Estimation of horizontal-to-vertical spectral ratios (ellipticity) of Rayleigh waves from multistation active-seismic records

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. EN81-EN92 ◽  
Author(s):  
Binbin Mi ◽  
Yue Hu ◽  
Jianghai Xia ◽  
Laura Valentina Socco
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Spectral Ratio ◽  
Lateral Velocity ◽  
Mode Separation ◽  
Novel Approach ◽  
Single Station ◽  
Seismic Records ◽  
Hvsr Technique ◽  
Multicomponent Data

The horizontal-to-vertical spectral-ratio (HVSR) analysis of ambient noise recordings is a popular reconnaissance tool used worldwide for seismic microzonation and earthquake site characterization. We have expanded this single-station passive HVSR technique to active multicomponent data. We focus on the calculation of the HVSR of Rayleigh waves from active-seismic records. We separate different modes of Rayleigh waves in seismic dispersion spectra and then estimate the HVSR for the fundamental mode. The mode separation is implemented in the frequency-phase velocity ([Formula: see text]-[Formula: see text]) domain through the high-resolution linear Radon transformation. The estimated Rayleigh-wave HVSR curve after mode separation is consistent with the theoretical HVSR curve, which is computed by solving the Rayleigh-wave eigenproblem in the laterally homogeneous layered medium. We find that the HVSR peak and trough frequencies are very sensitive to velocity contrast and interface depth and that HVSR curves contain information on lateral velocity variations. Using synthetic and field data, we determine the validity of estimating active Rayleigh-wave HVSR after mode separation. Our approach can be a viable and more accurate alternative to the empirical HVSR analysis method and brings a novel approach for the analysis of active multicomponent seismic data.

Measurements of Rayleigh-wave phase velocities in Nevada: Implications for explosion sources and the Massachusetts Mountain earthquake

1982 ◽  
Vol 72 (4) ◽  
pp. 1329-1349
Author(s):  
H. J. Patton
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Moment Tensor ◽  
Test Site ◽  
P Wave ◽  
Stress Axis ◽  
Phase Velocities ◽  
Wave Phase ◽  
Single Station ◽  
Source Phase

abstract Single-station measurements of Rayleigh-wave phase velocity are obtained for paths between the Nevada Test Site and the Livermore broadband regional stations. Nuclear underground explosions detonated in Yucca Valley were the sources of the Rayleigh waves. The source phase φs required by the single-station method is calculated for an explosion source by assuming a spherically symmetric point source with step-function time dependence. The phase velocities are used to analyze the Rayleigh waves of the Massachusetts Mountain earthquake of 5 August 1971. Measured values of source phase for this earthquake are consistent with the focal mechanism determined from P-wave first-motion data (Fischer et al., 1972). A moment-tensor inversion of the Rayleigh-wave spectra for a 3-km-deep source gives a horizontal, least-compressive stress axis oriented N63°W and a seismic moment of 5.5 × 1022 dyne-cm. The general agreement between the results of the P-wave study of Fischer et al. (1972) and this study supports the measurements of phase velocities and, in turn, the explosion source model used to calculate φs.

Analysis of Influencing Factors and Numerical Simulation of Horizontal-to-Vertical Spectral Ratio Method

2019 ◽  
Vol 14 (01) ◽  
pp. 2050004
Author(s):  
Du Qingling ◽  
Liu Zhengping ◽  
Liu Shijie
Keyword(s):  
Numerical Simulation ◽  
Rayleigh Wave ◽  
Influencing Factors ◽  
Phase Difference ◽  
Rayleigh Waves ◽  
Body Wave ◽  
Spectral Ratio ◽  
The Body ◽  
Hvsr Method ◽  
Different Sources

