Migrating tremors illuminate complex deformation beneath the seismogenic san andreas fault

ABSTRACT The San Andreas fault is one of the most extensively studied faults in the world, yet its physical character and deformation mode beneath the relatively shallow

earthquake-generating portion remain largely unconstrained. Tectonic ‘non-volcanic’ tremor, a recently discovered seismic signal1 probably generated by shear slip on the deep extension of

some major faults2,3,4, can provide new insight into the deep fate of such faults, including that of the San Andreas fault near Parkfield, California5. Here I examine continuous seismic data

from mid-2001 to 2008, identifying tremor and decomposing the signal into different families of activity based on the shape and timing of the waveforms at multiple stations6. This approach

allows differentiation between activities from nearby patches of the deep fault and begins to unveil rich and complex patterns of tremor occurrence. I find that tremor exhibits nearly

continuous migration, with the most extensive episodes propagating more than 20 kilometres along fault strike at rates of 15–80 kilometres per hour. This suggests that the San Andreas fault

remains a localized through-going structure, at least to the base of the crust, in this area. Tremor rates and recurrence behaviour changed markedly in the wake of the 2004 magnitude-6.0

Parkfield earthquake6,7, but these changes were far from uniform within the tremor zone, probably reflecting heterogeneous fault properties and static and dynamic stresses decaying away from

the rupture. The systematic recurrence of tremor demonstrated here suggests the potential to monitor detailed time-varying deformation on this portion of the deep San Andreas fault,

deformation which unsteadily loads the shallower zone that last ruptured in the 1857 magnitude-7.9 Fort Tejon earthquake8. Access through your institution Buy or subscribe This is a preview

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ADDITIONAL ACCESS OPTIONS: * Log in * Learn about institutional subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS LINKING THE SCALING OF TREMOR

AND SLOW SLIP NEAR PARKFIELD, CA Article Open access 03 October 2022 TREMOR ALONG THE DEAD SEA TRANSFORM REMOTELY TRIGGERED BY THE 2023 _M__W_7.6 KAHRAMANMARAŞ EARTHQUAKE Article Open access

28 February 2024 REPEATING EARTHQUAKES AND GROUND DEFORMATION REVEAL THE STRUCTURE AND TRIGGERING MECHANISMS OF THE PERNICANA FAULT, MT. ETNA Article Open access 09 June 2021 REFERENCES *

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Soc. Am._ 96 S283–S303 10.1785/0120050820 (2006) Article  Google Scholar  Download references ACKNOWLEDGEMENTS I thank T. Ryberg and C. Haberland for sharing data from temporary arrays GFZ1,

GFZ2 and GFZ3. G. Fuis assisted with permitting and installation of these stations and instruments were provided by GIPP of GFZ. W. Ellsworth and J. Murphy installed temporary stations at

the Vogel site. I thank R. Nadeau for sharing his tremor catalogue. The HRSN is operated by UC-Berkeley, and seismic data was provided through the NCEDC. I thank J. Vidale, J. Hardebeck and

J. Gomberg for reviewing various forms of this manuscript. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * US Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025, USA

, David R. Shelly Authors * David R. Shelly View author publications You can also search for this author inPubMed Google Scholar CORRESPONDING AUTHOR Correspondence to David R. Shelly.

ETHICS DECLARATIONS COMPETING INTERESTS The author declares no competing financial interests. SUPPLEMENTARY INFORMATION SUPPLEMENTARY INFORMATION This file contains Supplementary Figures

S1-S6 with Legends and Supplementary Table S1. (PDF 1249 kb) POWERPOINT SLIDES POWERPOINT SLIDE FOR FIG. 1 POWERPOINT SLIDE FOR FIG. 2 POWERPOINT SLIDE FOR FIG. 3 POWERPOINT SLIDE FOR FIG. 4

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_Nature_ 463, 648–652 (2010). https://doi.org/10.1038/nature08755 Download citation * Received: 29 July 2009 * Accepted: 07 December 2009 * Issue Date: 04 February 2010 * DOI:

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