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Beatriz Quintal - One of the best experts on this subject based on the ideXlab platform.
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measurements of Seismic Attenuation and transient fluid pressure in partially saturated berea sandstone evidence of fluid flow on the mesoscopic scale
Geophysical Journal International, 2013Co-Authors: Nicola Tisato, Beatriz QuintalAbstract:S U M M A R Y A novel laboratory technique is proposed to investigate wave-induced fluid flow on the mesoscopic scale as a mechanism for Seismic Attenuation in partially saturated rocks. This technique combines measurements of Seismic Attenuation in the frequency range from 1 to 100 Hz with measurements of transient fluid pressure as a response of a step stress applied on top of the sample. We used a Berea sandstone sample partially saturated with water. The laboratory results suggest that wave-induced fluid flow on the mesoscopic scale is dominant in partially saturated samples. A 3-D numerical model representing the sample was used to verify the experimental results. Biot’s equations of consolidation were solved with the finite-element method. Wave-induced fluid flow on the mesoscopic scale was the only Attenuation mechanism accounted for in the numerical solution. The numerically calculated transient fluid pressure reproduced the laboratory data. Moreover, the numerically calculated Attenuation, superposed to the frequency-independent matrix anelasticity, reproduced the Attenuation measured in the laboratory in the partially saturated sample. This experimental—numerical fit demonstrates that wave-induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for Seismic Attenuation in partially saturated Berea sandstone.
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Modeling Seismic Attenuation due to wave-induced fluid flow in the mesoscopic scale to interpret laboratory measurements
Poromechanics V, 2013Co-Authors: Beatriz Quintal, Nicola TisatoAbstract:We measured Seismic Attenuation in the frequency range from 1 to 100 Hz and transient fluid pressure in partially saturated Berea sandstone. The sample was saturated with 97% water (3% air). To test whether fluid flow in the mesoscopic scale was the main cause of the measured Attenuation, we performed numerical modeling to compute Attenuation and transient fluid pressure on a 3D poroelastic model that represents the partially saturated sample. Waveinduced fluid flow in the mesoscopic scale was the only Attenuation mechanism accounted for in the numerical solution. The numerical results reproduced the laboratory data for transient fluid pressure. The numerically calculated Attenuation, superposed to the frequency-independent Attenuation measured in the dry rock, reproduced Attenuation measured in the partially saturated sample. These results show that wave-induced fluid flow in the mesoscopic scale is the dominant mechanism for the frequencydependent component of Seismic Attenuation in partially saturated sandstone.
Nicola Tisato - One of the best experts on this subject based on the ideXlab platform.
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measurements of Seismic Attenuation and transient fluid pressure in partially saturated berea sandstone evidence of fluid flow on the mesoscopic scale
Geophysical Journal International, 2013Co-Authors: Nicola Tisato, Beatriz QuintalAbstract:S U M M A R Y A novel laboratory technique is proposed to investigate wave-induced fluid flow on the mesoscopic scale as a mechanism for Seismic Attenuation in partially saturated rocks. This technique combines measurements of Seismic Attenuation in the frequency range from 1 to 100 Hz with measurements of transient fluid pressure as a response of a step stress applied on top of the sample. We used a Berea sandstone sample partially saturated with water. The laboratory results suggest that wave-induced fluid flow on the mesoscopic scale is dominant in partially saturated samples. A 3-D numerical model representing the sample was used to verify the experimental results. Biot’s equations of consolidation were solved with the finite-element method. Wave-induced fluid flow on the mesoscopic scale was the only Attenuation mechanism accounted for in the numerical solution. The numerically calculated transient fluid pressure reproduced the laboratory data. Moreover, the numerically calculated Attenuation, superposed to the frequency-independent matrix anelasticity, reproduced the Attenuation measured in the laboratory in the partially saturated sample. This experimental—numerical fit demonstrates that wave-induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for Seismic Attenuation in partially saturated Berea sandstone.