To improve the calculation accuracy of the horizontal-to-vertical spectral ratio (HVSR) method, this study theoretically analyzed the influencing factors of Rayleigh wave polarizability. The phase difference of the horizontal component and the phase difference of the vertical component are found to play a key role in calculating the polarizability. The influence mechanism of the superposition of body waves and different Rayleigh waves on the polarizability of the Rayleigh wave is derived. The effects of the body wave, amplitude, frequency and Rayleigh wave superposition of different sources on the polarizability are verified by numerical simulation. The results show that the body wave significantly interferes with the polarizability of the Rayleigh wave. When a signal contains more than one set of Rayleigh waves, the superposition of the same-source Rayleigh waves does not affect the ratio. However, the superposition of Rayleigh waves from different sources significantly interferes with the calculation of the polarizability. This provides a technical method and a theoretical basis for accurately extracting the Rayleigh wave polarizability dispersion curve from a seismic record signal. This would help improve the detection accuracy of the HVSR method for ground pulse signals.

scholarly journals Comparison of site effect values obtained by HVSR and HVSRN methods for single-station measurements in Tarnówek, South-Western Poland.

2016 ◽  
Vol 5 (1) ◽  
pp. 18-27 ◽  
Author(s):  
Maciej J. Mendecki ◽  
Barbara Bieta ◽  
Mateusz Mateuszów ◽  
Paweł Suszka
Keyword(s):  
Love Wave ◽  
Seismic Waves ◽  
Seismic Station ◽  
Spectral Ratio ◽  
Site Effect ◽  
Single Station ◽  
Subsurface Layers ◽  
Loose Sediments ◽  
Hvsr Technique ◽  
The Village

Abstract This study compares the HVSR technique (Horizontal to Vertical Spectral Ratio), based on seismic event records, and the HVSRN technique (Horizontal to Vertical Spectral Ratio of Noise) using seismic noise registrations. Both methods allow us to study the amplification phenomenon of a horizontal component of seismic waves when the waves reach loose sediments in subsurface layers. The seismic data were measured at a three-component single seismic station located in the village of Tarnówek, in the Legnica-Głogów Copper District. The results of the study demonstrate that average HVSRN and HVSR maxima can be distinguished: for periods approximately 3.78 s (H/V = 6.2) and 3.969 s (H/V = 8.98) respectively. The evaluated share of the Rayleigh wave component in the recorded values was β = 0.58 and it can be suggested that the Love wave share in surface motion was insignificant. The Love wave share remains unknown.

Rayleigh wave ellipticity in seismic noise studies based on vector random decrement technique (VRD)

2021 ◽  
Author(s):  
Naimeh Sadat Moghadasi ◽  
Elham Shabani
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Seismic Noise ◽  
Energy Content ◽  
Joint Inversion ◽  
Peak Frequency ◽  
Array Data ◽  
Random Decrement Technique ◽  
Random Decrement ◽  
Single Station

<p>In seismic hazard assessment studies, the estimation of site effects plays an important role. In recent years, using seismic noise has become increasingly popular because of their simplicity, low cost, and non-destructively. Seismic ambient noise wavefield investigation can be fulfilled by both single-station and array methods. The RayDec single station method is used to estimate ellipticity curve of Rayleigh wave based on Random Decrement (RD) technique by putting more emphasis on Rayleigh waves in compare to other participant waves in the seismic noise wavefield. In this study, to assess measuring the ellipticity of Rayleigh waves in an array of stations, Vector Random Decrement (VRD) technique is applied. The main idea is applying vector triggering condition on vertical components in an array of stations and selecting common triggering points. Those parts of signals where common points of all stations are detected would be included in further processing. It may lead to a lower number of obtained triggering points and insufficient convergence. To control the convergence, the vector of triggering conditions could be divided into some subsets. The maximum number of subsets can be estimated as the lowest integer of N/2 in which N is the number of stations in the array. Wherever, the common triggering points are detected on three components of the stations, the time windows with the same length are extracted. In the following, the signals in the mentioned windows are stacked and the ellipticity ratio is estimated by analyzing the energy content of the horizontal and vertical signals. In order to verify the method, synthetic circular array data are simulated using the FD code including five stations regularly placed on the circumference and a station in the center. Furthemore, the real array data recorded in Ramsar site (North of Iran) are used to study the method. The data included six Nanometrics trillium 40 seismic stations in which five stations placed on the circumference as well as a station at the center regarding to array aperture of about 15m. The retrieved ellipticity curves are evaluated and compared with the results of high resolution Rayleigh three component beam-forming (RTBF) method. The RTBF and VRD methods show good performance in recognizing the right flank of peak frequency while, the peak frequency and the left flank are better retrived using VRD method. Finally, the retrieved ellipticity curve from VRD alongside with the dispersion curves obtained from RTBF for both synthetic and real array data are used as targets in a joint inversion process to validate the shear wave velocity profile.</p>

