A new method for the analysis of multi-mode surface-wave dispersion: Application to Love-wave propagation in the east Pacific

1975 ◽  
Vol 65 (2) ◽  
pp. 323-342 ◽  
Author(s):  
Donald W. Forsyth
Keyword(s):  
Wave Propagation ◽  
Surface Wave ◽  
Phase Velocity ◽  
Love Wave ◽  
Wave Dispersion ◽  
Oceanic Lithosphere ◽  
Surface Wave Dispersion ◽  
Earthquake Sources ◽  
East Pacific ◽  
The Difference

abstract A new technique is presented for simultaneously measuring the average, regional phase velocity of two or more surface-wave modes, even if they travel with the same group velocity. Many observations are required over paths of varying length with earthquake sources of known focal mechanism. The phase of the signal observed at each station can be predicted if the initial phase of the source and the phase velocity and relative amplitude of each mode is known. The square of the difference between the observed phase and the predicted phase is summed over all paths for a set of trial phase velocities. The trial velocities which give the minimum sum correspond to the average phase velocity of each mode. By applying this technique to Love-wave data from the east Pacific, the dispersion of the first higher Love mode was measured for the first time in an oceanic area. The phase velocity of the fundamental mode was found to increase with increasing age of the sea floor, probably as a result of the cooling of the oceanic lithosphere. The region was found to be anisotropic for Love-wave propagation, with the fastest velocities roughly perpendicular to the ridge. The degree of anisotropy appears to increase with increasing period.

scholarly journals Oceanic lithosphere-asthenosphere boundary from surface wave dispersion data

2014 ◽  
Vol 119 (2) ◽  
pp. 1079-1093 ◽  
Author(s):  
G. Burgos ◽  
J.-P. Montagner ◽  
E. Beucler ◽  
Y. Capdeville ◽  
A. Mocquet ◽  
...  
Keyword(s):  
Surface Wave ◽  
Wave Dispersion ◽  
Oceanic Lithosphere ◽  
Surface Wave Dispersion ◽  
Dispersion Data

scholarly journals Accurate Sparse Recovery of Rayleigh Wave Characteristics Using Fast Analysis of Wave Speed (FAWS) Algorithm for Soft Soil Layers

2018 ◽  
Vol 8 (7) ◽  
pp. 1204
Author(s):  
Zhuoshi Chen ◽  
Baofeng Jiang ◽  
Jingjing Song ◽  
Wentao Wang
Keyword(s):  
Surface Wave ◽  
Phase Velocity ◽  
Dispersion Curve ◽  
Wave Speed ◽  
Soft Soil ◽  
Wave Dispersion ◽  
Surface Wave Dispersion ◽  
Fast Analysis ◽  
Soil Layers ◽  
Norm Minimization

This paper presents a novel fast analysis of wave speed (FAWS) algorithm from the waveforms recorded by a random-spaced geophone array based on a compressive sensing (CS) platform. Rayleigh-type seismic surface wave testing is excited by a hammer source and conducted to develop the phase velocity characteristics of the subsoil layers in Shenyang Metro line 9. Data are filtered by a bandpass filter bank to pursue the dispersive profiles of phase velocity at various frequencies. The Rayleigh-type surface-wave dispersion curve for the soil layers at each frequency is conducted by the ℓ1-norm minimization algorithm of CS theory. The traditional frequency-wavenumber transform technique and in-site downhole observation are employed as the comparison of the proposed technique. The experimental results indicate the proposed FAWS algorithm has a good agreement with both the results of conventional even-spaced geophone array and the in-site measurements, which provides an effective and efficient way for accurate non-destructive evaluation of the surface wave dispersion curve of the soil.

scholarly journals A MATLAB Package for Calculating Partial Derivatives of Surface-Wave Dispersion Curves by a Reduced Delta Matrix Method

