Sensitivity of permeability changes to different earthquakes in a fault zone: Possible evidence of dependence on the frequency of seismic waves

2021 ◽  
Author(s):  
Xin Liao ◽  
Yun Shi ◽  
Chun‐Ping Liu ◽  
Guangcai Wang
Keyword(s):  
Fault Zone ◽  
Seismic Waves ◽  
Permeability Changes

scholarly journals Numerical Analysis of the Seismic Response of Tunnel Composite Lining Structures across an Active Fault

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zude Ding ◽  
Mingrong Liao ◽  
Nanrun Xiao ◽  
Xiaoqin Li
Keyword(s):  
Seismic Response ◽  
Fault Zone ◽  
Composite Structure ◽  
Composite Structures ◽  
Seismic Waves ◽  
Distribution Area ◽  
Damage Degree ◽  
Acceleration Amplification ◽  
Lining Structure ◽  
Composite Lining

The mechanical properties of high-toughness engineering cementitious composites (ECC) were tested, and a damage constitutive model of the materials was constructed. A new aseismic composite structure was then built on the basis of this model by combining aseismic joints, damping layers, traditional reinforced concrete linings, and ECC linings. A series of 3D dynamic-response numerical models considering the composite structure-surrounding rock-fault interaction were established to explore the seismic response characteristics and aseismic performance of the composite structures. The adaptability of the structures to the seismic intensity and direction was also discussed. Results showed that the ECC material displays excellent tensile and compressive toughness, with respective peak tensile and compressive strains of approximately 300- and 3-fold greater than those of ordinary concrete at the same strength grade. The seismic response law of the new composite lining structure was similar to that of the conventional composite structure. The lining in the fault zone and adjacent area showed obvious acceleration amplification responses, and the stress and displacement responses were fairly large. The lining in the fault zone was the weak part of the composite structures. Compared with the conventional aseismic composite structure, the new composite lining structure effectively reduced the acceleration amplification and displacement responses in the fault area. The damage degree of the new composite structure was notably reduced and the damage area was smaller compared with those of the conventional composite structure; these findings demonstrate that the former shows better aseismic effects than the latter. The intensity and direction of seismic waves influenced the damage of the composite structures to some extent, and the applicability of the new composite structure to lateral seismic waves is significantly better than that to axial waves. More importantly, under the action of different seismic intensities and directions, the damage degree and distribution area of the new composite structure were significantly smaller than those of the conventional composite lining structure.

Refraction of Fault-Zone Guided Seismic Waves

2011 ◽  
Vol 101 (4) ◽  
pp. 1674-1682 ◽  
Author(s):  
J. Wu ◽  
J. A. Hole
Keyword(s):  
Fault Zone ◽  
Seismic Waves

scholarly journals A numerical analysis of seismic waves for an anisotropic fault zone

2006 ◽  
Vol 58 (5) ◽  
pp. 569-582 ◽  
Author(s):  
Takeshi Nakamura ◽  
Hiroshi Takenaka
Keyword(s):  
Numerical Analysis ◽  
Fault Zone ◽  
Seismic Waves

Fault zone trapped seismic waves

1990 ◽  
Vol 80 (5) ◽  
pp. 1245-1271 ◽  
Author(s):  
Y.-G. Li ◽  
P. C. Leary
Keyword(s):  
Fault Zone ◽  
Seismic Waves ◽  
Fault Plane ◽  
Body Wave ◽  
Velocity Model ◽  
Trapped Waves ◽  
Low Velocity ◽  
Near Surface ◽  
San Andreas ◽  
Borehole Seismic

