气候变化领域集成服务门户(CCPortal): Frictional Strengths of Subduction Thrust Rocks in the Region of Shallow Slow Earthquakes

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DOI	10.1029/2019JB018888
	Frictional Strengths of Subduction Thrust Rocks in the Region of Shallow Slow Earthquakes
	Phillips N.J.; Belzer B.; French M.E.; Rowe C.D.; Ujiie K.
发表日期	2020
ISSN	21699313
卷号	125 期号:3
英文摘要	Earthquakes are expected to nucleate within velocity-weakening materials; however, at the updip limit of the subduction seismogenic zone, the principal lithologies exhibit velocity-strengthening behavior. At an exhumed analogue for present-day subduction at Nankai (the Mugi Mélange, Japan) two examples of paleoseismic features occur within altered basalts, suggesting that they may be velocity-weakening. We shear altered basalt and shale matrix from the mélange in the triaxial saw cut configuration at in situ conditions of deformation (Pc = 120 MPa, T = 150 °C) for two pore fluid factors (λ = 0.36, 0.7). The shale matrix exhibits a coefficient of friction between 0.4 and 0.5, and velocity-strengthening behavior. Altered basalt exhibits Byerlee friction and velocity-weakening behavior. In most experiments deformation was partitioned into Riedel shears, which have a lower percentage of clasts, clast size distributions with higher fractal dimensions, and shape factors indicating rounder clasts compared to the matrix between Riedel shears. We hypothesize that earthquakes preferentially nucleate within altered basalt at the updip limit of the seismogenic zone. More complex forms of deformation (e.g., shallow very low frequency earthquakes) may occur by mixing velocity-weakening altered basalt into the velocity-strengthening shale matrix. In subduction zones where the matrix is composed of shale, this complex behavior is limited to shallow depths (T < ~250 °C), above the updip transition to velocity-weakening behavior for the matrix. Altered basalt is a ubiquitous subducting material, and future studies on its behavior through a range of subduction zone conditions are required for a full understanding of the mechanical behavior of subduction zones. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	earthquake nucleation; friction; mélange; rate-and-state; rheology; slow earthquakes
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/187910
作者单位	Department of Earth and Planetary Sciences, McGill University, Montreal, QC, Canada; Department of Earth, Environmental and Planetary Sciences, William Marsh Rice University, Houston, TX, United States; Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
推荐引用方式 GB/T 7714	Phillips N.J.,Belzer B.,French M.E.,et al. Frictional Strengths of Subduction Thrust Rocks in the Region of Shallow Slow Earthquakes[J],2020,125(3).
APA	Phillips N.J.,Belzer B.,French M.E.,Rowe C.D.,&Ujiie K..(2020).Frictional Strengths of Subduction Thrust Rocks in the Region of Shallow Slow Earthquakes.Journal of Geophysical Research: Solid Earth,125(3).
MLA	Phillips N.J.,et al."Frictional Strengths of Subduction Thrust Rocks in the Region of Shallow Slow Earthquakes".Journal of Geophysical Research: Solid Earth 125.3(2020).