期刊
NATURE GEOSCIENCE
卷 12, 期 6, 页码 475-+出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/s41561-019-0367-x
关键词
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资金
- Royal Society of New Zealand Marsden Fund grant [15-GNS-026]
- MBIE Endeavour Fund grant
- NSF [OCE-1334654, 1333311, 1332875, 1333025]
- ERI JURP [2013-B-09]
- Directorate For Geosciences [1332875] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Ocean Sciences [1333025] Funding Source: National Science Foundation
- Directorate For Geosciences
- Division Of Ocean Sciences [1333311] Funding Source: National Science Foundation
- Division Of Ocean Sciences [1332875] Funding Source: National Science Foundation
Slow slip events are part of a spectrum of aseismic processes that relieve tectonic stress on faults. Their spatial distribution in subduction zones has been linked to perturbations in fluid pressure within the megathrust shear zone and subducting oceanic crust. However, physical observations of temporal fluid pressure fluctuations through slow slip cycles remain elusive. Here, we use earthquake focal mechanisms recorded on an ocean-bottom seismic network to show that crustal stresses and fluid pressures within subducting oceanic crust evolve before and during slow slip events. Specifically, we observe that the retrieved stress ratio, which describes the relative magnitudes of the principal compressive stresses, systematically decreases before slow slip events in New Zealand's northern Hikurangi subduction zone, and subsequently increases during the evolution of each slow slip event. We propose that these changes represent the accumulation and release of fluid pressure within overpressured subducting oceanic crust, the episodicity of which may influence the timing of slow slip event occurrence on subduction megathrusts. This work contributes an improved understanding of the physical driving forces underlying slow subduction earthquakes, and a potential means by which to monitor stress and fluid pressure accumulation in such regions.
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