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

Kelly, C. M.; Rietbrock, Andreas; Faulkner, Daniel R.; Nadeau, R. M.

doi:10.1002/jgrb.50088

Cited by 33 publications

(45 citation statements)

References 72 publications

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“…It is well known that permeability increases in fault zones after seismic events, when preferential flow paths are enhanced or newly created [Cox et al, 2014;Kitagawa et al, 2007;Wang and Manga, 2010]. Within a few years or decades, permeability progressively returns to the preseismic conditions due to mineralization of the fractures [Brenguier et al, 2008;Kelly et al, 2013]. The available data set is rich for all PGA classes down to at least 1000 m depth ( Figure S8).…”

Section: Geological Provinces and Seismotectonic Activity As Main Facmentioning

confidence: 99%

A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

2017

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A comprehensive worldwide permeability data set has been compiled consisting of 29,000 in situ permeabilities from 221 publications and reports and delineating the permeability distribution in crystalline rocks into depths of 2000 meters below ground surface (mbgs). We analyze the influence of technical factors (measurement method, scale effects, preferential sampling, and hydraulic anisotropy) and geological factors (lithology, current stress regime, current seismotectonic activity, and long‐term tectonogeological history) on the permeability distribution with depth, by using regression analysis and k‐means clustering. The influence of preferential sampling and hydraulic anisotropy are negligible. A scale dependency is observed based on calculated rock test volumes equaling 0.6 orders of magnitude of permeability change per order of magnitude of rock volume tested. Based on the entire data set, permeability decreases as log(k) = −1.5 × log(z) − 16.3 with permeability k (m2) and positively increasing depth z (km), and depth is the main factor driving the permeability distribution. The permeability variance is about 2 orders of magnitude at all depths, presumably representing permeability variations around brittle fault zones. Permeability and specific yield/storage exhibit similar depth trends. While in the upper 200 mbgs fracture flow varies between confined and unconfined, we observe confined fracture and matrix flow below about 600 mbgs depth. The most important geological factors are current seismotectonic activity (determined by peak ground acceleration) and long‐term tectonogeological history (determined by geological province). The impact of lithology is less important. Based on the regression coefficients derived for all the geological key factors, permeability ranges of crystalline rocks at site scale can be predicted. First tests with independent data sets are promising.

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Section: Geological Provinces and Seismotectonic Activity As Main Facmentioning

confidence: 99%

A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

2017

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“…Following the 2004 M 6 Parkfield earthquake, the recurrence times of these clusters significantly decreased, and then gradually increased, but with minimal change in moment [ Chen et al, ]. Allmann and Shearer [] and Kelly et al [] found both attenuation and earthquake stress drop to change along the fault following the M 6 earthquake. My aims are twofold.…”

Section: Introductionmentioning

confidence: 99%

Stress drops of repeating earthquakes on the San Andreas Fault at Parkfield

Abercrombie

2014

Geophysical Research Letters

106

203

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I calculate well-resolved corner frequencies and stress drops for 25 earthquakes (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006) in the three repeating sequences targeted by the San Andreas Fault Observatory at Depth, using borehole data and multiple, highly correlated empirical Green's functions (EGFs). The earthquakes in the largest magnitude (M~2.1) cluster exhibit source spectra well-fit by a circular source model. The corner frequencies correlate with those from the regional study by Allmann and Shearer (2007), suggesting that the interevent variability is resolvable. The earthquakes have stress drops between 25 and 65 MPa, with a gradual increase before the 2004 M6 earthquake, followed by an immediate decrease, then a rapid return to previous levels. The spectra of the cluster of M~1.9 earthquakes include high-frequency energy not fit by simple source models and so stress drops are unreliable, and probably underestimated (1-20 MPa). There is no correlation with previous studies, and interevent variation is not resolvable. The earthquakes in the smallest magnitude cluster (M~1.8) have the highest corner frequencies, but similar stress drops (4-120 MPa). The stress drops exhibit the same temporal variation as the first cluster, but there is poor correlation with Allmann and Shearer (2007), probably because their frequency bandwidth is too limited.

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“…For completeness, we also use the P‐wave arrival, either the rotated component or a stack of all three components, as performed by Kelly et al . (). First, we use every event as a reference.…”

Section: Changes In Anisotropic Attenuation With Timementioning

confidence: 97%

“…Kelly et al . () observed temporal variations in P‐wave attenuation before and after the 2004 M6.0 Parkfield earthquake. They attributed this variation to fracture dilatancy due to changes in stress conditions and fluid pressure before and after the earthquake.…”

Section: Introductionmentioning

confidence: 99%

Measuring changes in fracture properties from temporal variations in anisotropic attenuation of microseismic waveforms

Usher

Kendall

Kelly

et al. 2017

Geophysical Prospecting

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We investigate fracture‐induced attenuation anisotropy in a cluster of events from a microseismic dataset acquired during hydraulic fracture stimulation. The dataset contains 888 events of magnitude −3.0 to 0.0. We use a log‐spectral‐amplitude‐ratio method to estimate change in t∗ over a half‐hour time period where fluid is being injected and an increase in fracturing from S‐wave splitting analysis has been previously inferred. A Pearson's correlation analysis is used to assess whether or not changes in attenuation with time are statistically significant. P‐waves show no systematic change in t∗ during this time. In contrast, S‐waves polarised perpendicular to the fractures show a clear and statistically significant increase with time, whereas S‐waves polarised parallel to the fractures show a weak negative trend. We also compare t∗ between the two S‐waves, finding an increase in Δt∗ with time. A poroelastic rock physics model of fracture‐induced attenuation anisotropy is used to interpret the results. This model suggests that the observed changes in t* are related to an increase in fracture density of up to 0.04. This is much higher than previous estimates of 0.025 ± 0.002 based on S‐wave velocity anisotropy, but there is considerably more scatter in the attenuation measurements. This could be due to the added sensitivity of attenuation measurement to non‐aligned fractures, fracture shape, and fluid properties. Nevertheless, this pilot study shows that attenuation measurements are sensitive to fracture properties such as fracture density and aspect ratio.

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

Cited by 33 publications

References 72 publications

A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

Stress drops of repeating earthquakes on the San Andreas Fault at Parkfield

Measuring changes in fracture properties from temporal variations in anisotropic attenuation of microseismic waveforms

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