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
+ Show Author Affiliations

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 Lab. (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, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 31 Vol. 113; ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)Copyright Statement
Country of Publication:
United States
Language:
English

References (24)

Inferring fault rheology from low-frequency earthquakes on the San Andreas: FAULT RHEOLOGY ON THE SAN ANDREAS journal November 2013
Influence of fortnightly tides on earthquake triggering at the East Pacific Rise at 9°50′N: Influence of Fortnightly Tides On journal March 2016
Evidence of earthquake triggering by the solid earth tides journal February 2009
Tidal triggering of microearthquakes on the Juan de Fuca Ridge journal October 2001
Why earthquakes correlate weakly with the solid Earth tides: Effects of periodic stress on the rate and probability of earthquake occurrence journal January 2003
Evidence for tidal triggering of earthquakes as revealed from statistical analysis of global data: TIDAL TRIGGERING OF EARTHQUAKES journal October 2002
Effects of shear velocity oscillations on stick-slip behavior in laboratory experiments journal January 2007
Pulse of the seafloor: Tidal triggering of microearthquakes at 9°50′N East Pacific Rise: TIDAL TRIGGERING AT 9°50′N EPR journal August 2007
Source parameters and time-dependent slip distributions of slow slip events on the Cascadia subduction zone from 1998 to 2008 journal January 2010
Precise tremor source locations and amplitude variations along the lower-crustal central San Andreas Fault: SAN ANDREAS TREMOR LOCATIONS/AMPLITUDES journal July 2010
Tremor reveals stress shadowing, deep postseismic creep, and depth-dependent slip recurrence on the lower-crustal San Andreas fault near Parkfield: TREMOR, STRESS, AND LOWER-CRUSTAL CREEP journal July 2011
Variety and spatial heterogeneity of tectonic tremor worldwide: TECTONIC TREMOR WORLDWIDE journal March 2012
Tidal triggering of low frequency earthquakes near Parkfield, California: Implications for fault mechanics within the brittle-ductile transition: TIDAL TRIGGERING OF LFES NEAR PARKFIELD journal May 2012
Low-frequency earthquakes in Shikoku, Japan, and their relationship to episodic tremor and slip journal July 2006
Tremor-tide correlations and near-lithostatic pore pressure on the deep San Andreas fault journal December 2009
Striations, duration, migration and tidal response in deep tremor journal July 2010
Low friction and fault weakening revealed by rising sensitivity of tremor to tidal stress journal April 2015
Non-volcanic tremor resulting from the combined effect of Earth tides and slow slip events journal September 2008
Nonvolcanic Deep Tremor Associated with Subduction in Southwest Japan journal May 2002
Earth Tides Can Trigger Shallow Thrust Fault Earthquakes journal November 2004
Widespread Triggering of Nonvolcanic Tremor in California journal January 2008
Tidal Modulation of Nonvolcanic Tremor journal January 2008
Asperity Model of an Earthquake: Static Problem journal March 2002
Slip on the San Andreas Fault at Parkfield, California, over Two Earthquake Cycles, and the Implications for Seismic Hazard journal September 2006

Cited By (5)

Squeezing Marsquakes out of groundwater journal January 2019
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
Modulation of Seismic Attenuation at Parkfield, Before and After the 2004 M 6 Earthquake journal June 2019

Similar Records

Related Subjects

58 GEOSCIENCES
faults
fortnightly tides
low-frequency earthquakes
tidal triggering