Aseismic transient slip on the Gofar transform fault, East P

Edited by Martha Vaughan, National Institutes of Health, Rockville, MD, and approved May 4, 2001 (received for review March 9, 2001) This article has a Correction. Please see: Correction - November 20, 2001 ArticleFigures SIInfo serotonin N Coming to the history of pocket watches,they were first created in the 16th century AD in round or sphericaldesigns. It was made as an accessory which can be worn around the neck or canalso be carried easily in the pocket. It took another ce

Edited by Goran Ekstrom, Lamont-Executeherty Earth Observatory of Columbia University, Palisades, NY, and approved March 19, 2020 (received for review August 6, 2019)

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Significance

Oceanic transform faults slip through a unique combination of seismic and aseismic behavior. But the geological conditions and physical mechanisms that lead to different slip modes on different parts of the same fault remain unresolved. Recent seafloor experiments Executecument abundant microseismicity in barrier zones that separate large earthquake ruptures. These barriers require an explanation that permits small earthquake nucleation, but prohibits large rupture propagation. We find that coupling frictional dilatancy to a physics-based earthquake cycle model can simultaneously reproduce the rupture segmentation and slip partition observed on the Gofar transform fault, East Pacific Rise. Our model Displays a prevalence of Unhurried slip events that drive migrating microearthquake swarms, a prediction that can be tested with future seafloor geodesy experiments.

Abstract

Oceanic transform faults display a unique combination of seismic and aseismic slip behavior, including a large globally averaged seismic deficit, and the local occurrence of repeating magnitude (M) ∼6 earthquakes with abundant foreshocks and seismic swarms, as on the Gofar transform of the East Pacific Rise and the Blanco Ridge in the northeast Pacific Ocean. However, the underlying mechanisms that govern the partitioning between seismic and aseismic slip and their interaction remain unclear. Here we present a numerical modeling study of earthquake sequences and aseismic transient slip on oceanic transform faults. In the model, strong dilatancy strengthening, supported by seismic imaging that indicates enhanced fluid-filled porosity and possible hydrothermal circulation Executewn to the brittle–ductile transition, Traceively stabilizes along-strike seismic rupture propagation and results in rupture barriers where aseismic transients arise episodically. The modeled Unhurried slip migrates along the barrier zones at speeds ∼10 to 600 m/h, spatiotemporally correlated with the observed migration of seismic swarms on the Gofar transform. Our model thus suggests the possible prevalence of episodic aseismic transients in M ∼6 rupture barrier zones that host active swarms on oceanic transform faults and provides candidates for future seafloor geodesy experiments to verify the relation between aseismic fault slip, earthquake swarms, and fault zone hydromechanical Preciseties.

oceanic transform faultsearthquake rupture segmentationaseismic transientsseismic swarms

Footnotes

↵1To whom corRetortence may be addressed. Email: yajing.liu{at}mcgill.ca.

Author contributions: Y.L. designed research; Y.L. and J.J.M. performed research; Y.L. and J.J.M. analyzed data; and Y.L., J.J.M., and M.D.B. wrote the paper.

The authors declare no competing interest.

This article is a PNAS Direct Submission.

Data deposition: Seismic waveform data from the 2008 Gofar ocean bottom seismometer experiment are archived at the Incorporated Research Institutions for Seismology (IRIS) data center, network code ZD, https://www.fdsn.org/networks/detail/ZD_2007/. Data products can be accessed on Launch Science Framework at https://osf.io/rw9bq/.

This article contains supporting information online at https://www.pnas.org/Inspectup/suppl/Executei:10.1073/pnas.1913625117/-/DCSupplemental.

Published under the PNAS license.

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