2019 ◽  
Vol 9 (23) ◽  
pp. 5214 ◽  
Author(s):  
Wu ◽  
Wang ◽  
Su ◽  
Zhang
Keyword(s):  
Surface Wave ◽  
Group Velocity ◽  
Love Wave ◽  
Wave Dispersion ◽  
Dispersion Curves ◽  
Wave Group ◽  
Surface Wave Dispersion ◽  
Partial Derivatives ◽  
Matlab Package ◽  
Derivatives Of

Various surface-wave exploration methods have become increasingly important tools in investigating the properties of subsurface structures. Inversion of the experimental dispersion curves is generally an indispensable component of these methods. Accurate and reliable calculation of partial derivatives of surface-wave dispersion curves with respect to parameters of subsurface layers is critical to the success of these approaches if the linearized inversion strategies are adopted. Here we present an open-source MATLAB package, named SWPD (Surface Wave Partial Derivative), for modeling surface-wave (both Rayleigh- and Love-wave) dispersion curves (both phase and group velocity) and particularly for computing their partial derivatives with high precision. The package is able to compute partial derivatives of phase velocity and of Love-wave group velocity analytically based on the combined use of the reduced delta matrix theory and the implicit function theorem. For partial derivatives of Rayleigh-wave group velocity, a hemi-analytical method is presented, which analytically calculates all the first-order partial differentiations and approximates the mixed second-order partial differentiation term with a central difference scheme. We provide examples to demonstrate the effectiveness of this package, and demo scripts are also provided for users to reproduce all results of this paper and thus to become familiar with the package as quickly as possible.

Multimode multioffset phase analysis of surface waves, a new approach to extend MOPA to higher modes

2020 ◽  
Vol 221 (3) ◽  
pp. 1802-1819
Author(s):  
I Barone ◽  
C Strobbia ◽  
G Cassiani
Keyword(s):  
Wave Propagation ◽  
Surface Wave ◽  
Phase Analysis ◽  
Damping Ratio ◽  
Real Data ◽  
Wave Dispersion ◽  
Spatial Period ◽  
Lateral Velocity ◽  
Surface Wave Dispersion ◽  
Surface Wave Propagation

SUMMARY Multioffset phase analysis (MOPA) is a fairly recent technique for evaluating seismic surface wave dispersion and estimating the presence of lateral variations. The main limitation of MOPA is that it is based on the assumption of one predominant mode, usually the fundamental mode, in the wave propagation. However, MOPA can be extended (at least) to the two-mode case: this new technique will be called multimode MOPA (MMMOPA). The method employs both amplitude and phase spectral information. The analysis is performed for each frequency independently. The presence of two modes causes the amplitude to have an oscillating behaviour as a function of offset (beats): the spatial period of the oscillating amplitude is identified, amplitude maxima and minima are extracted, and the local wavenumber is computed via linear regression. The resulting multimodal dispersion curve is consequently derived. Model uncertainties can be estimated by propagating the experimental phase and amplitude error variances through the different steps of the analysis all the way to the final phase velocities. An algorithm running the process in an automatic way has been implemented and tested on both synthetic and real data, with success. This is the base for future developments that, in the MOPA framework, can take into account rapid lateral velocity variations within the same acquisition window and estimate the modal absorption, for the estimation of the damping ratio, even in the presence of multimode surface wave propagation.

Extracting surface wave dispersion curves from asynchronous seismic stations: method and application

2021 ◽  
Author(s):  
Hao Rao ◽  
Yinhe Luo ◽  
Kaifeng Zhao ◽  
Yingjie Yang
Keyword(s):  
Surface Wave ◽  
Phase Velocity ◽  
Ambient Noise ◽  
Wave Dispersion ◽  
Surface Wave Dispersion ◽  
Seismic Stations ◽  
Seismic Arrays ◽  
Single Station ◽  
Path Coverage ◽  
Noise Data