Quantification of Effects of Ridge and Valley Topography on the Rayleigh Wave Characteristics

2018 ◽  
Vol 12 (03) ◽  
pp. 1850007 ◽  
Author(s):  
J. P. Narayan ◽  
A. Kumar
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Large Scale ◽  
Research Work ◽  
Vertical Component ◽  
Staggered Grid ◽  
Long Span ◽  
Shape Ratio ◽  
Day By Day ◽  
Ridge And Valley

The effects of ridge and valley on the characteristics of Rayleigh waves are presented in this paper. The research work carried out has been stimulated by the day by day increase of long-span structures in the hilly areas which are largely affected by the spatial variability in ground motion caused by the high-frequency Rayleigh waves. The Rayleigh wave responses of the considered triangular and elliptical ridge and valley models were computed using a fourth-order accurate staggered-grid viscoelastic P-SV wave finite-difference (FD) program. The simulated results revealed very large amplification of the horizontal component and de-amplification of the vertical component of Rayleigh wave at the top of a triangular ridge and de-amplification of both the components at the base of the triangular valley. The observed amplification of both the components of Rayleigh wave in front of elliptical valley was larger than triangular valley models. A splitting of the Rayleigh wave wavelet was inferred after interaction with ridge and valley. It is concluded that the large-scale topography acts as a natural insulator for the surface waves and the insulating capacity of the valley is more than that of a ridge. This insulation phenomenon is arising due to the reflection, diffraction and splitting of the surface wave while moving across the topography. It is concluded that insulating potential of the topography for the Rayleigh waves largely depends on their shape and shape-ratio.

Characteristics of long-period microtremors and their applicability in exploration of deep sedimentary layers

1994 ◽  
Vol 84 (6) ◽  
pp. 1831-1841 ◽  
Author(s):  
Hiroaki Yamanaka ◽  
Masayuki Takemura ◽  
Hiroshi Ishida ◽  
Masanori Niwa
Keyword(s):  
Rayleigh Waves ◽  
Ground Motions ◽  
Spectral Ratio ◽  
Northwestern Part ◽  
Trial And Error ◽  
Sediment Thickness ◽  
Short Term ◽  
Subsurface Structures ◽  
Long Period ◽  
Good Agreement

Abstract Applicability of long-period microtremors in inferring subsurface structure is examined using measurements of microtremors in the northwestern part of the Kanto Plain in Japan. Short-term continuous measurements of long-period microtremors at both sediment and basement sites were taken. A spectral peak at a period of 4 to 5 sec is stable with time, while peaks at periods less than 2 sec are time variant, suggesting a variation of microtremor sources. However, it was found that the spectral ratio between vertical and horizontal microtremors (ellipticity) at each site is stable with time. Good agreement was found between ellipticities of microtremors at the sediment site and those computed for Rayleigh waves in which the structure of the sediments beneath the site was taken into account. We also found that the ellipticities of Rayleigh waves in earthquake ground motions were consistent with those of the microtremors. These comparisons provide strong evidence that long-period microtremors in the area studied consist mainly of Rayleigh waves. The ellipticity of microtremors was investigated by observing microtremors at temporary observation sites in the Kanto Plain where the sediment thickness varied from 0 to 1 km. The subsurface structures were deduced by trial-and-error fitting of observed ellipticities with theoretical ellipticities that were calculated assuming Rayleigh waves. These results show that ellipticity of long-period microtremors is effective for deducing structure from microtremor data at a single site.

