Practical technique for analysing free-field response of horizontally layered viscoelastic half-space excited by vertically travelling seismic waves

The interaction of lateral structural inertia forces with horizontal seismic motion is formulated in terms of an integral equation of the Volterra type. By means of normal mode theory the inertia force at the base of the structure is expressed as a function of the foundation motion. After the motion of the two-dimensional elastic half space resulting from a uniform horizontal foundation force varying arbitrarily with time over a specified interval on the boundary of the half space has been determined, the interaction equation is derived. Numerical studies for two free-field acceleration inputs are made for different ground stiffnesses and structural characteristics. The first of these free-field inputs is a ramp sine function and the second is the east-west ground acceleration recorded at Golden Gate Park during the 1957 San Francisco earthquake. The interaction effects for structures similar to nuclear power plants prove to be significant.

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Electroacoustics. Methods to determine corrections to obtain the free-field response of a sound level meter

10.3403/30194377u ◽

2015 ◽

Keyword(s):

Free Field ◽

Sound Level ◽

Sound Level Meter ◽

Field Response ◽

Level Meter

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Seismic Waves in a Laterally Inhomogeneous Layered Medium, Part I: Theory

Journal of Applied Mechanics ◽

10.1115/1.2787293 ◽

1997 ◽

Vol 64 (1) ◽

pp. 50-58 ◽

Cited By ~ 11

Author(s):

Ruichong Zhang ◽

Liyang Zhang ◽

Masanobu Shinozuka

Keyword(s):

Wave Field ◽

Half Space ◽

Seismic Waves ◽

Scattered Wave ◽

Inhomogeneous Layer ◽

Dislocation Source ◽

Seismic Dislocation ◽

Body Forces ◽

The Mean ◽

Layered Half Space

Seismic waves in a layered half-space with lateral inhomogeneities, generated by a buried seismic dislocation source, are investigated in these two consecutive papers. In the first paper, the problem is formulated and a corresponding approach to solve the problem is provided. Specifically, the elastic parameters in the laterally inhomogeneous layer, such as P and S wave speeds and density, are separated by the mean and the deviation parts. The mean part is constant while the deviation part, which is much smaller compared to the mean part, is a function of lateral coordinates. Using the first-order perturbation approach, it is shown that the total wave field may be obtained as a superposition of the mean wave field and the scattered wave field. The mean wave field is obtainable as a response solution for a perfectly layered half-space (without lateral inhomogeneities) subjected to a buried seismic dislocation source. The scattered wave field is obtained as a response solution for the same layered half-space as used in the mean wave field, but is subjected to the equivalent fictitious distributed body forces that mathematically replace the lateral inhomogeneities. These fictitious body forces have the same effects as the existence of lateral inhomogeneities and can be evaluated as a function of the inhomogeneity parameters and the mean wave fleld. The explicit expressions for the responses in both the mean and the scattered wave fields are derived with the aid of the integral transform approach and wave propagation analysis.

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Free-field response from inclined SH-waves and love-waves

Earthquake Engineering & Structural Dynamics ◽

10.1002/eqe.4290100607 ◽

1982 ◽

Vol 10 (6) ◽

pp. 823-845 ◽

Cited By ~ 21

Author(s):

John P. Wolf ◽

Pius Obernhuber

Keyword(s):

Free Field ◽

Love Waves ◽

Sh Waves ◽

Field Response

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Diffraction of elastic waves by a fluid-filled crack in a fluid-saturated poroelastic half-space

Geophysical Journal International ◽

10.1093/gji/ggab043 ◽

2021 ◽

Author(s):

Zhongxian Liu ◽

Jiaqiao Liu ◽

Sibo Meng ◽

Xiaojian Sun

Keyword(s):

Half Space ◽

Seismic Waves ◽

Incident Angle ◽

Excitation Frequency ◽

Vertical Displacement ◽

Crack Model ◽

P Waves ◽

Amplification Effect ◽

Resonance Frequencies ◽

Angle Crack

Summary An indirect boundary element method (IBEM) is developed to model the two-dimensional (2D) diffraction of seismic waves by a fluid-filled crack in a fluid-saturated poroelastic half-space, using Green's functions computed considering the distributed loads, flow, and fluid characteristics. The influence of the fluid-filled crack on the diffraction characteristics is investigated by analyzing key parameters, such as the excitation frequency, incident angle, crack width and depth, and medium porosity. The results for the fluid-filled crack model are compared to those for the fluid-free crack model under the same conditions. The numerical results demonstrate that the fluid-filled crack has a significant amplification effect on the surface displacements, and that the effect of the depth of the fluid-filled crack is more complex compared to the influence of other parameters. The resonance diffraction generates an amplification effect in the case of normally incident P waves. Furthermore, the horizontal and vertical displacement amplitudes reach 4.2 and 14.1, respectively. In the corresponding case of the fluid-free crack, the vertical displacement amplitude is only equal to 4.1, indicating the amplification effect of the fluid in the crack. Conversely, for normally incident SV waves at certain resonance frequencies, the displacement amplitudes above a fluid-filled crack may be lower than the displacement amplitudes observed in the corresponding case of a fluid-free crack.

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Seismic waves from a horizontal stress discontinuity in a layered solid

Bulletin of the Seismological Society of America ◽

10.1785/bssa0720051483 ◽

1982 ◽

Vol 72 (5) ◽

pp. 1483-1498

Author(s):

F. Abramovici ◽

E. R. Kanasewich ◽

P. G. Kelamis

Keyword(s):

Half Space ◽

Seismic Waves ◽

Horizontal Stress ◽

Radial Component ◽

Elastic Half Space ◽

Homogeneous Layer ◽

Approximate Methods ◽

Crustal Layer ◽

Finite Fault ◽

Stress Discontinuity

abstract The displacement components for a horizontal stress discontinuity along a buried finite fault in an elastic homogeneous layer on top of an elastic half-space are given analytically in terms of generalized rays. For a particular case of a concentrated horizontal force pointing in an arbitrary direction, detailed time-dependent expressions are given. For a simple model of a “crustal” layer over a “mantle” half-space, the numerical seismograms in the near- and intermediate-field show some interesting features. These include a prominent group of compressional waves whose radial component is substantial at distances four times the crustal thickness. All the dominant shear arrivals (s, SS, and sSS) are important and show large variations of amplitude as the source depth and receiver distance are varied. Some of the prominent individual generalized rays are shown, and it is found that they can be grouped naturally into families based on the number of interactions with the boundaries. The subdivision into individual generalized rays is useful for analysis and for checks on the numerical stability of the synthetic seismograms. Since the solution is analytic and the numerical evaluation is complete up to any desired time, the results are useful in comparing other approximate methods for the computation of seismograms.

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