Seismic signatures of permeability in heterogeneous porous media

Geophysics ◽  
1999 ◽  
Vol 64 (1) ◽  
pp. 99-103 ◽  
Author(s):  
Sergei A. Shapiro ◽  
Tobias M. Müller
Keyword(s):  
Porous Media ◽  
Seismic Waves ◽  
Heterogeneous Systems ◽  
Low Frequency ◽  
Heterogeneous Porous Media ◽  
Permeability Tensor ◽  
Hydraulic Permeability ◽  
Frequency Range ◽  
P Waves

In homogeneous poroelastic systems, the permeability tensor practically does not influence propagating seismic waves in the low frequency range (0–1000 Hz; see, e.g., Schmitt, 1989; Gelinsky and Shapiro, 1996). In this paper, we show that this situation changes in heterogeneous systems such as, layered or fractured sediments. Due to the heterogeneities of poroelastic structures, the attenuation of P-waves is influenced by the permeability in an enhanced way. We show, however, that such a “seismic permeability” can differ very strongly from the hydraulic permeability.

A periodic seismic isolation foundation with an extremely broad low-frequency attenuation zone: Theoretical analysis and experimental verification

2021 ◽  
pp. 136943322110646
Author(s):  
Peng Zhou ◽  
Shui Wan ◽  
Xiao Wang ◽  
Yingbo Zhu ◽  
Muyun Huang
Keyword(s):  
Seismic Isolation ◽  
Seismic Waves ◽  
Periodic Structures ◽  
Finite Size ◽  
Low Frequency ◽  
Bridge Structure ◽  
Engineering Structures ◽  
P Waves ◽  
New Type ◽  
Dominant Frequencies

The attenuation zones (AZs) of periodic structures can be used for seismic isolation design. To cover the dominant frequencies of more seismic waves, this paper proposes a new type of periodic isolation foundation (PIF) with an extremely wide low-frequency AZ of 3.31 Hz–17.01 Hz composed of optimized unit A with a wide AZ and optimized unit B with a low-frequency AZ. The two kinds of optimized units are obtained by topology optimization on the smallest periodic unit with the coupled finite element-genetic algorithm (GA) methodology. The transmission spectra of shear waves and P-waves through the proposed PIF of finite size are calculated, and the results show that the AZ of the PIF is approximately the superposition of the AZs of the two kinds of optimized units. Additionally, shake tests on a scale PIF specimen are performed to verify the attenuation performance for elastic waves within the designed AZs. Furthermore, numerical simulations show that the acceleration responses of the bridge structure with the proposed PIF are attenuated significantly compared to those with a concrete foundation under the action of different seismic waves. Therefore, the newly proposed PIF is a promising option for the reduction of seismic effects in engineering structures.

scholarly journals MEASUREMENT OF PREFERENTIAL FLOW DURING INFILTRATION AND EVAPORATION IN POROUS MEDIA

2017 ◽  
Vol 43 (4) ◽  
pp. 1831
Author(s):  
A. Papafotiou ◽  
C. Schütz ◽  
P. Lehmann ◽  
P. Vontobel ◽  
D. Or ◽  
...  
Keyword(s):  
Porous Media ◽  
Water Distribution ◽  
Preferential Flow ◽  
Unsaturated Flow ◽  
Coupling Effect ◽  
Heterogeneous Systems ◽  
Heterogeneous Porous Media ◽  
Richards Equation ◽  
Hydraulic Coupling ◽  
Experimental Findings

Infiltration and evaporation are governing processes for water exchange between soil and atmosphere. In addition to atmospheric supply or demand, infiltration and evaporation rates are controlled by the material properties of the subsurface and the interplay between capillary, viscous and gravitational forces. This is commonly modeled with semi-empirical approaches using continuum models, such as the Richards equation for unsaturated flow. However, preferential flow phenomena often occur, limiting or even entirely suspending the applicability of continuum-based models. During infiltration, unstable fingers may form in homogeneous or heterogeneous porous media. On the other hand, the evaporation process may be driven by the hydraulic coupling of materials with different hydraulic functions found in heterogeneous systems. To analyze such preferential flow processes, water distribution was monitored in infiltration and evaporation lab experiments using neutron transmission techniques. Measurements were performed in 2D and 3D, using homogeneous and heterogeneous setups. The experimental findings demonstrate the fingering effect in infiltration and how it is influenced by the presence of fine inclusions in coarse background material. During evaporation processes, the hydraulic coupling effect is found to control the evaporation rate, limiting the modeling of water balances between soil and surface based on surface information alone.