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Modeling Seismic Attenuation due to wave-induced fluid flow in the mesoscopic scale to interpret laboratory measurements
Poromechanics V, 2013Co-Authors: Beatriz Quintal, Nicola TisatoAbstract:We measured Seismic Attenuation in the frequency range from 1 to 100 Hz and transient fluid pressure in partially saturated Berea sandstone. The sample was saturated with 97% water (3% air). To test whether fluid flow in the mesoscopic scale was the main cause of the measured Attenuation, we performed numerical modeling to compute Attenuation and transient fluid pressure on a 3D poroelastic model that represents the partially saturated sample. Waveinduced fluid flow in the mesoscopic scale was the only Attenuation mechanism accounted for in the numerical solution. The numerical results reproduced the laboratory data for transient fluid pressure. The numerically calculated Attenuation, superposed to the frequency-independent Attenuation measured in the dry rock, reproduced Attenuation measured in the partially saturated sample. These results show that wave-induced fluid flow in the mesoscopic scale is the dominant mechanism for the frequencydependent component of Seismic Attenuation in partially saturated sandstone.
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A new laboratory system for the measurement of low frequency Seismic Attenuation
SEG Technical Program Expanded Abstracts, 2010Co-Authors: Claudio Madonna, Nicola Tisato, Sebastien Boutareaud, David MainpriceAbstract:The study of wave Attenuation in partially saturated porous rocks over a broad frequency range provides valuable information about the fluid system of reservoirs, which are inherently multiple phase fluid system. Until now, not much laboratory data have been collected in the Seismically relevant low frequency range and existing literature data on partially saturated rock are very limited. The main goal of our work is to experimentally measure the bulk Seismic Attenuation on fluid-bearing rocks, using natural rock samples in an efficient way at in situ conditions. We are currently fine-tuning our Attenuation measurement prototype. Preliminary bench-top results are promising and show consistency with reported experimental data with dry, partially and fully fluid saturated rocks. Measurements with the machine are accurate and precise.
Klaus Holliger - One of the best experts on this subject based on the ideXlab platform.
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Modeling Forced Imbibition Processes and the Associated Seismic Attenuation in Heterogeneous Porous Rocks
Journal of Geophysical Research: Solid Earth, 2017Co-Authors: Santiago G. Solazzi, J. Germán Rubino, Tobias M Muller, Luis Guarracino, Klaus HolligerAbstract:Quantifying Seismic Attenuation during laboratory imbibition experiments can provide useful information towards the use of Seismic waves for monitoring injection and extraction of fluids in the Earth's crust. However, a deeper understanding of the physical causes producing the observed Attenuation is needed for this purpose. In this work, we analyze Seismic Attenuation due to mesoscopic wave-induced fluid flow (WIFF) produced by realistic fluid distributions representative of imbibition experiments. To do so, we first perform two-phase flow simulations in a heterogeneous rock sample to emulate a forced imbibition experiment. We then select a sub-sample of the considered rock containing the resulting time-dependent saturation fields, and apply a numerical upscaling procedure to compute the associated Seismic Attenuation. By exploring both saturation distributions and Seismic Attenuation we observe that two manifestations of WIFF arise during imbibition experiments: the first one is produced by the compressibility contrast associated with the saturation front, whereas the second one is due to the presence of patches containing very high amounts of water that are located behind the saturation front. We demonstrate that while the former process is expected to play a significant role in the case of high injection rates, which are associated with viscous-dominated imbibition processes, the latter becomes predominant during capillary-dominated processes, that is, for relatively low injection rates. We conclude that this kind of joint numerical analysis constitutes a useful tool for improving our understanding of the physical mechanisms producing Seismic Attenuation during laboratory imbibition experiments.
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Seismic Attenuation and velocity dispersion in fractured rocks: The role played by fracture contact areas
Geophysical Prospecting, 2014Co-Authors: J. Germán Rubino, Marco Milani, Tobias M Muller, Klaus HolligerAbstract:The presence of fractures in fluid-saturated porous rocks is usually associated with strong Seismic P-wave Attenuation and velocity dispersion. This energy dissipation can be caused by oscillatory wave-induced fluid pressure diffusion between the fractures and the host rock, an intrinsic Attenuation mechanism generally referred to as wave-induced fluid flow. Geological observations suggest that fracture surfaces are highly irregular at the millimetre and sub-millimetre scale, which finds its expression in geometrical and mechanical complexities of the contact area between the fracture faces. It is well known that contact areas strongly affect the overall mechanical fracture properties. However, existing models for Seismic Attenuation and velocity dispersion in fractured rocks neglect this complexity. In this work, we explore the effects of fracture contact areas on Seismic P-wave Attenuation and velocity dispersion using oscillatory relaxation simulations based on quasi-static poroelastic equations. We verify that the geometrical and mechanical details of fracture contact areas have a strong impact on Seismic signatures. In addition, our numerical approach allows us to quantify the vertical solid displacement jump across fractures, the key quantity in the linear slip theory. We find that the displacement jump is strongly affected by the geometrical details of the fracture contact area and, due to the oscillatory fluid pressure diffusion process, is complex-valued and frequency-dependent. By using laboratory measurements of stress-induced changes in the fracture contact area, we relate Seismic Attenuation and dispersion to the effective stress. The corresponding results do indeed indicate that Seismic Attenuation and phase velocity may constitute useful attributes to constrain the effective stress. Alternatively, knowledge of the effective stress may help to identify the regions in which wave induced fluid flow is expected to be the dominant Attenuation mechanism.