Abstract Two instances of fault zone trapped seismic waves have been observed. At an active normal fault in crystalline rock near Oroville in northern California, trapped waves were excited with a surface source and recorded at five near-fault borehole depths with an oriented three-component borehole seismic sonde. At Parkfield, California, a borehole seismometer at Middle Mountain recorded at least two instances of the fundamental and first higher mode seismic waves of the San Andreas fault zone. At Oroville recorded particle motions indicate the presence of both Love and Rayleigh normal modes. The Love-wave dispersion relation derived for an idealized wave guide with velocity structure determined by body-wave travel-time inversion yields seismograms of the fundamental mode that are consistent with the observed Love-wave amplitude and frequency. Applying a similar velocity model to the Parkfield observations, we obtain a good fit to the trapped wavefield amplitude, frequency, dispersion, and mode time separation for an asymmetric San Andreas fault zone structure—a high-velocity half-space to the southwest, a low-velocity fault zone, a transition zone containing the borehole seismometer, and an intermediate velocity half-space to the northeast. In the Parkfield borehole seismic data set, the locations (depth and offset normal to fault plane) of natural seismic events which do or do not excite trapped waves are roughly consistent with our model of the low velocity zone. We conclude that it is feasible to obtain near-surface borehole records of fault zone trapped waves. Because trapped modes are excited only by events close to the fault zone proper—thereby fixing these events in space relative to the fault—a wider investigation of possible trapped mode waveforms recorded by a borehole seismic network could lead to a much refined body-wave/tomographic velocity model of the fault and to a weighting of events as a function of offset from the fault plane. It is an open question whether near-surface sensors exist in a stable enough seismic environment to use trapped modes as an earth monitoring device.

Investigating the seismic imaging of faults using PS data from the Snøhvit field, Barents Sea, and forward seismic modelling 

2021 ◽  
Author(s):  
Jennifer Cunningham ◽  
Wiktor Weibull ◽  
Nestor Cardozo ◽  
David Iacopini
Keyword(s):  
Fault Zone ◽  
Seismic Data ◽  
Seismic Waves ◽  
Barents Sea ◽  
Incidence Angle ◽  
Seismic Signal ◽  
Fault Zones ◽  
Seismic Modelling ◽  
Systematic Improvement

<p>PS seismic data from the Snøhvit field are compared with forward seismic modelling to understand the effect of azimuthal separation and incidence angle on the imaging of faults. Two faults, one oriented oblique to the survey and one approximately parallel to the survey were chosen. Azimuthally separated W (source is W relative to receivers) and E (source E relative to receivers) data demonstrate that fault imaging is more affected by azimuth when the faults are oblique to the survey orientation, and W data image the faults better. Partial stack data show that with increasing incidence angle there is a systematic improvement in the quality of fault imaging in both the E and W data. In addition, the frequency content of seismic waves back-scattered from within and around fault zones is analysed in the Snøhvit data. Low-medium frequencies are dominant within fault zones, compared with higher frequencies in adjacent areas and haloes of medium frequencies surrounding the faults. Two synthetic experiments support the azimuth, incidence angle and frequency observations. In the first experiment, the fault is modelled as a planar discontinuity and the data were processed in the same way as the Snøhvit data (into separate azimuths and incidence angle stacks). The first experiment confirms a strengthening in the seismic signal from faults in the W data. This is due to the interaction of specular waves and diffractions which are more abundant in the W data. The second experiment had three parts modelling the fault zone with different layering complexity. It proved that frequencies in the fault and adjacent areas increase with fault zone complexity, and that the internal architecture of faults can impact the frequencies in the data adjacent to faults. </p>

Fault-zone attenuation of high-frequency seismic waves

1989 ◽  
Vol 16 (11) ◽  
pp. 1321-1324 ◽  
Author(s):  
Sam Blakeslee ◽  
Peter Malin ◽  
Marcos Alvarez
Keyword(s):  
Fault Zone ◽  
High Frequency ◽  
Seismic Waves ◽  
High Frequency Seismic Waves

Calcul de l'evolution de la permeabilite des reservoirs sedimentaries contenant des argiles; application a la zone de la faille de Bray (bassin de Paris)

2001 ◽  
Vol 172 (4) ◽  
pp. 427-436 ◽  
Author(s):  
Philippe Gouze ◽  
Riad Hassani ◽  
Dominique Bernard ◽  
Anne Coudrain-Ribstein
Keyword(s):  
Fluid Flow ◽  
Hydraulic Conductivity ◽  
Clay Minerals ◽  
Fault Zone ◽  
Weighting Coefficient ◽  
Permeability Evolution ◽  
Microstructural Characteristics ◽  
Porosity Evolution ◽  
Permeability Changes ◽  
Specific Contribution

