Summary of triggering of non-volcanic tremor in Cascadia
Justin Rubinstein Justin Rubinstein
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Tremor is Modulated by Love WavesTremor is Modulated by Love Waves
How things work*Love
waves
Earthquake in Alaska
Tremor Modulated by Stress AmplitudeTremor Modulated by Stress Amplitude
Rubinstein et al, 2007
Rubinstein et al, submitted
Does Amplitude Control Triggering?
Rubinstein et al, 2009
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Peng et al, submitted
Does Amplitude Control Triggering
in Parkfield?
Peng et al, in prep
Does Amplitude Control Triggering
in Taiwan?
Tremor correlates with tides
Shelly et al., (2007)Shelly et al., (2007)
Recordings of 3 ETS episodesRecordings of 3 ETS episodes
Tremor“Noise”
Tremor spectra for the 5 arraysTremor spectra for the 5 arrays
Rubinstein et al, 2008
Amplitude variation with 12.4-hr periodAmplitude variation with 12.4-hr period
12.4-hr tides 30% effect24-hr probably similar magnitude
Summary & ConclusionsSummary & Conclusions
• Tremor is triggered by very small dynamic Tremor is triggered by very small dynamic stresses from teleseismic EQs (10s of KPa)stresses from teleseismic EQs (10s of KPa)
• Tremor is modulated by the very small stresses Tremor is modulated by the very small stresses of the earth and ocean tides (~10KPa)of the earth and ocean tides (~10KPa)
• Ambient stress ~10Ambient stress ~1055 times stronger times stronger
• Tremor is occurring on faults that are very Tremor is occurring on faults that are very close to failureclose to failure– Fluids? Low Friction? Just Close to Failure?Fluids? Low Friction? Just Close to Failure?
Triggered Tremor = ETS TremorTriggered Tremor = ETS Tremor
Tremor vs aligned 12.4-hr bumpsTremor vs aligned 12.4-hr bumps
Array SO for 2004
PA for 2005
BS for 2007