Biological high‐frequency ambient noise

1998 ◽  
Vol 104 (3) ◽  
pp. 1826-1826
Author(s):  
Michael C. Macaulay
Keyword(s):  
High Frequency ◽  
Ambient Noise

Seismic imaging at a mineral-deposit scale using high-frequency surface waves (0.5–24 Hz) in ambient noise wavefield

2020 ◽  
Author(s):  
Y. Xu ◽  
S. Lebedev ◽  
R. Bonadio ◽  
T. Meier ◽  
C. Bean ◽  
...  
Keyword(s):  
Surface Waves ◽  
High Frequency ◽  
Ambient Noise ◽  
Seismic Imaging ◽  
Mineral Deposit

Near-surface Structure of Downtown Jinan, China: Application of Ambient Noise Tomography with a Dense Seismic Array

2019 ◽  
Vol 24 (4) ◽  
pp. 641-652
Author(s):  
Feng Liang ◽  
Zhihui Wang ◽  
Hailong Li ◽  
Kai Liu ◽  
Tao Wang
Keyword(s):  
Surface Wave ◽  
Human Activities ◽  
High Frequency ◽  
Urban Areas ◽  
Ambient Noise ◽  
Velocity Structure ◽  
Shear Velocity ◽  
Ambient Noise Tomography ◽  
Surface Wave Dispersion ◽  
Near Surface

Urban geophysics ups the ante in the world of applied geophysics, which requires innovative thinking and seemingly off-the-wall approaches, if for no other reason than the settings. Ambient-noise-tomography (ANT) can play a pivotal role in yielding subsurfa2ce information in urban areas, which is capable of dealing with challenges related to these scenarios ( e.g., human activities and low signal-to-noise ratio). In this study, the ANT was conducted to investigate the near-surface shear-velocity structure in the surrounding area of the Baotu Spring Park in downtown Jinan, Shandong Province, China. Quiet clear Rayleigh waves have been obtained by the cross-correlation, which indicates that strong human activities, such as moving vehicles and municipal engineering constructions, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surface-wave tomographic method with period-dependent ray-tracing was used to invert all surface-wave dispersion data in the period band 0.2-1.5 s simultaneously for 3D variations of shear-velocity (Vs) structure. Our results show a good correspondence to the geological features with thinner Quaternary sediments, the geological structural characteristic of the limestone surrounded by the igneous which has the highest velocity than that of the limestone in the study area, and several concealed faults of which specific location has been detected at depth. The results demonstrate that it is possible to successfully use ANT with high-frequency signal in an urban environment provided a detailed planning and execution is implemented.

Effects of Noise Frequency on Performance and Annoyance for Women and Men

1981 ◽  
Vol 52 (2) ◽  
pp. 435-441 ◽  
Author(s):  
Kelli F. Key ◽  
M. Carr Payne
Keyword(s):  
Sex Differences ◽  
Magnitude Estimation ◽  
High Frequency ◽  
Ambient Noise ◽  
Direct Relationship ◽  
Low Frequency ◽  
Frequency Noise ◽  
Complex Task ◽  
High Frequency Noise ◽  
Noise Frequency

Effects of noise frequencies on both performance on a complex psychomotor task and annoyance were investigated for men ( n = 30) and women ( n = 30). Each subject performed a complex psychomotor task for 50 min. in the presence of low frequency noise, high frequency noise, or ambient noise. Women and men learned the task at different rates. Little effect of noise was shown. Annoyance ratings were subsequently obtained from each subject for noises of various frequencies by the method of magnitude estimation. High frequency noises were more annoying than low frequency noises regardless of sex and immediate prior exposure to noise. Sex differences in annoyance did not occur. No direct relationship between learning to perform a complex task while exposed to noise and annoyance by that noise was demonstrated.

