Manuel Rocha Medal Recipient Wave interaction with underground openings in fractured rock

Hildyard, M.W.

doi:10.1007/s00603-007-0158-3

Cited by 32 publications

(57 citation statements)

References 25 publications

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“…We use the full-waveform FD algorithm WAVE (Hildyard, 2007) to simulate wave propagation in 3D heterogeneous and isotropic media. The FD code computes the seismic wavefield on 4 equally-spaced, staggered orthogonal grid, where the variables stress and velocity are staggered at different points in time.…”

Section: Numerical Fd Modelmentioning

confidence: 99%

“…While much has been achieved with these methods, there are limitations such as the applicable frequency range, the types of fracture properties which can be studied, and non-uniform influences for example due to stress-field (e.g. Hildyard, 2007). The main restriction for EMM is that it is valid only when the dominant seismic wavelength of the propagating wave is much greater than the heterogeneity induced by the fractures; this is referred to as the long wavelength approximation (LWA).…”

Section: Introductionmentioning

confidence: 99%

“…Hildyard, 2007). DFM allows us to reduce many assumptions about the model and enables the solution to simulate the interaction of seismic waves with fractures systems more correctly.…”

Section: Introductionmentioning

confidence: 99%

“…To provide some insight into these fundamental questions, we study the development of SWS as a wave propagates through a fractured medium using the DFM approach. To do this, we model full-waveform seismic synthetics using the three-dimensional (3D) finite-difference (FD) algorithm WAVE (Hildyard, 2007) that models fracture networks as explicit discontinuity elements that can encapsulate individual fracture behaviour. By using the DFM approach we can explore the range of fracture properties that lead to effective anisotropy using heterogeneous yet coherent discontinuities by simulating the interaction of seismic waves with fractures.…”

Section: Introductionmentioning

confidence: 99%

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When do fractured media become seismically anisotropic? Some implications on quantifying fracture properties

Yousef

Angus

2016

Earth and Planetary Science Letters

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Fractures are pervasive features within the Earth's crust and have a significant influence on the multi-physical response of the subsurface. The presence of coherent fracture sets often leads to observable seismic anisotropy enabling seismic techniques to remotely locate and characterise fracture systems. In this study, we confirm the general scale-dependence of seismic anisotropy and provide new results specific to shear-wave splitting (SWS). We find that SWS develops under conditions when the ratio of wavelength to fracture size (λ S /d) is greater than 3, where Rayleigh scattering from coherent fractures leads to an effective anisotropy such that effective medium model (EMM) theory is qualitatively valid. When 1 < λ S /d < 3 there is a transition from Rayleigh to Mie scattering, where no effective anisotropy develops and hence the SWS measurements are unstable. When λ S /d < 1 we observe geometric scattering and begin to see behaviour similar to transverse isotropy. We find that seismic anisotropy is more sensitive to fracture density than fracture compliance ratio. More importantly, we observe that the transition from scattering to an effective anisotropic regime occurs over a propagation distance between 1 to 2 wavelengths depending on the fracture density and compliance ratio. The existence of a transition zone means that inversion of seismic anisotropy parameters based on EMM will be fundamentally biased. More importantly, we observe that linear slip EMM commonly used in inverting fracture properties is inconsistent with our results and leads to errors of approximately 400% in fracture spacing (equivalent to fracture density) and 60% in fracture compliance. Although EMM representations can yield reliable estimates of fracture orientation and spatial location, our results show that EMM representations will systematically fail in providing quantitatively accurate estimates of other physical fracture properties, such as fracture density and compliance. Thus more robust and accurate quantitative estimates of in situ fracture properties will require improvements to effective medium models as well as the incorporation of full-waveform inversion techniques.

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Section: Numerical Fd Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Hildyard, 2007). DFM allows us to reduce many assumptions about the model and enables the solution to simulate the interaction of seismic waves with fractures systems more correctly.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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When do fractured media become seismically anisotropic? Some implications on quantifying fracture properties

Yousef

Angus

2016

Earth and Planetary Science Letters

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“…However, hypogeous instabilities triggered by impulsive events were recorded during studies of collapse by the controlled explosion within mine areas (Phillips et al 1997;Yang et al 1998). Moreover, laboratory tests were performed on brittle materials to analyse possible correlations between acoustic emissions and observed microfracturing (Ganne et al 2007) and to derive theoretical models of wave interaction with opened fractures in rocks to be applied in numerical modelling (Tang 1997;Eberhardt et al 1998;Hildyard 2007).…”

Section: Introductionmentioning

confidence: 99%

Microseismicity within a karstified rock mass due to cracks and collapses as a tool for risk management

Lenti¹,

Martino

Paciello

et al. 2012

Nat Hazards

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Seismometer arrays have been widely applied to record collapse by controlled explosion in mines and caves. However, most underground failures are natural events, and because they can occur abruptly, underground failures represent a serious geological hazard. An accelerometric array installed on 4 September 2008 has been used to manage the geological risk of the Peschiera Springs drainage plant of Rome's aqueduct, which is located in the Central Apennines approximately 80 km from Rome, Italy. The plant occupies a karstified carbonatic slope that is extensively involved in gravitational deformations, which are responsible for underground failures such as cracks and collapses. To distinguish among different types of recorded events, an automated procedure was implemented based on the duration, peak of ground acceleration (PGA) and PGA variation in the recordings of the plant's accelerometric stations. The frequencies of earthquakes and micro-earthquakes due to underground failures are, in general, well correlated. Nevertheless, many underground failure sequences can be directly associated with the continuous deformations that affect the slope. The cumulative Arias intensity trend derived for the underground failures combined with the failure and earthquake frequencies enabled the definition of a control index (CI) that identifies alarming or emergency conditions. The CI can be used as a tool for managing the geological risk associated with the deformational processes that affect the drainage plant.

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The effects of joint spacing on transmission characteristics of stress waves through layered composite rock masses

Fan,

Shi,

Wang

et al. 2023

Num Anal Meth Geomechanics

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The effects of joint spacing on the transmission characteristics of stress waves through layered composite rock masses were investigated. First, a model of layered composite rock masses containing multiple parallel joints with different media in front of and behind the joints was introduced to study multiple reflections between joints. Second, wave transmission through layered composite rock masses was investigated and compared with wave transmission through traditional layered homogeneous rock masses. Finally, the effects of joint spacing and wave impedance ratio on particle velocity transmission coefficient were discussed. The results indicate that for wave propagation through rock masses with the same joint spacing, the onset time and amplitude of the transmitted wave in layered composite rock masses are smaller than those in layered homogeneous rock masses. For wave transmission through rock masses with the same nondimensional joint spacing, the onset time of the transmitted wave in the layered composite rock masses is similar to that in the layered homogeneous rock masses, while the amplitude of the transmitted wave in the layered composite rock masses is smaller than that in the layered homogeneous rock masses. In addition, the particle velocity transmission coefficient first increases and then decreases to be constant as the joint spacing increases, while it continues to increase as the wave impedance ratio increases for wave transmission through both layered composite rock masses and layered homogeneous rock masses.

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Manuel Rocha Medal Recipient Wave interaction with underground openings in fractured rock

Cited by 32 publications

References 25 publications

When do fractured media become seismically anisotropic? Some implications on quantifying fracture properties

When do fractured media become seismically anisotropic? Some implications on quantifying fracture properties

Microseismicity within a karstified rock mass due to cracks and collapses as a tool for risk management

The effects of joint spacing on transmission characteristics of stress waves through layered composite rock masses

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