Dynamic Triggering by Strong-Motion P and S Waves: Evidence from the 1999 Chi-Chi, Taiwan, Earthquake

Fischer, A.; Sammis, Charles G.; Chen, Youlin; Teng, Ta‐Liang

doi:10.1785/0120070155

Cited by 28 publications

(45 citation statements)

References 32 publications

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“…Second, the stress perturbation associated with the P wave is usually considered to be too small to cause much dynamic triggering at large distances. Recently, Fischer et al [2008a, 2008b] reported P wave‐triggered high‐frequency bursts in the near field during 1999 Mw 7.6 Chi‐Chi, Taiwan, earthquake and the 2004 Mw 6.0 Parkfield earthquake. They estimated a triggering threshold of ∼1 kPa.…”

Section: Discussionmentioning

confidence: 99%

Complex nonvolcanic tremor near Parkfield, California, triggered by the great 2004 Sumatra earthquake

et al. 2009

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[1] In several instances, the passing surface waves from large earthquakes have ignited nonvolcanic tremor (NVT) on major faults. Still, the mechanism of tremor and its reaction to the dynamic stressing from various body and surface waves is poorly understood. We examine tremor near Parkfield, California, beneath the San Andreas fault triggered by the Mw 9.2, 2004 Sumatra earthquake. The prolonged shaking produces the richest and the most varied observations of dynamically triggered tremor to date. The tremor appears in at least three distinct locations and shows activity pulsing with encouraging stress, as has been observed in other cases. The greatest amount of triggering and tremor modulation accompanies the long-period Love waves. Rayleigh waves, on the other hand, appear to be less effective in exciting tremor sources. Also, at times, the tremor stops before the surface waves are complete, at other times it continues quivering after the waves have passed. While tremor is found to be sensitive to small stress changes, there are times when stresses of comparable magnitudes do not trigger noticeable tremor. Some tremors in this NVT sequence appear to be associated with the passage of P waves, which is unusual and surprising given the small stresses they impart.

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Section: Discussionmentioning

confidence: 99%

Complex nonvolcanic tremor near Parkfield, California, triggered by the great 2004 Sumatra earthquake

et al. 2009

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“…There is direct evidence of brittle co‐seismic failure: small earthquakes in the shallow subsurface during shaking [ Fischer et al , 2008a, 2008b; Fischer and Sammis , 2009]. The largest of these events may cause brief extreme dynamic acceleration [ Aoi et al , 2008; Sleep and Ma , 2008].…”

Section: Stresses Within Seismically Damaged Regolithmentioning

confidence: 99%

Seismically damaged regolith as self-organized fragile geological feature

Sleep

2011

Geochem. Geophys. Geosyst.

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[1] The S-wave velocity in the shallow subsurface within seismically active regions self-organizes so that typical strong dynamic shear stresses marginally exceed the Coulomb elastic limit. The dynamic velocity from major strike-slip faults yields simple dimensional relations. The near-field velocity pulse is essentially a Love wave. The dynamic shear strain is the ratio of the measured particle velocity over the deep S-wave velocity. The shallow dynamic shear stress is this quantity times the local shear modulus. The dynamic shear traction on fault parallel vertical planes is finite at the free surface. Coulomb failure occurs on favorably oriented fractures and internally in intact rock. I obtain the equilibrium shear modulus by starting a sequence of earthquakes with intact stiff rock extending all the way to the surface. The imposed dynamic shear strain in stiff rock causes Coulomb failure at shallow depths and leaves cracks in it wake. Cracked rock is more compliant than the original intact rock. Cracked rock is also weaker in friction, but shear modulus changes have a larger effect. Each subsequent event causes additional shallow cracking until the rock becomes compliant enough that it just reaches Coulomb failure over a shallow depth range of tens to hundreds of meters. Further events maintain the material at the shear modulus as a function where it just fails. The formalism provided in the paper yields reasonable representation of the S-wave velocity in exhumed sediments near Cajon Pass and the San Fernando Valley of California. A general conclusion is that shallow rocks in seismically active areas just become nonlinear during typical shaking. This process causes transient changes in S-wave velocity, but not strong nonlinear attenuation of seismic waves. Wave amplitudes significantly larger than typical ones would strongly attenuate and strongly damage the rock.Components: 8800 words, 12 figures.

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“…[]; (9) Fischer et al . []. Red line shows the lower limit for triggering observations, along with the interpreted minimum value of aσ .…”

Section: Discussionmentioning

confidence: 99%

Frequency dependence of delayed and instantaneous triggering on laboratory and simulated faults governed by rate‐state friction

Elst

Savage

2015

JGR Solid Earth

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Earthquake triggering by transient stresses is commonly observed; however, some aspects remain unexplained. The first is the often-observed delay between the triggered earthquakes and the triggering waves, and the second is the unexpected effectiveness of transient stressing in the seismic frequency band. Previous theoretical and laboratory studies have suggested that seismic transients should have little impact on faults if the duration of the transient is smaller than the timescale for nucleation of slip. We reexamine the dynamics of stress triggering during stick-slip sliding on a laboratory fault and make three important observations that pertain to earthquake triggering. (1) Delayed triggering (clock advance) occurs for both bare granite surfaces and granular gouge prior to the onset of instantaneous triggering. (2) Triggering occurs much earlier in the stick-slip cycle than expected for a simple Coulomb stress threshold. (3) Shorter-period (higher stressing rate) pulses are more effective at triggering than longer-period pulses of the same stress amplitude. We use numerical simulations to show that rate-state friction can explain each of the observed features but not all three simultaneously. Only the Ruina slip law for state evolution, in which faults must slip to heal, can reproduce early-onset and stressing rate-dependent triggering. The laboratory and numerical experiments show that faults can remain relatively weak over much of the seismic cycle and that the triggered response depends on a competition between healing and weakening during triggered slip. Transient stressing at seismic frequencies may be more effective at triggering earthquakes than previously recognized.

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Dynamic Triggering by Strong-Motion P and S Waves: Evidence from the 1999 Chi-Chi, Taiwan, Earthquake

Cited by 28 publications

References 32 publications

Complex nonvolcanic tremor near Parkfield, California, triggered by the great 2004 Sumatra earthquake

Complex nonvolcanic tremor near Parkfield, California, triggered by the great 2004 Sumatra earthquake

Seismically damaged regolith as self-organized fragile geological feature

Frequency dependence of delayed and instantaneous triggering on laboratory and simulated faults governed by rate‐state friction

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