Summary Correlation of the coda of Empirical Green's functions from ambient noise can be used to reconstruct Empirical Green's function between two seismic stations deployed different periods of time. However, such method requires a number of source stations deployed in the area surrounding a pair of asynchronous stations, which limit its applicability in cases where there are not so many available source stations. Here, we propose an alternative method, called two-station C2 method, which uses one single station as a virtual source to retrieve surface wave phase velocities between a pair of asynchronous stations. Using ambient noise data from USArray as an example, we obtain the interstation C2 functions using our C2 method and the traditional cross-correlation functions (C1 functions). We compare the differences between the C1 and C2 functions in waveforms, dispersion measurements, and phase velocity maps. Our results show that our C2 method can obtain reliable interstation phase velocity measurements, which can be used in tomography to obtain reliable phase velocity maps. Our method can significantly improve ray path coverage from asynchronous seismic arrays and enhance the resolution in ambient noise tomography for areas between asynchronous seismic arrays.

scholarly journals Computation of surface wave dispersion for multilayered anisotropic media

1962 ◽  
Vol 52 (2) ◽  
pp. 321-332 ◽  
Author(s):  
David G. Harkrider ◽  
Don L. Anderson
Keyword(s):  
Surface Wave ◽  
Rayleigh Wave ◽  
Rayleigh Waves ◽  
Love Wave ◽  
Transversely Isotropic ◽  
Wave Dispersion ◽  
Surface Wave Dispersion ◽  
Independent Evidence ◽  
Anisotropic Layers ◽  
Love Wave Dispersion

ABSTRACT With the program described in this paper it is now possible to compute surface wave dispersion in a solid heterogeneous halfspace containing up to 200 anisotropic layers. Certain discrepancies in surface wave observations, such as disagreement between Love and Rayleigh wave data and other independent evidence, suggest that anisotropy may be important in some seismological problems. In order to study the effect of anisotropy on surface wave dispersion a program was written for an IBM 7090 computer which will compute dispersion curves and displacements for Rayleigh waves in a layered halfspace in which each layer is transversely isotropic. A simple redefinition of parameters makes it possible to use existing programs to compute Love wave dispersion.

Surface-wave dispersion spectrum inversion method applied to Love and Rayleigh waves recorded by distributed acoustic sensing

Geophysics ◽  
2021 ◽  
Vol 86 (1) ◽  
pp. EN1-EN12 ◽  
Author(s):  
Zhenghong Song ◽  
Xiangfang Zeng ◽  
Clifford H. Thurber
Keyword(s):  
Surface Wave ◽  
Wave Velocity ◽  
Love Wave ◽  
Wave Dispersion ◽  
Dynamic Strain ◽  
Inversion Method ◽  
Data Sets ◽  
Surface Wave Dispersion ◽  
Acoustic Sensing ◽  
Distributed Acoustic Sensing

Recently, distributed acoustic sensing (DAS) has been applied to shallow seismic structure imaging providing dense spatial sampling at a relatively low cost. DAS on a standard straight fiber-optic cable mostly records axial dynamic strain, which makes it difficult to separate the Rayleigh and Love wavefields. As a result, the mixed Rayleigh and Love wave signals cannot be used in the conventional surface-wave dispersion inversion method. Therefore, it is often ensured that the source and the cable are in the same line and only Rayleigh wave dispersion is used, which limits the constraints on structure and model resolution. We have inverted surface-wave dispersion spectra instead of dispersion curves. This inversion method can use mixed Rayleigh and Love waves recorded when the source and receiver array are not aligned. The multiple-channel records are transformed to the frequency domain, and a slant stack method is used to construct the dispersion spectra. The genetic algorithm method is used to obtain an optimal S-wave velocity model that minimizes the difference between theoretical and observed dispersion spectra. A series of synthetic tests are conducted to validate our method. The results suggest that our method not only improves the flexibility of the acquisition system design, but the Love wave data also provide additional constraints on the structure. Our method is applied to the active source and ambient noise data sets acquired at a geothermal site and provides consistent results for different data sets and acquisition geometries. The sensitivity of the dispersion spectra to layer thickness, density, and P-wave velocity is also discussed. With our method, the amount of usable data can be increased, helping deliver better subsurface images.

