Fracture Shape and Orientation Contributions to P-Wave Velocity and Anisotropy of Alpine Fault Mylonites
- Publication type:
- Journal article
- Metadata:
-
- Autoren
- Jirapat Charoensawan
- Ludmila Adam
- Michael Ofman
- Virginia Toy
- Jonathan Simpson
- Xin Zhong
- Bernhard Schuck
- Autoren-URL
- https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=fis-test-1&SrcAuth=WosAPI&KeyUT=WOS:000647023900001&DestLinkType=FullRecord&DestApp=WOS_CPL
- DOI
- 10.3389/feart.2021.645532
- eISSN
- 2296-6463
- Externe Identifier
- Clarivate Analytics Document Solution ID: RX2BE
- Zeitschrift
- FRONTIERS IN EARTH SCIENCE
- Schlüsselwörter
- P-wave velocity
- anisotropy
- Alpine Fault
- fracture
- electron backscattered diffraction
- numerical modeling
- synchrotron X-ray microtomography
- Artikelnummer
- ARTN 645532
- Datum der Veröffentlichung
- 2021
- Status
- Published
- Titel
- Fracture Shape and Orientation Contributions to P-Wave Velocity and Anisotropy of Alpine Fault Mylonites
- Sub types
- Article
- Ausgabe der Zeitschrift
- 9
Data source: Web of Science (Lite)
- Other metadata sources:
-
- Abstract
- <jats:p>P-wave anisotropy is significant in the mylonitic Alpine Fault shear zone. Mineral- and texture-induced anisotropy are dominant in these rocks but further complicated by the presence of fractures. Electron back-scattered diffraction and synchrotron X-ray microtomography (micro-CT) data are acquired on exhumed schist, protomylonite, mylonite, and ultramylonite samples to quantify mineral phases, crystal preferred orientations, microfractures, and porosity. The samples are composed of quartz, plagioclase, mica and accessory garnet, and contain 3–5% porosity. Based on the micro-CT data, the representative pore shape has an aspect ratio of 5:2:1. Two numerical models are compared to calculate the velocity of fractured rocks: a 2D wave propagation model, and a differential effective medium model (3D). The results from both models have comparable pore-free fast and slow velocities of 6.5 and 5.5 km/s, respectively. Introducing 5% fractures with 5:2:1 aspect ratio, oriented with the longest axes parallel to foliation decreases these velocities to 6.3 and 5.0 km/s, respectively. Adding both randomly oriented and foliation-parallel fractures hinders the anisotropy increase with fracture volume. The anisotropy becomes independent of porosity when 80% of fractures are randomly oriented. Modeled anisotropy in 2D and 3D are different for similar fracture aspect ratios, being 30 and 15%, respectively. This discrepancy is the result of the underlying assumptions and limitations. Our numerical results explain the effects that fracture orientations and shapes have on previously published field- and laboratory-based studies. Through this numerical study, we show how mica-dominated, pore-free P-wave anisotropy compares to that of fracture volume, shape and orientation for protolith and shear zone rocks of the Alpine Fault.</jats:p>
- Autoren
- Jirapat Charoensawan
- Ludmila Adam
- Michael Ofman
- Virginia Toy
- Jonathan Simpson
- Xin Zhong
- Bernhard Schuck
- DOI
- 10.3389/feart.2021.645532
- eISSN
- 2296-6463
- Zeitschrift
- Frontiers in Earth Science
- Online publication date
- 2021
- Status
- Published online
- Herausgeber
- Frontiers Media SA
- Herausgeber URL
- http://dx.doi.org/10.3389/feart.2021.645532
- Datum der Datenerfassung
- 2021
- Titel
- Fracture Shape and Orientation Contributions to P-Wave Velocity and Anisotropy of Alpine Fault Mylonites
- Ausgabe der Zeitschrift
- 9
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