气候变化领域集成服务门户(CCPortal): Acoustic evidence for a broad, hydraulically active damage zone surrounding the Alpine Fault, New Zealand

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DOI	10.1016/j.tecto.2020.228410
	Acoustic evidence for a broad, hydraulically active damage zone surrounding the Alpine Fault, New Zealand
	Jeppson T.N.; Tobin H.
发表日期	2020
ISSN	00401951
卷号	781
英文摘要	We present an analysis of the wireline sonic logs acquired through Alpine Fault hanging wall rocks during the second phase of the Deep Fault Drilling Project (DFDP-2). Due to inaccuracy in the initial tool-processed slowness logs, a more robust reprocessing of the data using the slowness–time coherence method was required. The reprocessing of the data yielded slowness logs that provide a significantly better estimate of compressional and shear slowness. The average slowness values of compressional and shear waves are 68 μs/ft and 110 μs/ft, respectively, corresponding to velocities of 4.5 km/s and 2.8 km/s, with some excursions related to fractures, borehole conditions, and tool settings, but no systematic downhole trends. The log values are compared to laboratory measurements of P- and S-wave velocity for samples of Alpine schist and mylonitic rocks to examine the scale dependence of the measurement. The average log velocity is 2 to 18% slower than the laboratory measurements due to the presence of mesoscale fractures that are present in situ but are not sampled at the laboratory scale. Using effective medium theory, we estimate the crack density in the hanging wall host rock to be ≤0.4. Comparison to field-scale seismic studies indicates that there is a broad (500–600 m wide) outer damage zone surrounding the intensely deformed inner damage zone of the Alpine Fault. This fractured outer zone facilitates fluid flow through the hanging wall and around the Alpine Fault. © 2020 Elsevier B.V.
关键词	Alpine Fault Deep Fault Drilling Project New Zealand Seismic velocity Wireline sonic log
英文关键词	Acoustic logging; Flow of fluids; Fracture; Infill drilling; Research laboratories; Seismic waves; Seismology; Shear waves; Velocity; Wave propagation; Alpine Faults; Drilling projects; New zealand; Seismic velocities; Wireline sonic; Shear flow; acoustic wave; fault zone; hanging wall; host rock; mylonite; P-wave; S-wave; schist; seismic velocity; wall rock; Alpine Fault Zone; New Zealand; South Island
语种	英语
来源期刊	Tectonophysics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/207780
作者单位	Geoscience Department, University of Wisconsin-Madison, 1215 W. Dayton St., Madison, WI 53706, United States
推荐引用方式 GB/T 7714	Jeppson T.N.,Tobin H.. Acoustic evidence for a broad, hydraulically active damage zone surrounding the Alpine Fault, New Zealand[J],2020,781.
APA	Jeppson T.N.,&Tobin H..(2020).Acoustic evidence for a broad, hydraulically active damage zone surrounding the Alpine Fault, New Zealand.Tectonophysics,781.
MLA	Jeppson T.N.,et al."Acoustic evidence for a broad, hydraulically active damage zone surrounding the Alpine Fault, New Zealand".Tectonophysics 781(2020).