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AGU: Journal of Geophysical Research, Solid Earth

 

Keywords

  • Baikal Rift Zone
  • refraction seismology
  • tomography
  • ray tracing
  • lower crustal intrusions

Index Terms

  • Tectonophysics: Continental tectonics: extensional
  • Tectonophysics: Rheology: general
  • Tectonophysics: Plate motions: present and recent
  • Tectonophysics: Plate motions: past
  • Seismology: Body waves
Abstract
Cited By (17)
 

Abstract

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, B00A06, 18 PP., 2009
doi:10.1029/2008JB006049

Remote triggering of tremor along the San Andreas Fault in central California

Zhigang Peng

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA

John E. Vidale

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

Aaron G. Wech

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

Robert M. Nadeau

Berkeley Seismological Laboratory, University of California, Berkeley, California, USA

Kenneth C. Creager

Department of Earth and Space Sciences, University of Washington, Seattle, Washington, USA

We perform a systematic survey of triggered tremor along the San Andreas Fault in central California for the 31 teleseismic earthquakes with Mw ≥ 7.5 since 2001. We identify 10 teleseismic events associated with clear triggered tremor. About 52% of the tremor is concentrated south of Parkfield near Cholame, where ambient tremor has been identified previously, and the rest is widely distributed in the creeping section of the San Andreas Fault north of Parkfield. Tremor is generally initiated and is in phase with the Love wave particle velocity. However, the pattern becomes complicated with the arrival of the Rayleigh waves, and sometimes tremor continues after the passage of the surface waves. We identify two cases in which tremor is triggered during the teleseismic PKP phase. These results suggest that while shear stress from the passage of the Love waves plays the most important role in triggering tremor in central California, other factors, such as dilatational stresses from the Rayleigh and P waves, also contribute. We also examine the ambient tremor occurrence rate before and after the teleseismic events and find a transient increase of stacked tremor rate during the passage of the teleseismic surface waves. This observation implies that the occurrence time of tremor is temporally advanced by the dynamic stresses of the teleseismic waves. The amplitude of the teleseismic waves correlates with the occurrence of triggered tremor, and the inferred tremor-triggering threshold is ∼2–3 kPa. The relatively low triggering threshold indicates that the effective stress at the tremor source region is very low, most likely due to near-lithostatic fluid pressure.

Received 30 August 2008; accepted 16 April 2009; published 18 July 2009.

Citation: Peng, Z., J. E. Vidale, A. G. Wech, R. M. Nadeau, and K. C. Creager (2009), Remote triggering of tremor along the San Andreas Fault in central California, J. Geophys. Res., 114, B00A06, doi:10.1029/2008JB006049.

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