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Fracture Connectivity Effects on Seismic Attenuation
Poromechanics V, 2013Co-Authors: J. Germán Rubino, Tobias M Muller, Luis Guarracino, Klaus HolligerAbstract:An important characteristic of fractured rocks is their very high Seismic Attenuation, which so far has been assumed to be mainly produced by wave-induced fluid flow between the fractures and the embedding matrix. As this fluid pressure equilibration process is strongly controlled by the hydraulic properties of the heterogeneous rock sample, the resulting Seismic Attenuation must also be expected to contain information about fracture connectivity. To date, however, the importance of fracture connectivity with regard to the observed Seismic Attenuation is largely unknown. Using numerical oscillatory compressibility simulations based on Biot's quasi-static poroelastic equations we show that an important, and as of yet non-documented manifestation of wave-induced fluid flow arises in the presence of fracture connectivity. We demonstrate that this additional energy loss is mainly due to fluid flow within the fractures and operates only in the presence of connected fractures. We also show that this phenomenon is sensitive to the lengths, permeabilities, and intersection angles of the fractures. Correspondingly, it contains key information on the governing hydraulic properties of fractured rocks and hence should be accounted for whenever realistic Seismic models of such media are needed.
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Numerical analysis of anisotropic Seismic Attenuation and velocity dispersion in fractured media.
2013Co-Authors: Marco Milani, J. Germán Rubino, Tobias M Muller, Klaus HolligerAbstract:Fractures are present in most geological formations and they tend to dominate not only their mechanical but also, and in particular, their hydraulic properties. For these reasons, the detection and characterization of fractures constitutes a subject of great interest in several fields of Earth sciences, such as groundwater and contaminant hydrology, CO2 sequestration as well as geothermal and fossil energy exploration and production, among many others. Seismic Attenuation has been recognized as a key attribute for this purpose, as both laboratory and field experiments indicate that the presence of fractures usually produces very significant Attenuation and that this attribute tends to systematically increase with increasing fracture density. In the absence of fracture connectivity, this energy loss is generally considered to be primarily due to fluid flow between the fractures and the embedding porous matrix. That is, due to the very significant compressibility contrast between fractures and the embedding porous matrix, the propagation of Seismic waves can generate a strong fluid pressure gradient and associated fluid flow between the two domains, which in turn generates energy dissipation. Due to the typical geometrical characteristics of fractures, the associated Attenuation and velocity dispersion must be expected to be strongly anisotropic. In this work, we seek to explore the main characteristics of anisotropic Seismic Attenuation and velocity dispersion due to fluid flow between mesoscopic fractures and the embedding matrix. To this end, we apply numerical oscillatory compressibility and shear tests based on the quasi-static poro-elastic equations on two-dimensional synthetic rock samples containing representative mesoscopic fractures. Assuming that the considered rock sample can be effectively represented by a homogeneous transversely isotropic viscoelastic medium, such tests allow us to compute the corresponding complex-valued and frequency-dependent elements of the stiffness matrix. Finally, we perform an exhaustive sensitivity analysis to determine the role played by different properties of fractured porous rocks with regards to this energy dissipation mechanism as a function of the direction of Seismic wave propagation.
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Research note: Seismic Attenuation due to wave-induced fluid flow at microscopic and mesoscopic scales
Geophysical Prospecting, 2013Co-Authors: J. Germán Rubino, Klaus HolligerAbstract:ABSTRACT Wave‐induced fluid flow at microscopic and mesoscopic scales arguably constitutes the major cause of intrinsic Seismic Attenuation throughout the exploration Seismic and sonic frequency ranges. The quantitative analysis of these phenomena is, however, complicated by the fact that the governing physical processes may be dependent. The reason for this is that the presence of microscopic heterogeneities, such as micro‐cracks or broken grain contacts, causes the stiffness of the so‐called modified dry frame to be complex‐valued and frequency‐dependent, which in turn may affect the viscoelastic behaviour in response to fluid flow at mesoscopic scales. In this work, we propose a simple but effective procedure to estimate the Seismic Attenuation and velocity dispersion behaviour associated with wave‐induced fluid flow due to both microscopic and mesoscopic heterogeneities and discuss the results obtained for a range of pertinent scenarios.
