From crystal to crustal: petrofabric-derived seismic modelling of regional tectonics

Lloyd, Geoffrey E.; Halliday, J.; Butler, Robert W.; Casey, Martin; Kendall, J.‐M.; Wookey, James; Mainprice, David

doi:10.1144/sp360.4

Cited by 17 publications

(13 citation statements)

References 59 publications

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“…There is an increase in foliation intensity towards the fault core. The faster foliation-parallel velocities are controlled by the alignment of the platy phyllosilicate minerals (Lloyd et al, 2011b, a). Higher foliation-parallel permeability compared to flow perpendicular, as measured in the GTS samples, has been measured in previous studies (e.g., Faulkner and Rutter, 1998;Leclère et al, 2015;Wibberley and Shimamoto, 2003;Uehara and Shimamoto, 2004).…”

Section: Shear Zone Characterizationsupporting

confidence: 62%

Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock

Wenning¹,

Madonna²,

Haller³

et al. 2018

Preprint

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Abstract. This study characterizes the elastic and fluid flow properties systematically across a ductile-brittle fault zone in crystalline rock at the Grimsel Test Site underground research laboratory. Anisotropic seismic velocities and permeability measured every 0.1 m in the 0.7 m across the transition zone from the host Grimsel granodiorite to the fault core show that foliation-parallel p-and s-wave velocities systematically increase from the host rock towards the fault core, while permeability is reduced nearest to the fault core. The results suggest that although brittle deformation has persisted in the recent evolution, 5 antecedent ductile fabric continues to control the matrix elastic and fluid flow properties outside the fault core. The juxtaposition of the ductile strain zone next to the brittle zone, which is bounded inside the two mylonitic fault cores, causes a significant elastic, mechanical, and fluid flow heterogeneity, which has important implications for crustal deformation and fluid flow, and exploitation and use of geothermal energy and geologic waste storage. The results illustrate how physical characteristics of faults in crystalline rocks change in fault zones during the ductile to brittle transitions.

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Section: Shear Zone Characterizationsupporting

confidence: 62%

Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock

Wenning¹,

Madonna²,

Haller³

et al. 2018

Preprint

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“…Typically, ray‐tracing methods are applied at a much larger (crustal) scale, modeling a small number of internally homogeneous structures (layers), each of which may well have been assigned anisotropic properties derived from small‐scale petrofabric analysis as discussed by Lloyd et al . [, ].…”

Section: Discussionmentioning

confidence: 99%

“…Seismic anisotropy is commonly assumed to be dominantly affected by the petrofabrics, such as the crystallographic preferred orientation (CPO), of volumetrically significant mineral phases, such as quartz in the crust and olivine in the upper mantle [e.g., Nicolas and Christensen, 1987;Holbrook et al, 1992;Ismail and Mainprice, 1998;Tatham et al, 2008;Lloyd et al, 2011aLloyd et al, , 2011b, or less volumetrically dominant but highly anisotropic minerals like mica [Llana-Funez and Brown, 2012;Cholach et al, 2005]. A conventional method to investigate seismic anisotropy from rock samples involves the calculation of Voigt-Reuss-Hill (VRH) averages of the elastic tensor from the single crystal stiffness matrix of the rock forming minerals, weighted by CPO and modal composition [e.g., Mainprice, 1990;Mainprice and Humbert, 1993;Erdman et al, 2013;Llana-Funez et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

A novel EBSD‐based finite‐element wave propagation model for investigating seismic anisotropy: Application to Finero Peridotite, Ivrea‐Verbano Zone, Northern Italy

Zhong

Frehner

Kunze

et al. 2014

Geophysical Research Letters

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A novel electron backscatter diffraction (EBSD) ‐based finite‐element (FE) wave propagation simulation is presented and applied to investigate seismic anisotropy of peridotite samples. The FE model simulates the dynamic propagation of seismic waves along any chosen direction through representative 2D EBSD sections. The numerical model allows separation of the effects of crystallographic preferred orientation (CPO) and shape preferred orientation (SPO). The obtained seismic velocities with respect to specimen orientation are compared with Voigt‐Reuss‐Hill estimates and with laboratory measurements. The results of these three independent methods testify that CPO is the dominant factor controlling seismic anisotropy. Fracture fillings and minor minerals like hornblende only influence the seismic anisotropy if their volume proportion is sufficiently large (up to 23%). The SPO influence is minor compared to the other factors. The presented FE model is discussed with regard to its potential in simulating seismic wave propagation using EBSD data representing natural rock petrofabrics.

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“…[], and Lloyd et al . [, ] introduced a rock recipe configuration to address interpretation of seismic anisotropy in the ductile middle and lower crust. The premise of this methodology is to measure mineral CPO for common rock‐forming minerals present in middle and lower crust and vary their modal mineral composition, in order to explore the relative contribution to seismic anisotropy from individual minerals and the resulting strength and geometry of seismic anisotropy.…”

Section: Seismic Properties Of the Continental Crust From The Mineralmentioning

confidence: 99%

Seismic properties and anisotropy of the continental crust: Predictions based on mineral texture and rock microstructure

Almqvist

Mainprice

2017

Reviews of Geophysics

164

127

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Progress in seismic methodology and ambitious large‐scale seismic projects are enabling high‐resolution imaging of the continental crust. The ability to constrain interpretations of crustal seismic data is based on laboratory measurements on rock samples and calculations of seismic properties. Seismic velocity calculations and their directional dependence are based on the rock microfabric, which consists of mineral aggregate properties including crystallographic preferred orientation (CPO), grain shape and distribution, grain boundary distribution, and misorientation within grains. Single‐mineral elastic constants and density are crucial for predicting seismic velocities, preferably at conditions that span the crust. However, high‐temperature and high‐pressure elastic constant data are not as common as those determined at standard temperature and pressure (STP; atmospheric conditions). Continental crust has a very diverse mineral composition; however, a select number of minerals appear to dominate seismic properties because of their high‐volume fraction contribution. Calculations of microfabric‐based seismic properties and anisotropy are performed with averaging methods that in their simplest form takes into account the CPO and modal mineral composition, and corresponding single crystal elastic constants. More complex methods can take into account other microstructural characteristics, including the grain shape and distribution of mineral grains and cracks and pores. Dynamic or active wave propagation schemes have recently been developed, which offer a complementary method to existing static averaging methods generally based on the use of the Christoffel equation. A challenge for the geophysics and rock physics communities is the separation of intrinsic factors affecting seismic anisotropy, due to properties of crystals within a rock and apparent sources due to extrinsic factors like cracks, fractures, and alteration. This is of particular importance when trying to deduce crustal composition and the state of deformation from seismic parameters.

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From crystal to crustal: petrofabric-derived seismic modelling of regional tectonics

Cited by 17 publications

References 59 publications

Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock

Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock

A novel EBSD‐based finite‐element wave propagation model for investigating seismic anisotropy: Application to Finero Peridotite, Ivrea‐Verbano Zone, Northern Italy

Seismic properties and anisotropy of the continental crust: Predictions based on mineral texture and rock microstructure

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