scholarly journals Modeling P waves in seismic noise correlations: Application to fault monitoring using train traffic sources

2021 ◽  
Author(s):  
Korbinian Sager ◽  
Victor Tsai ◽  
Yixiao Sheng ◽  
Florent Brenguier ◽  
Pierre Boué ◽  
...  
Keyword(s):  
Green’S Function ◽  
Surface Waves ◽  
Green's Function ◽  
Seismic Waves ◽  
Low Frequency ◽  
Body Waves ◽  
Noise Sources ◽  
P Waves ◽  
Promising Alternative ◽  
Fault Monitoring

The theory of Green's function retrieval essentially requires homogeneously distributed noise sources. Even though these conditions are not fulfilled in nature, low-frequency (<1 Hz) surface waves generated by ocean-crust interactions have been used successfully to image the crust with unprecedented spatial resolution. In contrast to low-frequency surface waves, high-frequency (>1 Hz) body waves have a sharper, more localized sensitivity to velocity contrasts and temporal changes at depth. In general, their retrieval using seismic interferometry is challenging, and recent studies focus on powerful, localized noise sources. They have proven to be a promising alternative but break the assumptions of Green's function retrieval. In this study, we present an approach to model correlations between P waves for these scenarios and analyze their sensitivity to 3D Earth structure. We perform a series of numerical experiments to advance our understanding of these signals and prepare for an application to fault monitoring. In the considered cases, the character of the signals strongly diverges from Green's function retrieval, and the sensitivity to structure has significant contributions in the source direction. An accurate description of the underlying physics allows us to reproduce observations made in the context of monitoring the San Jacinto Fault in California using train-generated seismic waves. This approach provides new perspectives for detecting and localizing temporal velocity changes previously unnoticed by commonly exploited surface-wave reconstructions.

Poroelastic analysis of permeability effects in thinly layered porous media

Geophysics ◽  
2009 ◽  
Vol 74 (6) ◽  
pp. N49-N54 ◽  
Author(s):  
Haitao Ren ◽  
Gennady Goloshubin ◽  
Fred J. Hilterman
Keyword(s):  
Porous Media ◽  
Seismic Data ◽  
Seismic Waves ◽  
Heterogeneous Porous Media ◽  
High Impedance ◽  
Numerical Studies ◽  
Layered Porous Media ◽  
Significant Attenuation ◽  
Nondispersive Medium ◽  
Wave Induced

The mechanism of wave-induced fluid flow, which causes significant attenuation and dispersion of seismic waves in heterogeneous porous media, opens a potential opportunity to estimate fluid-mobility properties from seismic data. However, the permeability effects on seismic data vary for different reservoir environments, so rules of thumb are difficult to establish. Two types of reservoir models were selected. One represents shallow, unconsolidated, low-impedance reservoirs. The other represents deep, consolidated, high-impedance reservoirs. Using analytic equations and wave-propagation numerical studies, permeability effects were investigated on the magnitude and phase of normal-incident reflection coefficients from an interface between an upper nondispersive medium and a lower thinly layered porous medium. The study found that permeability can affect reflection amplitudes significantly. For high-impedance reservoirs, magnitude of the reflection coefficient decreases when permeability increases. However, for low-impedance reservoirs, reflection magnitude increases as permeability increases.

