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DOI	10.1016/j.epsl.2019.115970
	Temporal and spatial variations in seismic anisotropy and VP/VS ratios in a region of slow slip
	Zal H.J.; Jacobs K.; Savage M.K.; Yarce J.; Mroczek S.; Graham K.; Todd E.K.; Nakai J.; Iwasaki Y.; Sheehan A.; Mochizuki K.; Wallace L.; Schwartz S.; Webb S.; Henrys S.
发表日期	2020
ISSN	0012821X
卷号	532
英文摘要	In September 2014, a five week long slow slip event (SSE) occurred near Gisborne at the northern Hikurangi subduction zone, New Zealand, and was recorded by offshore instruments deployed by the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) project. Up to 25 cm of slip occurred directly below the HOBITSS array. We calculate shear wave splitting (SWS) and VP/VS ratios for event-station pairs on HOBITSS ocean bottom seismometers and onshore GeoNet seismic stations to determine the relationship in time and space between slow slip and these seismic properties. Spatial averaging of SWS fast azimuths yields trench-perpendicular fast azimuths in some areas, suggesting that compressive stress from plate convergence closes microcracks and controls anisotropy in the upper-plate. Variations from the trench perpendicular directions are observed near a subducting seamount, with directions closely resembling fracture and fault patterns created by subducting seamounts previously observed in both laboratory and field experiments. Temporal variations in fast azimuths are observed at three stations, two of which are located above the seamount, suggesting measurable variations in stress orientations. During the SSE, median VP/VS measurements across all offshore stations increase from 1.817 to 1.894 and SWS delay times decrease from 0.178 s to 0.139 s (both changes are significant within 95% confidence intervals). Temporal variations in VP/VS and delay time are consistent with fluid pressurization below a permeability barrier and movement of fluids during the rupture of a slow-slip patch. © 2019 Elsevier B.V.
关键词	anisotropy New Zealand seamount shear wave splitting slow slip subduction zones
英文关键词	Anisotropy; Microcracks; Offshore oil well production; Seismology; Shear flow; Shear waves; Submarine geology; New zealand; seamount; Shear wave splitting; slow slip; Subduction zones; Slow wave structures; microcrack; ocean bottom seismometer; P-wave; plate convergence; S-wave; seamount; seismic anisotropy; slip rate; spatiotemporal analysis; subduction zone; wave splitting; New Zealand
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202997
作者单位	Victoria University of Wellington, Wellington, New Zealand; GNS Science, Lower Hutt, New Zealand; Department of Geological Sciences, University of Colorado Boulder, Boulder, CO, United States; Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, United States; Department of Geology, University of Otago, Dunedin, New Zealand; Earthquake Research Institute, University of Tokyo, Tokyo, Japan; Institute for Geophysics, University of Texas, Austin, TX, United States; Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA, United States; Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, United States
推荐引用方式 GB/T 7714	Zal H.J.,Jacobs K.,Savage M.K.,et al. Temporal and spatial variations in seismic anisotropy and VP/VS ratios in a region of slow slip[J],2020,532.
APA	Zal H.J..,Jacobs K..,Savage M.K..,Yarce J..,Mroczek S..,...&Henrys S..(2020).Temporal and spatial variations in seismic anisotropy and VP/VS ratios in a region of slow slip.Earth and Planetary Science Letters,532.
MLA	Zal H.J.,et al."Temporal and spatial variations in seismic anisotropy and VP/VS ratios in a region of slow slip".Earth and Planetary Science Letters 532(2020).