Abstract We propose a model for simulating the changes in porosity and permeability caused by hydrothermal diagenesis in sedimentary aquifer where salinity, temperature and fluid flow vary in space and time. Such modifications of the hydrodynamic properties of the medium are bounded to geochemical reactions and groundwater flow. Fluid velocity is particularly low in deep reservoirs (typically less than 1 m/year). Then, the local equilibrium simplification, which is justified by a set of world-wide data of the chemical composition of groundwater, can be implemented toward straightforward transient calculations. In the model presented here, the coupled processes of fluid flow, temperature and chemical species transport are solved using well established methods. The originality of the model is the development carried on to predict the permeability evolution controlled by the mineral dissolution and precipitation. Usually to simulate permeability changes modelers use the classical porosity-permeability model based on statistical analyses of in situ or laboratory measurements. However, hydraulic conductivity changes are not controlled solely by porosity changes, but also depend on pore-scale structure transformations. Depending on the mineral type, the precipitation or dissolution of the same quantity of volumetric quantity will induce very different changes in the hydraulic conductivity. Principally clay minerals depict a wide range of atypical organisations of different microstructural characteristics of the porous media. The spatial distribution of these characteristics cannot be modelled at basin scale. Away from both too complicated and too unrealistically simplified approach, the model presented here is based on the calculation of the permeability evolution from the change in the mineral fraction due to mineral precipitation and dissolution. To simplify, the minerals are divided into two groups: clay minerals and non-clay minerals. The specific contribution of clay minerals is controlled by a single weighting coefficient. This coefficient is associated to the proportion of poorly connected porosity that characterize clay structure, albeit it is presently impossible to propose any quantitative relationship between the value of this parameter and the microstructural characteristics of the diagenetic clays. The model is tested here to simulate the evolution of the porosity and the permeability in a peculiar zone of the Paris Basin. The study area of several hundred meters large is inside the Dogger aquifer, close to the Bray fault zone where invasion of saline water from Triassic formation takes place. This zone is characterised by high thermal and salinity gradient as well as by the superposition of sub-horizontal regional flow and ascendant fault-controlled flow: it is an ideal case study for examining the importance of taking into account the specific contribution by clay minerals when computing permeability evolution. This study is proposed as a parameter sensibility analysis: - to compare the relative influence of the clay weighting coefficient, the temperature, the salinity, and the cementation exponent on the computed evolution of the permeability, - to discuss the consequences of the introduction of the clay weighting coefficient in comparison to the classical porosity - permeability evolution model, - to simulate various evolution scenarios of past and future thermal and geochemical constraints and their consequences on the evolution of the permeability changes in the Bray fault zone taking into account uncertainties on the value of the clay weighting coefficient and on the cementation exponent. Forty-one simulations of one million years were necessary to cover a large spectrum of the expected variations of each parameter. The results show that: - the local variation of the permeability depends on the time evolution of temperature and of salinity, and on the values of the cementation exponent of the porosity-permeability law and of the clay weighting coefficient. Within reasonable ranges of these four parameters, their influence on the permeability changes is of the same order of magnitude, - the influence of the clay weighting coefficient on the porosity evolution is negligible. Feedback effects of permeability evolution on the porosity evolution, through the change in the flow regime, is minor, - by the use of a classical model without a clay weighting coefficient, permeability and porosity present the same pattern of evolution: they both increase or decrease. By the use of the clay weighting coefficient, in some places the permeability and porosity can show opposite evolution. One increases when the other decreases even for low values of the coefficient, - in the vicinity of the fault, the model predict an increase of permeability independently of potential temperature and salinity modifications and whatever the clay mineral weighting coefficient is: Bray fault sealing is unlikely as long as head gradient is maintained in the fracture zone.

scholarly journals Attenuation of Seismic Waves along the Rokko Fault Zone

1997 ◽  
Vol 50 (2) ◽  
pp. 173-182 ◽  
Author(s):  
Shuichi NAKAMURA ◽  
Atsuki KUBO ◽  
Takahiro OHKURA ◽  
Toru OUCHI
Keyword(s):  
Fault Zone ◽  
Seismic Waves
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