Crustal structure of the Mediterranean Sea Part II. Phase velocity and travel times

1969 ◽  
Vol 59 (1) ◽  
pp. 23-42
Author(s):  
Gonzalo Payo
Keyword(s):  
Surface Wave ◽  
Phase Velocity ◽  
Mediterranean Sea ◽  
Upper Mantle ◽  
Wave Dispersion ◽  
Mantle Structure ◽  
Low Velocity ◽  
Surface Wave Dispersion ◽  
The Mediterranean ◽  
Velocity Channel

Abstract A large number of observations of phase velocity of Love and Rayleigh waves have been used in order to determine the crust-mantle structure of the Mediterranean Sea. These velocities have been measured by using records from the Standard Stations located in the Mediterranean borders. The empirical dispersion curves have been compared with those of several models computed for this purpose. Travel-time curves of body waves for paths crossing the Mediterranean region, making use of all possible coastal stations and local earthquakes, have been found to substantiate the results from the surface wave dispersion. Also the value of the Bouguer anomaly in different points of the region was considered in the determination of the crustal thickness, as well as some measurements of group velocity from clear observations of higher modes. The crust-mantle structure under the Mediterranean Sea was found to be formed by two clearly distinct zones which correspond roughly to the areas to the west and east of Italy. The western zone, between Italy and Spain, is of oceanic type with a thin crust (about 14 km) and a low-velocity channel in the Upper Mantle. In the eastern zone, south of Greece, the crust (some 23 km thick) shows a great thickness of the uppermost sedimentary layers, which gives rise to very low velocities of short-period surface waves in that region. Love waves with group velocities smaller than those of Rayleigh have been clearly observed in a large number of earthquakes in this region. The surface wave dispersion as well as the travel-time curves of P and S waves of this zone indicate the existence of a low-velocity channel in the Upper Mantle.

Surface waves on multilayered anelastic media

1971 ◽  
Vol 61 (4) ◽  
pp. 893-912
Author(s):  
Fred Schwab ◽  
Leon Knopoff
Keyword(s):  
Phase Velocity ◽  
Love Wave ◽  
Layer Structure ◽  
Body Wave ◽  
Computation Time ◽  
Wave Dispersion ◽  
Low Velocity ◽  
Surface Wave Dispersion ◽  
Significant Figures ◽  
Love Wave Dispersion

abstract Surface-wave dispersion computations for perfectly-elastic media are generalized to allow dispersion-attenuation computations for anelastic media. In each layer, frequency-dependent, body-wave phase velocity and attenuation are taken into account directly. For a 50-layer structure, a single Love-wave dispersion-attenuation point can be determined in 0.28 sec—the phase velocity containing about 16 significant figures and the phase attenuation about 14, where 16 decimal digits are used in computations on an IBM 360/91 computer. Accuracies of 7 significant figures can be obtained in 0.13 sec. To this latter accuracy, the determination of the Love-wave dispersion and attentuation for an anelastic structure takes about 6.8 times the amount of computation time required to compute the dispersion for the comparable perfectly-elastic structure. The technique is applied to Love waves on an anelastic, radially heterogeneous sphere. A family of low-velocity zone channel waves is identified and investigated. A possible explanation for the disappearance of Lg across large oceanic paths is offered.

Improved Surface Wave Dispersion Models, Amplitude Measurements and Azimuth Estimates

2005 ◽  
Author(s):  
Jeffry L. Stevens ◽  
David A. Adams ◽  
G. E. Baker ◽  
Mariana G. Eneva ◽  
Heming Xu
Keyword(s):  
Surface Wave ◽  
Wave Dispersion ◽  
Dispersion Models ◽  
Surface Wave Dispersion
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