High-frequency seismic interferometry: broadband measurements of surface-wave phase velocities using “large-N” arrays

2021 ◽  
Author(s):  
Yihe Xu ◽  
Sergei Lebedev ◽  
Raffaele Bonadio ◽  
Thomas Meier ◽  
Christopher Bean
Keyword(s):  
Surface Wave ◽  
Phase Velocity ◽  
High Frequency ◽  
Ambient Noise ◽  
Frequency Noise ◽  
Frequency Range ◽  
Velocity Measurements ◽  
Phase Velocities ◽  
Wave Phase ◽  
Large N

<p>High-frequency seismic surface waves sample the top few tens of meters to the top few kilometres of the subsurface. They can be used to determine three-dimensional distributions of shear-wave velocities and to map the depths of discontinuities (interfaces) within the crust. Passive seismic imaging, using ambient noise as the source of signal, can thus be an effective tool of exploration for mineral, geothermal and other resources, provided that sufficient high-frequency signal is available in the ambient noise wavefield and that accurate, high-frequency measurements can be performed on this signal. Ambient noise imaging using the ocean-generated noise at 5-30 s periods is now a standard method, but less signal is available at frequencies high enough for deposit-scale imaging (0.2-30 Hz), and few studies have reported successful measurements in broad frequency bands. Here, we develop a workflow for the measurement of high-frequency, surface-wave phase velocities in very broad frequency ranges. Our workflow comprises (1) a new noise cross-correlation procedure that accounts for the non-stationary properties of the high frequency noise sources, removes bandpass filtering, replaces temporal normalization with short time window stacking, and drops the explicit spectral normalization by adopting cross-coherence; (2) a new phase-velocity measurement method that extends the bandwidth of reliable measurements by exploiting the (resolved) 2π ambiguity of phase-velocity measurements; (3) interstation-distance-dependent quality control that uses the similarity of subgroups of dispersion curves to reject outliers and identify the frequency ranges with accurate measurements. The workflow is highly automated and applicable to large arrays. Applying our method to data from a large-N array that operated for one month near Marathon, Ontario, Canada, we use rectangular subarrays with 150-m station spacing and, typically, 1 hour of data and obtain Rayleigh-wave phase-velocity measurements in a 0.55-23.8 Hz frequency range, spanning over 5.4 octaves, nearly twice the typical frequency range of 1.5-3 octaves in previous studies. Phase-velocity maps and the subregion-average 1D velocity models they constrain show a high-velocity anomaly consistent with the known, west-dipping gabbro intrusions beneath the area. The new structural information can improve our understanding of the geometry of the gabbro intrusions, hosting the Cu-PGE Marathon deposit.</p>

Observation of high‐frequency ambient noise generated by capillary waves

1990 ◽  
Vol 87 (S1) ◽  
pp. S111-S111
Author(s):  
Ali Kolaini ◽  
Ronald A. Roy ◽  
Lawrence A. Crum
Keyword(s):  
High Frequency ◽  
Ambient Noise ◽  
Capillary Waves

Seismic Magnitudes, Corner Frequencies, and Microseismicity: Using Ambient Noise to Correct for High-Frequency Attenuation

2020 ◽  
Vol 110 (3) ◽  
pp. 1260-1275 ◽  
Author(s):  
Antony Butcher ◽  
Richard Luckett ◽  
J.-Michael Kendall ◽  
Brian Baptie
Keyword(s):  
Stress Drop ◽  
High Frequency ◽  
Seismic Noise ◽  
Seismic Risk ◽  
Ambient Noise ◽  
Source Model ◽  
Lower Stress ◽  
Microseismic Activity ◽  
Stress Drops ◽  
Seismic Catalog

ABSTRACT Over recent years, a greater importance has been attached to low-magnitude events, with increasing use of the subsurface for industrial activities such as hydraulic fracturing and enhanced geothermal schemes. Magnitude distributions and earthquake source properties are critical inputs when managing the associated seismic risk of these activities, yet inconsistencies and discrepancies are commonly observed with microseismic activity (M<2). This, in part, is due to their impulse response being controlled by the medium, as opposed to the source. Here, an approach for estimating the high-frequency amplitude decay parameter from the spectral decay of ambient seismic noise (κ0_noise) is developed. The estimate does not require a pre-existing seismic catalog and is independent of the source properties, so avoids some of the main limitations of earthquake-based methods. We then incorporate κ0_noise into the Brune (1970) source model and calculate source properties and magnitude relationships for coal-mining-related microseismic events, recorded near New Ollerton, United Kingdom. This generates rupture radii ranging approximately between 10 and 100 m, which agrees with the findings of Verdon et al. (2018), and results in stress-drop values between 0.1 and 10 MPa. Calculating these properties without κ0_noise produces much higher rupture radii of between 100 and 500 m and significantly lower stress drops (∼1×10−2  MPa). Finally, we find that the combined κ0-Brune model parameterized with these source property estimates accurately capture the ML–Mw relationship at New Ollerton, and that stress drop heavily influences the gradient of this relationship.

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