Assessment of the stability of H/V spectral ratios from ambient noise and comparison with earthquake data in the Cologne area (Germany)

2004 ◽  
Vol 390 (1-4) ◽  
pp. 57-73 ◽  
Author(s):  
Stefano Parolai ◽  
Sandra M. Richwalski ◽  
Claus Milkereit ◽  
Peter Bormann
Keyword(s):  
Ambient Noise ◽  
Spectral Ratios ◽  
The Stability ◽  
Earthquake Data

On the Stability and Reproducibility of the Horizontal-to-Vertical Spectral Ratios on Ambient Noise: Case Study of Cavola, Northern Italy

2010 ◽  
Vol 100 (3) ◽  
pp. 1263-1275 ◽  
Author(s):  
F. Cara ◽  
G. Di Giulio ◽  
G. Milana ◽  
P. Bordoni ◽  
J. Haines ◽  
...  
Keyword(s):  
Ambient Noise ◽  
Northern Italy ◽  
Spectral Ratios ◽  
The Stability

scholarly journals Investigating the Consistency of Uncalibrated Multispectral Lidar Vegetation Indices at Different Altitudes

2019 ◽  
Vol 11 (13) ◽  
pp. 1531 ◽  
Author(s):  
Maxim Okhrimenko ◽  
Chris Hopkinson
Keyword(s):  
Vegetation Indices ◽  
Atmospheric Correction ◽  
Spectral Ratios ◽  
Additional Information ◽  
Point Density ◽  
Range Difference ◽  
Spectral Vegetation Indices ◽  
The Stability ◽  
Considerable Range ◽  
Different Altitudes

Multi-spectral (ms) airborne light detection and ranging (lidar) data are increasingly used for mapping purposes. Geometric data are enriched by intensity digital numbers (DNs) and, by utilizing this additional information either directly, or in the form of active spectral vegetation indices (SVIs), enhancements in land cover classification and change monitoring are possible. In the case of SVIs, the indices should be calculated from reflectance values derived from intensity DNs after rigorous calibration. In practice, such calibration is often not possible, and SVIs calculated from intensity DNs are used. However, the consistency of such active ms lidar products is poorly understood. In this study, the authors reported on an ms lidar mission at three different altitudes above ground to investigate SVI consistency. The stability of two families of indices—spectral ratios and normalized differences—was compared. The need for atmospheric correction in case of considerable range difference was established. It was demonstrated that by selecting single returns (provided sufficient point density), it was possible to derive stable SVI products. Finally, a criterion was proposed for comparing different lidar acquisitions over vegetated areas.

scholarly journals Teleseismic correlations of ambient seismic noise for deep global imaging of the Earth

2013 ◽  
Vol 194 (2) ◽  
pp. 844-848 ◽  
Author(s):  
P. Boué ◽  
P. Poli ◽  
M. Campillo ◽  
H. Pedersen ◽  
X. Briand ◽  
...  
Keyword(s):  
Seismic Noise ◽  
Ambient Noise ◽  
Inner Core ◽  
Global Analysis ◽  
Imaging Study ◽  
Ambient Seismic Noise ◽  
Core Mantle Boundary ◽  
The Core ◽  
The Earth ◽  
Earthquake Data

Abstract We present here a global analysis showing that wave paths probing the deepest part of the Earth can be obtained from ambient noise records. Correlations of seismic noise recorded at sensors located various distances apart provide new virtual seismograms for paths that are not present in earthquake data. The main arrivals already known for earthquake data are also present in teleseismic correlations sections, including waves that have propagated through the Earth's core. We present examples of applications of such teleseismic correlations to lithospheric imaging, study of the core mantle boundary or of the anisotropy of the inner core.

Statistical correlation of earthquake and ambient noise spectral ratios

2014 ◽  
Author(s):  
Giovanna Cultrera ◽  
Valerio De Rubeis ◽  
Nikos Theodoulidis ◽  
Héloïse Cadet ◽  
Pierre-Yves Bard
Keyword(s):  
Ambient Noise ◽  
Statistical Correlation ◽  
Spectral Ratios

scholarly journals On the use of the coda of seismic noise autocorrelations to compute H/V spectral ratios

2019 ◽  
Vol 220 (3) ◽  
pp. 1956-1964 ◽  
Author(s):  
F N Tchawe ◽  
B Froment ◽  
M Campillo ◽  
L Margerin
Keyword(s):  
Ambient Noise ◽  
Sedimentary Basin ◽  
Temporal Stability ◽  
Spectral Ratio ◽  
Spectral Ratios ◽  
Data Set ◽  
Underlying Assumption ◽  
Seismic Ambient Noise ◽  
Physical Information ◽  
Local Medium

SUMMARY The horizontal to vertical spectral ratio (HVSR) of seismic ambient noise has been proven to be a fast and efficient method for characterizing the 1-D resonance frequency of the local subsurface in a practical framework. Over the last decades, theories have been developed in order to extend the exploitation of HVSR beside the frequency of its first peak, notably the diffuse field assumption (DFA) which links the HVSR to the Green’s function of the local medium assuming the diffuseness of the seismic ambient noise wavefield. However, the underlying assumption of the seismic ambient noise being a diffuse, equipartitioned field may not be satisfied under certain circumstances. In order to exploit the contribution of scattering in forging diffuse wave fields, we leverage the advantages of coda waves and present a novel procedure for computing the HVSR, using the coda part of ambient noise correlations. We applied this technique to data gathered at the plio-quaternary sedimentary basin of Argostoli, Greece. Results on this data set show the potential of the method to improve the temporal stability of the HVSR measurements compared to the classical computation, and the fit with the theoretical HVSR curve derived from the DFA theory. These results suggest that this procedure could help in extracting physical information from the HVSR and thus could lead to an extended use of these measurements to characterize the mechanical properties of the medium.

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