Akiteru Takamori - One of the best experts on this subject based on the ideXlab platform.
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Control system for the Seismic Attenuation system(SAS) in TAMA300
Journal of Physics: Conference Series, 2008Co-Authors: K. Agatsuma, Ryutaro Takahashi, Koji Arai, Daisuke Tatsumi, M. Fukushima, T. Yamazaki, M. K. Fujimoto, Y. Arase, N. Nakagawa, Akiteru TakamoriAbstract:A new Seismic isolation system, TAMA Seismic Attenuation System (TAMA-SAS), was installed to TAMA300 in order to improve the sensitivity at low frequencies. Inertial damping is one of the hierarchical control systems of the TAMA-SAS which are employed to give full play to its ability. We have established two servo loops to control the Inverted Pendulum (IP) which composes the SAS. One is the servo loop using LVDT position sensors to keep the position of the IP. The other is the inertial damping which uses accelerometers to control the inertial motion of the IP for the horizontal direction. The fluctuation of the IP was reduced using our servo system. In addition, reduction of angular and longitudinal fluctuation of the mirror was also confirmed. These results indicate that the control for the IP properly works and the isolation performance of the TAMA-SAS was improved.
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Operational status of TAMA300 with the Seismic Attenuation system (SAS)
Classical and Quantum Gravity, 2008Co-Authors: Ryutaro Takahashi, Koji Arai, Daisuke Tatsumi, M. Fukushima, T. Yamazaki, M. K. Fujimoto, K. Agatsuma, Y. Arase, N. Nakagawa, Akiteru TakamoriAbstract:TAMA300 has been upgraded to improve the sensitivity at low frequencies after the last observation run in 2004. To avoid the noise caused by Seismic activities, we installed a new Seismic isolation system —- the TAMA Seismic Attenuation system (SAS). Four SAS towers for the test-mass mirrors were sequentially installed from 2005 to 2006. The recycled Fabry–Perot Michelson interferometer was successfully locked with the SAS. We confirmed the reduction of both length and angular fluctuations at frequencies higher than 1 Hz owing to the SAS.
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Design and prototype tests of a Seismic Attenuation system for the advanced-LIGO output mode cleaner
Classical and Quantum Gravity, 2006Co-Authors: Alessandro Bertolini, Riccardo Desalvo, C Galli, G Gennaro, M. Mantovani, S. Márka, Virginio Sannibale, Akiteru Takamori, C. I. TorrieAbstract:Both present LIGO and advanced LIGO (Ad-LIGO) will need an output mode cleaner (OMC) to reach the desired sensitivity. We designed a suitable OMC Seismically attenuated optical table fitting to the existing vacuum chambers (horizontal access module, HAM chambers). The most straightforward and cost-effective solution satisfying the Ad-LIGO Seismic Attenuation specifications was to implement a single passive Seismic Attenuation stage, derived from the 'Seismic Attenuation system' (SAS) concept. We built and tested prototypes of all critical components. On the basis of these tests and past experience, we expect that the passive Attenuation performance of this new design, called HAM-SAS, will match all requirements for the LIGO OMC, and all Ad-LIGO optical tables. Its performance can be improved, if necessary, by implementation of a simple active Attenuation loop at marginal additional cost. The design can be easily modified to equip the LIGO basic symmetric chamber (BSC) chambers and leaves space for extensive performance upgrades for future evolutions of Ad-LIGO. Design parameters and prototype test results are presented.