An algorithm for automated tsunami warning in French Polynesia based on mantle magnitudes

1989 ◽  
Vol 79 (4) ◽  
pp. 1177-1193
Author(s):  
Jacques Talandier ◽  
Emile A. Okal
Keyword(s):  
Rayleigh Wave ◽  
Seismic Moment ◽  
Rayleigh Waves ◽  
French Polynesia ◽  
Tsunami Warning ◽  
Period Range ◽  
Wave Duration ◽  
T Wave ◽  
The Moment ◽  
Historical References

Abstract We have developed a new magnitude scale, Mm, based on the measurement of mantle Rayleigh-wave energy in the 50 to 300 sec period range, and directly related to the seismic moment through Mm = log10M0 − 20. Measurements are taken on the first passage of Rayleigh waves, recorded on-scale on broadband instruments with adequate dynamical range. This allows estimation of the moment of an event within minutes of the arrival of the Rayleigh wave, and with a standard deviation of ±0.2 magnitude units. In turn, the knowledge of the seismic moment allows computation of an estimate of the high-seas amplitude of a range of expectable tsunami heights. The latter, combined with complementary data from T-wave duration and historical references, have been integrated into an automated procedure of tsunami warning by the Centre Polynésien de Prévention des Tsunamis (CPPT), in Papeete, Tahiti.

Rayleigh waves from high-gain long-period stations: Signal extraction, amplitude determination, and separation of overlapping wave trains

1975 ◽  
Vol 65 (6) ◽  
pp. 1761-1778 ◽  
Author(s):  
Eduard Berg
Keyword(s):  
Rayleigh Waves ◽  
Signal To Noise Ratio ◽  
High Gain ◽  
Clear Separation ◽  
Novaya Zemlya ◽  
Oceanic Surface ◽  
Single Station ◽  
Wave Trains ◽  
Short Time

abstract For a signal-to-noise ratio between 0.2 and 0.1 on the original single-component records, amplitudes for Rayleigh waves over oceanic paths of 155° at station MAT and 98° at station KIP have been determined as 12 mμ and 24 mμ peak-to-peak, respectively, with a standard error of less than 11 per cent. In each case the processed correlation signal is the highest in a half-hour record. The method makes use of preliminary high-pass filtering and normalized reference earthquake-matched filtering, and takes full advantage of the well-dispersed oceanic surface wave. The method also provides high resolution of co-located events with short time separation, or of widely spaced events with Rayleigh waves arriving nearly simultaneously at a single station, when the summed vertical and radial matched filtered components are used. Examples include: (1) clear separation and amplitude determination at stations KIP and MAT of two MS = 6.5 earthquakes located 0.7° and 145 sec apart off the coast of central Chile; (2) clear separation at station KIP of a Novaya Zemlya mb = 4.8 event from interfering Rayleigh waves of an mb = 5.0 Kermadec Island earthquake arriving 120 to 140 sec prior to the searched event, with almost complete elimination of interference on the summed vertical and radial processed components; and (3) clear separation at station KIP of two co-located mb = 4.4 and 4.5 earthquakes 6 min apart off the coast of Chile, with determination of their amplitudes in the presence of interfering Rayleigh waves from two central Alaska earthquakes, the first (mb = 4.1) arriving 15 min prior to the first Chile Rayleigh wave and the second between the two Chile arrivals. The single-station threshold reached (10 and 25 digital units, p-p) for stations MAT and KIP at 155° and 98°, respectively, corresponds to an MS = 3.3 and probably can be improved further.

Use of reciprocity theorem for obtaining Rayleigh wave radiation patterns

1966 ◽  
Vol 56 (4) ◽  
pp. 925-936 ◽  
Author(s):  
I. N. Gupta
Keyword(s):  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Three Dimensional ◽  
Reciprocity Theorem ◽  
Point Sources ◽  
Dimensional Case ◽  
Wave Radiation ◽  
Radiation Patterns ◽  
Homogeneous Half Space ◽  
Double Couple

abstract The reciprocity theorem is used to obtain Rayleigh wave radiation patterns from sources on the surface of or within an elastic semi-infinite medium. Nine elementary line sources first considered are: horizontal and vertical forces, horizontal and vertical double forces without moment, horizontal and vertical single couples, center of dilatation (two dimensional case), center of rotation, and double couple without moment. The results are extended to the three dimensional case of similar point sources in a homogeneous half space. Haskell's results for the radiation patterns of Rayleigh waves from a fault of arbitrary dip and direction of motion are reproduced in a much simpler manner. Numerical results on the effect of the depth of these sources on the Rayleigh wave amplitudes are shown for a solid having Poisson's ratio of 0.25.

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