Deep cavity detection using propagation of seismic waves in homogenous half-space and layered soil media

2020 ◽  
Vol 21 (8) ◽  
pp. 1431-1441
Author(s):  
Sohrab Mirassi ◽  
Hossein Rahnema
Keyword(s):  
Half Space ◽  
Seismic Waves ◽  
Layered Soil ◽  
Cavity Detection ◽  
Deep Cavity ◽  
Soil Media

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

1997 ◽  
Vol 64 (1) ◽  
pp. 50-58 ◽  
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.

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

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.

Seismic waves from a horizontal stress discontinuity in a layered solid

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.

Dynamics of piles and pile groups in layered soil media

1991 ◽  
Vol 10 (8) ◽  
pp. 386-401 ◽  
Author(s):  
Amir M. Kaynia ◽  
Eduardo Kausel
Keyword(s):  
Layered Soil ◽  
Pile Groups ◽  
Soil Media

scholarly journals То the synchronous work of pulsed sources of seismic waves

2019 ◽  
pp. 75-79
Author(s):  
S. P. Ekomasov
Keyword(s):  
Control System ◽  
Response Time ◽  
Half Space ◽  
Seismic Waves ◽  
Time Interval ◽  
Shock Interaction ◽  
Seismic Efficiency ◽  
Pulse Type ◽  
The Stability ◽  
The Moment

Researches have been made with the use of a hydropneumatic source of seismic waves. This source on the realized efforts of the shock interaction with a soil half-space considerably exceeds all known designs of radiators (sources) of pulse type. In this regard it shows higher seismic efficiency. The most important characteristic of the work of the pulse sources of seismic waves is a stability of the response time — a time interval from the moment of giving of a signal for producing of the blow until the very blow. Only with the achievement of the necessary stability the work in the mode of grouping of sources and accumulation of signals is possible. Features of the formation of response time of a hydropneumatic source are given. The analysis of the assessment of the parameters of synchronism of the pulse sources is made by a modem control system of their work. An influence of the rigidity of the soil on the assessment of stability of the response time and synchronism is shown. The system of the assessment of the stability used in the existing pulse sources at its application does not reflect the actual stability of response time in the radiators possessing a big force of blow.

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