气候变化领域集成服务门户(CCPortal): Seismic Anisotropy and Its Impact on Imaging the Shallow Alpine Fault: An Experimental and Modeling Perspective

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DOI	10.1029/2019JB019029
	Seismic Anisotropy and Its Impact on Imaging the Shallow Alpine Fault: An Experimental and Modeling Perspective
	Adam L.; Frehner M.; Sauer K.; Toy V.; Guerin-Marthe S.
发表日期	2020
ISSN	21699313
卷号	125 期号:8
英文摘要	The transpressional Alpine Fault in New Zealand has created a thick shear zone with associated highly anisotropic rocks. Low seismic velocity zones and high seismic reflectivity are recorded in the Alpine Fault Zone, but no study has explored the underlying physical rock parameters of the shallow crust that control these observations. Protomylonites are the volumetrically dominant lithology of the fault zone. Here we combine experimental measurements of P-wave speeds with numerical models of elastic wave anisotropy of protomylonite samples to explore how the fault zone can be seismically imaged. Numerical models that account for the porosity-free real samples' fabric elastic tensors from electron backscatter diffraction (EBSD) are calculated by MTEX and a finite element model (FEM), while microfractures are modeled with differential effective medium (DEM) theory. At effective pressures representative of the Alpine Fault brittle zone, experimental wave speeds are lower than those predicted by MTEX/FEM. A possible DEM model suggests that a combination of random and aligned microfractures with aspect ratios increasing with pressure can explain the experimental wave speeds for pressures <70 MPa. Such microporosity in the form of foliation- and mica basal plane-parallel microfractures and grain boundaries is validated with synchrotron X-ray microtomography and transmission electron microscopy (TEM) images. Finally, by modeling anisotropy of seismic reflection coefficients with angle of incidence, we demonstrate that the high reflectivity and low-velocity zone (LVZ) observed at the Alpine Fault can only be explained if this microporosity is accounted for throughout the brittle fault zone, even at depths of 7–10 km. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	Alpine Fault; anisotropy; EBSD; fractures; modeling; seismic waves
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187683
作者单位	School of Environment, University of Auckland, Auckland, New Zealand; Department of Earth Sciences, ETH Zürich, Zürich, Switzerland; Department of Geology, University of Otago, Dunedin, New Zealand; Institut für Geowissenschaften Johannes Gutenberg Universität-Mainz, Mainz, Germany; Department of Earth Sciences, Durham University, Durham, United Kingdom
推荐引用方式 GB/T 7714	Adam L.,Frehner M.,Sauer K.,et al. Seismic Anisotropy and Its Impact on Imaging the Shallow Alpine Fault: An Experimental and Modeling Perspective[J],2020,125(8).
APA	Adam L.,Frehner M.,Sauer K.,Toy V.,&Guerin-Marthe S..(2020).Seismic Anisotropy and Its Impact on Imaging the Shallow Alpine Fault: An Experimental and Modeling Perspective.Journal of Geophysical Research: Solid Earth,125(8).
MLA	Adam L.,et al."Seismic Anisotropy and Its Impact on Imaging the Shallow Alpine Fault: An Experimental and Modeling Perspective".Journal of Geophysical Research: Solid Earth 125.8(2020).