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

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 Influence of Dry Beach on the Dynamic Stability of Ash Storage Field: A Numerical Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Fangtao She ◽  
Chang Liu ◽  
Xiangang Zhou ◽  
Changjun Qi ◽  
Jiulong Ding
Keyword(s):  
Fly Ash ◽  
Numerical Analysis ◽  
Seismic Waves ◽  
Northwest China ◽  
Standard Penetration Test ◽  
Storage Site ◽  
The Third ◽  
Storage Area ◽  
China Today ◽  
Horizontal Displacements

Ash storage sites are a commonly used method of disposing fly ash, a byproduct of coal combustion, in China today, and when it accumulates to a certain height, serious geological hazards may occur as a result of seismic activity. In this study, an in situ standard penetration test was carried out on a constructed ash storage site in Northwest China to evaluate the potential for liquefaction of alluvial fly ash within the site, and the results show that dynamic liquefaction can occur within a newly constructed three-stage subdam. A numerical analysis of the influence of dry beach length on the dynamic response of the primary dams and subdams and an assessment of the extent of dynamic liquefaction in the ash storage field were carried out using the Wenchuan seismic waves as input ground motion. Numerical results prove that the acceleration within the ash storage field is relatively low in the original breccias layer and gradually increases with height, with the peak acceleration occurring in the vicinity of the third subdam and a decreasing trend from the subdams towards the ash storage field. As the length of the dry beach increases, the Peak accelerations in the ash storage area occur near the third subdams at larger dry beach length. Meanwhile, the acceleration in the ash storage area close to the surface gradually increases, and, significantly, the range where higher accelerations occur also becomes larger. The maximum horizontal displacements at different dry beach lengths occur at the crest of the third subdam and in the adjacent ash storage area. As the length of the dry beach increases, the maximum horizontal displacements show a certain decrease, but they occur progressively further away from the third subdam, so that, under dynamic action, the dams become safer. The extent of liquefaction decreases at larger dry beach length and extends further away from the third subdam into the ash storage area. It is, therefore, recommended that the length of the dry beach should not be less than 150 m for this ash storage site.

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.

scholarly journals ANALYTICAL AND NUMERICAL ANALYSIS OF PLANE SEISMIC WAVES IN NONLINEAR VISCOELASTIC MEDIA

2016 ◽  
Author(s):  
Ж.Д. Тотиева
Keyword(s):  
Numerical Analysis ◽  
Nonlinear Response ◽  
Seismic Waves ◽  
Function Analysis ◽  
Nonlinear Damping ◽  
Physical Nonlinearity ◽  
Nonlinearity Parameter ◽  
Viscoelastic Media ◽  
Nonlinear Viscoelastic ◽  
Model Algorithm

Представлены модель, алгоритм и программный расчет нелинейного отклика среды на заданное возмущение для двухслойного полупространства. Теоретический подход основан на использовании функции Грина. Проведен анализ зависимости спектров синтетических акселерограмм от параметра нелинейности и частоты входного сигнала. Предложенная модель в полной мере учитывает физическую нелинейность: во‑первых, нелинейную связь «напряжение-деформация», во‑вторых, нелинейное затухание среды в зависимости от уровня деформации. Программный продукт может использоваться при прогнозировании нелинейного отклика грунта на ожидаемое расчетное землетрясение The model, algorithm and numerical results of the nonlinear response of the medium is presented. The theoretical approach is based on the use of the Green’s function. Analysis of the dependence of the spectra of synthetic accelerograms of the nonlinearity parameter and frequency of the input signal is carried out. The model takes into account the physical nonlinearity: at first, non-linear relationship «stress-strain», secondly, nonlinear damping medium depending on the strain level. The software can be used for predicting the nonlinear response of the ground to the expected estimated earthquake.

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>

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