Seismic waves from the underground atomic explosion in Nevada

1959 ◽  
Vol 49 (1) ◽  
pp. 11-32
Author(s):  
B. F. Grossling
Keyword(s):  
Time Scale ◽  
Seismic Waves ◽  
Vertical Component ◽  
Short Wave ◽  
Apparent Velocity ◽  
Frequency Range ◽  
P Waves ◽  
Frequency Spectra ◽  
Arrival Times ◽  
Absolute Amplitude

&gt;Abstract Seismic waves from the underground atomic explosion of September 19, 1957, were recorded for 45 minutes on multichannel magnetic tape at a point 25 miles north of Holbrook, Arizona, about 370 miles from their source. Twelve vertical-component seismometers were laid out in the form of an L 5,280 ft. by 1,600 ft. to permit determinations of apparent velocity and of direction of arrival. The frequency range recorded, about 6 to 40 cps, was higher than usual in earthquake seismology. During tape playback, supplementary filtering, gain adjustments, and changes in time scale served to improve the quality and legibility of the records. The playback seismograms reveal strikingly well not only to Pn and P* waves transmitted and refracted by the crust, but also many others as well. Some of these, as clearly indicated by their directions of arrival, did not originate from the explosion. We have attempted only an elementary interpretation, our main purpose being to make the data available to anyone who might be interested in them. The relatively short wave lengths of the recorded events may make them of unusual significance. In addition to arrival times, we made a few measurements of absolute amplitude and of frequency spectra.

SEISMIC WAVE PROPAGATION

Geophysics ◽  
1950 ◽  
Vol 15 (1) ◽  
pp. 50-60 ◽  
Author(s):  
D. H. Clewell ◽  
R. F. Simon
Keyword(s):  
High Frequency ◽  
Seismic Waves ◽  
Low Frequency ◽  
Seismic Energy ◽  
Seismic Wave Propagation ◽  
Frequency Range ◽  
Energy Propagation ◽  
Scattered Energy ◽  
Solid Friction ◽  
Theoretical Considerations

Speculations are made regarding the significance of the well‐known observation that seismic reflection energy is usually in the frequency range of from 20 to 100 cycles per second. The general absence of reflected energy below 20 cps is attributed to the fact that the wavelengths of seismic waves in this frequency range are becoming large compared to the thicknesses of reflecting beds; accordingly, the reflection coefficients are low with the results that the geologic section appears more or less homogeneous, the low frequency energy is unweakened by reflections, is transmitted efficiently, and can only return to the surface by refraction. As the frequency is increased the wavelengths become comparable to the vertical discontinuities represented by stratification and more efficient reflection takes place with the result that reflected energy is returned and detected at the surface. At still higher frequencies the wavelengths become comparable to small inhomogeneities distributed at random throughout the geologic section and the energy is therefore diffused and scattered to such an extent that transmission into the earth is limited. This weakening of the main wave front by scattering, plus the weakening by absorption processes involving viscous and solid friction, constitute an effective cutting off of high frequency transmission. The high frequency scattered energy diffuses back to the surface and appears on the seismogram as “hash,” unless eliminated by filters, or is absorbed before it reaches the surface. Such a speculative picture of seismic energy propagation accounts qualitatively for (1) the continuous reception of random energy that is always superimposed upon the reflection energy, (2) the tendency for deep reflections to be of lower frequency than shallow reflections, and (3) the fact that theoretical considerations of absorption do not always account for known attenuation of high frequency seismic energy.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

Dynamic Damping and Stiffness Characteristics of the Rolling Tire

2001 ◽  
Vol 29 (4) ◽  
pp. 258-268 ◽  
Author(s):  
G. Jianmin ◽  
R. Gall ◽  
W. Zuomin
Keyword(s):  
Dynamic Behavior ◽  
Variable Parameter ◽  
Low Frequency ◽  
Vertical Load ◽  
Frequency Range ◽  
Inflation Pressure ◽  
Vehicle Simulation ◽  
Dynamic Damping ◽  
Speed Range ◽  
Stiffness Characteristics

Abstract A variable parameter model to study dynamic tire responses is presented. A modified device to measure terrain roughness is used to measure dynamic damping and stiffness characteristics of rolling tires. The device was used to examine the dynamic behavior of a tire in the speed range from 0 to 10 km/h. The inflation pressure during the tests was adjusted to 160, 240, and 320 kPa. The vertical load was 5.2 kN. The results indicate that the damping and stiffness decrease with velocity. Regression formulas for the non-linear experimental damping and stiffness are obtained. These results can be used as input parameters for vehicle simulation to evaluate the vehicle's driving and comfort performance in the medium-low frequency range (0–100 Hz). This way it can be important for tire design and the forecasting of the dynamic behavior of tires.

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