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Title: Fortnightly modulation of San Andreas tremor and low-frequency earthquakes

Journal Article · · Proceedings of the National Academy of Sciences of the United States of America
 [1];  [2];  [3];  [2]
  1. United States Geological Survey, Pasadena, CA (United States). Earthquake Science Center
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Geophysics Group
  3. United States Geological Survey, Pasadena, CA (United States). Volcanic Science Center
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Earth tides modulate tremor and low-frequency earthquakes (LFEs) on faults in the vicinity of the brittle-ductile (seismic-aseismic) transition. Our response to the tidal stress carries otherwise inaccessible information about fault strength and rheology. We analyze the LFE response to the fortnightly tide, which modulates the amplitude of the daily tidal stress over a 14-d cycle. LFE rate is highest during the waxing fortnightly tide, with LFEs most strongly promoted when the daily stress exceeds the previous peak stress by the widest margin. This pattern implies a threshold failure process, with slip initiated when stress exceeds the local fault strength. Furthermore, variations in sensitivity to the fortnightly modulation may reflect the degree of stress concentration on LFE-producing brittle asperities embedded within an otherwise aseismic fault.

Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC52-06NA25396
OSTI ID:
1340914
Report Number(s):
LA-UR-15-27728
Journal Information:
Proceedings of the National Academy of Sciences of the United States of America, Vol. 113, Issue 31; ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 25 works
Citation information provided by
Web of Science

References (24)

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Source parameters and time-dependent slip distributions of slow slip events on the Cascadia subduction zone from 1998 to 2008 journal January 2010
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Slip on the San Andreas Fault at Parkfield, California, over Two Earthquake Cycles, and the Implications for Seismic Hazard journal September 2006
Non-volcanic tremor resulting from the combined effect of Earth tides and slow slip events journal September 2008
Variety and spatial heterogeneity of tectonic tremor worldwide: TECTONIC TREMOR WORLDWIDE journal March 2012
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Evidence of earthquake triggering by the solid earth tides journal February 2009
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Earth Tides Can Trigger Shallow Thrust Fault Earthquakes journal November 2004
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Low friction and fault weakening revealed by rising sensitivity of tremor to tidal stress journal April 2015
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Cited By (4)

Loading‐Induced Earth's Stress Change Over Time journal May 2018
Variability in Io's Volcanism on Timescales of Periodic Orbital Changes journal June 2019
Squeezing Marsquakes Out of Groundwater journal June 2019
Squeezing Marsquakes out of groundwater journal January 2019

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Related Subjects

58 GEOSCIENCES
faults
low-frequency earthquakes
tidal triggering
fortnightly tides