency) (Bromirski et al, 2005;Koper and Buriaciu, 2015) and LPSM in the present paper. The spectrogram exhibits a clear peak in the SM band around 8 s, i.e., at twice the PM frequency, with the same slope than the PM energy, suggesting the presence of a SM source close to the island (likely on its southern side).…”

Section: Origins Of Microseismic Noisementioning

confidence: 97%

“…If incident and reflected waves propagate in opposite directions, the incoming swell may interfere with its reflected swell, resulting in the generation of standing waves in coastal areas, oscillating at twice the frequency of the propagating wave (Bromirski et al, 2005). Some observations suggest that local and distant sources of noise in the SM frequency peak may coexist (e.g., Chevrot et al, 2007;Koper and Buriaciu, 2015).…”

Section: Origins Of Microseismic Noisementioning

confidence: 99%

Monitoring austral and cyclonic swells in the “Iles Eparses” (Mozambique channel) from microseismic noise

et al. 2016

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a b s t r a c tWe deployed five broadband three-components seismic stations in the Iles Eparses in the south-west Indian Ocean and on Mayotte Island, between April 2011 and January 2014. These small and remote oceanic islands suffer the effects of strong ocean swells that affect their coastal environments but most islands are not instrumented by wave gauges to characterize the swells. However, wave action on the coast causes high levels of ground vibrations in the solid earth, so-called microseismic noise. We use this link between the solid earth and ocean wave activity to quantify the swells locally. Spectral analyses of the continuous seismic data show clear peaks in the 0.05e0.10 Hz frequency band (periods between 10 and 20 s), corresponding to the ocean wave periods of the local swells. We analyze an example of austral swell occurring in August 2013 and a cyclonic event (Felleng) that developed in January 2013, and quantify the ground motion at each station induced by these events. In both cases, we find a linear polarization in the horizontal plane with microseismic amplitude directly correlated to the swell height (as predicted by the global swell model WaveWatchIII), and a direction of polarization close to the predicted swell propagation direction. Although this analysis has not been performed in real time, it demonstrates that terrestrial seismic stations can be efficiently used as wave gauges, and are particularly well suited for quantifying extreme swell events. This approach may therefore provide useful and cheaper alternatives to wave buoys for monitoring swells and the related environmental processes such as beach erosion or coral reef damages.

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“…Bromirski et al (2005) pointed out a distinction between microseisms having peaks around 0.15 Hz, which can travel with low attenuation over very long distances, and those having peaks at frequencies between 0.2 and 0.3 Hz, which are much more attenuated and observed only in coastal areas relatively near the source. At frequencies larger than 0.3 Hz microseismic energy does not seem to propagate through the ocean floor beyond a few hundreds of km, and signals observed at these frequencies are generally excited by windgenerated local waves.…”

Section: Del Gaudio Et Al: New Developments In Ambient Noise Analmentioning

confidence: 99%

New developments in ambient noise analysis to characterise the seismic response of landslide-prone slopes

Gaudio

Wąsowski

Muscillo

2013

Nat. Hazards Earth Syst. Sci.

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We report on new developments in the application of ambient noise analysis applied to investigate the dynamic response of landslide-prone slopes to seismic shaking, with special attention to the directional resonance phenomena recognised in previous studies. These phenomena can be relevant for seismic slope susceptibility, especially when maximum resonance orientation is close to potential sliding directions. Therefore, the implementation of an effective technique for site response directivity detection is of general interest. In this regard methods based on the calculation of horizontal-to-vertical noise spectral ratio (HVNR) are promising. The applicability of such methods is investigated in the area of Caramanico Terme (central Italy), where ongoing accelerometer monitoring of slopes with different characteristics offers the possibility of validation of HVNR analysis. The noise measurements, carried out in different times to test the result repeatability, revealed that sites affected by response directivity persistently show major peaks with a common orientation, consistent with the resonance direction inferred from accelerometer data. In some cases such a directivity turned out parallel to maximum slope direction, but this cannot be considered a systematic feature of slope dynamic response. At sites where directivity is absent, the HVNR peaks do not generally show a preferential orientation, with rare exceptions that could be linked to the presence of temporarily active sources of polarised noise. The observed variations of spectral ratio amplitude can be related to temporal changes in site conditions (e.g. groundwater level/soil water content variations affecting P wave velocity and Poisson's ratio of surficial layer), which can hinder the recognition of main resonance frequencies. Therefore, we recommend conducting simultaneous measurements at nearby sites within the same study area and repeating measurements at different times in order to distinguish significant systematic polarisation caused by site-specific response directivity from polarisation controlled by properties of noise sources. Furthermore, an analysis of persistence in noise recordings of signals with systematic directivity showed that only a portion of recordings contains wave trains having a clear polarisation representative of site directional resonance. Thus a careful selection of signals for HVNR analysis is needed for a correct characterisation of site directional properties

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Mid‐ocean microseisms

Cited by 177 publications

References 25 publications

Mutual Coupling Between Meteorological Parameters and Secondary Microseisms

Mutual Coupling Between Meteorological Parameters and Secondary Microseisms

Monitoring austral and cyclonic swells in the “Iles Eparses” (Mozambique channel) from microseismic noise

New developments in ambient noise analysis to characterise the seismic response of landslide-prone slopes

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