Precursory Rise of P-Wave Attenuation before the 2004 Parkfield Earthquake

Chun, Kin-Yip; Yuan, Qiang; Henderson, Gary

doi:10.1785/0120090104

Cited by 8 publications

(16 citation statements)

References 43 publications

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“…Chun et al . [] observe a larger than expected precursory t * at one station to the southwest of the fault trace. They suggest that this may be due to greater damage to the southwest as proposed by Li et al .…”

Section: Discussionmentioning

confidence: 67%

“…It is also worth noting that Chun et al . [], using surface rather than borehole stations, observe postseismic changes in attenuation associated with the 2004 M6.0 Parkfield earthquake, with a time lag occurring before the observed peak attenuation value. Attenuation is observed to be at a maximum at partial saturation (e.g., Winkler and Nur []).…”

Section: Discussionmentioning

confidence: 95%

“…Changes in seismic attenuation at this time have previously been noted by Chun et al . [] and Allmann and Shearer [ ]. In this study, a number of clusters of repeating earthquakes have been used in an attempt to resolve better the amplitude, decay, and location of the observed change in attenuation.…”

Section: Discussionmentioning

confidence: 99%

“…The 2003 San Simeon earthquake may have had an influence on the precursory signal observed by Chun et al . []. Although the distance between the two areas is quite large (65 km), the San Simeon earthquake has clearly been shown to have had a measurable effect on seismic velocity measurements in the Parkfield area [ Brenguier et al ., ].…”

Section: Discussionmentioning

confidence: 99%

“…However, temporal changes in seismic attenuation in Parkfield around the time of the 2004 M6.0 earthquake have been noted by Allmann and Shearer [] and Chun et al . []. Here, a systematic study of attenuation values immediately after the 2004 M6.0 earthquake is presented.…”

Section: Introductionmentioning

confidence: 99%

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Temporal changes in attenuation associated with the 2004 M6.0 Parkfield earthquake

et al. 2013

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Elevated seismic attenuation is often observed in fault zones due to the high degree of fracturing and fluid content. However, temporal changes in attenuation at the time of an earthquake are poorly constrained but can give indications of fracture damage and healing. In this study, spectral ratios between earthquakes within repeating clusters are calculated in an attempt to resolve temporal variations in attenuation at the time of the 2004 M6.0 Parkfield earthquake. A sharp increase in attenuation is observed immediately after the earthquake, which then decays over the next 2 years. Influences of intercluster magnitude variations, time window length and previously reported postseismic velocity changes are investigated. The postseismic decay is fit by a logarithmic function. The timescale of the decay is found to be similar to that in GPS data and ambient seismic noise velocities following the 2004 M6.0 Parkfield earthquake. The amplitude of the attenuation change corresponds to a decrease of approximately 10% in Qp at the time of the earthquake. The greatest changes are recorded on the northeast of the fault trace, consistent with preferential damage in the extensional quadrant behind a north‐westerly propagating rupture tip. Our analysis suggests that significant changes in seismic attenuation and hence fracture dilatancy during coseismic rupture are limited to depths of less than about 5 km.

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Section: Discussionmentioning

confidence: 67%

Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temporal changes in attenuation associated with the 2004 M6.0 Parkfield earthquake

et al. 2013

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Modern observations of the effect of earthquakes on the Chandler wobble

Smylie

Henderson²,

Zuberi

2015

Journal of Geodynamics

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Seismic Attenuation Monitoring of a Critically Stressed San Andreas Fault

Malagnini

Parsons

2020

Geophysical Research Letters

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We show that seismic attenuation (Q −1 S) along the San Andreas fault (SAF) at Parkfield correlates with the occurrence of moderate-to-large earthquakes at local and regional distances. Earthquake-related Q −1 S anomalies are likely caused by changes in permeability from dilatant static stress changes, damage by strong shaking from local sources, and pore unclogging/clogging from mobilization of colloids by dynamic strains. We find that, prior to the 2004 M6 Parkfield earthquake, prefailure conditions for some local events of moderate magnitude correspond to positive anomalies of Q −1 S on the Pacific side, with local and regional earthquakes producing sharp attenuation reversals. After the 2004 Parkfield earthquake, we see higher Q −1 S anomalies along the SAF, but low sensitivity to local and regional earthquakes, probably because the mainshock significantly altered the permeability state of the rocks adjacent to the SAF, and its sensitivity to earthquake-induced stress perturbations. Plain Language Summary We discovered that along the San Andreas fault, the damping of seismic energy through the Earth's crust is modulated by the state of stress in the crust, especially when the fault is close to rupture. The phenomenon depends on the density of cracks that permeate the rock, their interconnection, and the degree that they are filled with fluids. We show examples where attenuation, and thus permeability, is modulated by (i) damage from local earthquake shaking, (ii) dilatation imposed by local earthquakes, and (iii) clogging and unclogging of cracks induced by ground motion from distant earthquakes. These examples correlate with observed water well level changes. We note significant changes to the attenuation signal after the 2004 M6.0 Parkfield earthquake, with less sensitivity to local and distant earthquakes.

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Precursory Rise of P-Wave Attenuation before the 2004 Parkfield Earthquake

Cited by 8 publications

References 43 publications

Temporal changes in attenuation associated with the 2004 M6.0 Parkfield earthquake

Temporal changes in attenuation associated with the 2004 M6.0 Parkfield earthquake

Modern observations of the effect of earthquakes on the Chandler wobble

Seismic Attenuation Monitoring of a Critically Stressed San Andreas Fault

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