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Anatomy of the TAMA SAS Seismic Attenuation system
Classical and Quantum Gravity, 2002Co-Authors: Szabolcs Marka, Alessandro Bertolini, Riccardo Desalvo, Akiteru Takamori, Yukiyoshi Iida, Masaki Ando, Giancarlo Cella, Mitsuhiro Fukushima, Florian Jacquier, Seiji KawamuraAbstract:The TAMA SAS Seismic Attenuation system was developed to provide the extremely high level of Seismic isolation required by the next generation of interferometric gravitational wave detectors to achieve the desired sensitivity at low frequencies. Our aim was to provide good performance at frequencies above ~10 Hz, while utilizing only passive subsystems in the sensitive frequency band of the TAMA interferometric gravitational wave detectors. The only active feedback is relegated below 6 Hz and it is used to damp the rigid body resonances of the Attenuation chain. Simulations, based on subsystem performance characterizations, indicate that the system can achieve rms mirror residual motion measured in a few tens of nanometres. We will give a brief overview of the subsystems and point out some of the characterization results, supporting our claims of achieved performance. SAS is a passive, UHV compatible and low cost system. It is likely that extremely sensitive experiments in other fields will also profit from our study.
Takeshi Kimura - One of the best experts on this subject based on the ideXlab platform.
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Detailed Seismic Attenuation structure beneath Hokkaido, northeastern Japan: Arc‐arc collision process, arc magmatism, and seismotectonics
Journal of Geophysical Research: Solid Earth, 2014Co-Authors: Saeko Kita, Junichi Nakajima, Akira Hasegawa, Tomomi Okada, Kei Katsumata, Youichi Asano, Takeshi KimuraAbstract:In this study, we imaged a detailed Seismic Attenuation structure (frequency-independent Q−1) beneath Hokkaido, Japan, by merging waveform data from a dense permanent Seismic network with those from a very dense temporary network. Corner frequency of each event used for t* estimation was determined by the S coda wave spectral ratio method. The Seismic Attenuation (Qp−1) structure is clearly imaged at depths down to about 120 km. For the fore-arc side of Hokkaido, high-Qp zones are imaged at depths of 10 to 80 km in the crust and mantle wedge above the Pacific slab. Low-Qp zones are clearly imaged in the mantle wedge beneath the back-arc areas of eastern and southern Hokkaido. These low-Qp zones, extending from deeper regions, extend to the Moho beneath volcanoes, the locations of which are consistent with those of Seismic low-velocity regions. These results suggest that the mantle wedge upwelling flow occurs beneath Hokkaido, except in the area where there is a gap in the volcano chain. In contrast, an inhomogeneous Seismic Attenuation structure is clearly imaged beneath the Hokkaido corner. A broad low-Qp zone is located at depths of 0–60 km to the west of the Hidaka main thrust. The location almost corresponds to that of the Seismic low-velocity zone in the collision zone. The fault planes of the 1970 M6.7 and 1982 M7.1 earthquakes are located at the edges of this broad low-Qp zone. Observations in this study indicate that our findings contribute to understanding the detailed arc-arc collision process, magmatism, and seismotectonics beneath Hokkaido.
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detailed Seismic Attenuation structure beneath hokkaido northeastern japan arc arc collision process arc magmatism and seismotectonics
Journal of Geophysical Research, 2014Co-Authors: Saeko Kita, Junichi Nakajima, Akira Hasegawa, Tomomi Okada, Kei Katsumata, Youichi Asano, Takeshi KimuraAbstract:In this study, we imaged a detailed Seismic Attenuation structure (frequency-independent Q−1) beneath Hokkaido, Japan, by merging waveform data from a dense permanent Seismic network with those from a very dense temporary network. Corner frequency of each event used for t* estimation was determined by the S coda wave spectral ratio method. The Seismic Attenuation (Qp−1) structure is clearly imaged at depths down to about 120 km. For the fore-arc side of Hokkaido, high-Qp zones are imaged at depths of 10 to 80 km in the crust and mantle wedge above the Pacific slab. Low-Qp zones are clearly imaged in the mantle wedge beneath the back-arc areas of eastern and southern Hokkaido. These low-Qp zones, extending from deeper regions, extend to the Moho beneath volcanoes, the locations of which are consistent with those of Seismic low-velocity regions. These results suggest that the mantle wedge upwelling flow occurs beneath Hokkaido, except in the area where there is a gap in the volcano chain. In contrast, an inhomogeneous Seismic Attenuation structure is clearly imaged beneath the Hokkaido corner. A broad low-Qp zone is located at depths of 0–60 km to the west of the Hidaka main thrust. The location almost corresponds to that of the Seismic low-velocity zone in the collision zone. The fault planes of the 1970 M6.7 and 1982 M7.1 earthquakes are located at the edges of this broad low-Qp zone. Observations in this study indicate that our findings contribute to understanding the detailed arc-arc collision process, magmatism, and seismotectonics beneath Hokkaido.
