Long‐term monitoring of ULF electromagnetic fields at Parkfield, California

Kappler, K. N.; Morrison, H. F.; Egbert, G. D.

doi:10.1029/2009jb006421

Cited by 27 publications

(18 citation statements)

References 29 publications

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“…Kappler et al 2010). These installations attempted to monitor long-term electric (and magnetic) field variations of internal origin due to resistivity variations assiciated with earthquakes, large scale fluid flow or other causes.…”

Section: *Abstractmentioning

confidence: 99%

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Becken

Ritter

2011

Surv Geophys

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Fluids residing in interconnected porosity networks have a significant weakening effect on rheology of rocks and can strongly influence deformation along fault zones. The magnetotelluric (MT) technqiue is sensitive to interconnected fluid networks, and can image these zones on crustal and upper mantle scales. MT has imaged several prominent electrically conductive anomalies at the San Andreas fault which have been attributed to the presence of saline fluids within such networks, and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle portion of the crust, and where these fluids are kept at high pressures, fault creep is supported. In response to fluid flux from deeper levels in combination with meteoric and crustal metamorphic fluid supply, and in response to fault creep, high-conductivity zones develop as fault zone conductors in the brittle portion of crust. In turn, the absence of crustal fluid pathays may be characteristic for mechanically locked segments. MT models suggest that those fluids are trapped at depth and kept at high pressures. It is speculated that fluids may infiltrate neighbouring rocks and induce non-volcanic tremor. MT has imaged several prominent electrically conductive anomalies at the San Andreas fault which have been attributed to the presence of saline fluids within such networks, and which have been associated with tectonic processes. These models suggest that ongoing fluid release in the upper mantle and lower crust is closely related to the mechanical state of the crust. Where fluids are drained into the brittle portion of the crust, and where these fluids are kept at high pressures, strain provides a means to develop and maintain permeability structure, and thus electrical conductivity, within the damage zone. Accordingly, these conductivity models played an important role in pin-pointing the SAFOD drilling location near Parkfield. *abstractClick here to download abstract: abstract.txt Surv. Geophys. manuscript No.In this paper, we consider MT studies at the SAF near Hollister and Carrizo The SAF has also been a target for telluric (Madden et al. 1993;Park et al. 2007) and magnetotelluric monitoring (e.g. Kappler et al. 2010). These installations attempted to monitor long-term electric (and magnetic) field variations of internal origin due to resistivity variations assiciated with earthquakes, large scale fluid flow or other causes. To date, it was not possible to identify significant field variations which can be attributed to tectonic processes. In this paper, we don't discuss details of this issue. 7The main objective of this paper is to review the MT results from the SAF in combination with other geophysical, geological and geochemical data and models in order to address fluid-related processes and their potential implications on the geodynamic setting, active tectonic processes and the mechanical ...

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Section: *Abstractmentioning

confidence: 99%

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Becken

Ritter

2011

Surv Geophys

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“…Occasionally, an observation is made prominent in the scientific community or perhaps in the public News Media, FraserSmith et al (1990) being a notable example. But rebuttals and vigorous debate also remain, Karakelian et al (2002), Kappler et al (2010), and Thomas et al (2010) being notable recent examples.…”

Section: Introductionmentioning

confidence: 99%

The Pulse Azimuth effect as seen in induction coil magnetometers located in California and Peru 2007–2010, and its possible association with earthquakes

Dunson

Bleier

Roth

et al. 2011

Nat. Hazards Earth Syst. Sci.

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Abstract. The QuakeFinder network of magnetometers has recorded geomagnetic field activity in California since 2000. Established as an effort to follow up observations of ULF activity reported from before and after the M = 7.1 Loma Prieta earthquake in 1989 by Stanford University, the QuakeFinder network has over 50 sites, fifteen of which are high-resolution QF1005 and QF1007 systems. Pairs of highresolution sites have also been installed in Peru and Taiwan.Increases in pulse activity preceding nearby seismic events are followed by decreases in activity afterwards in the three cases that are discussed here. In addition, longer term data is shown, revealing a rich signal structure not previously known in QuakeFinder data, or by many other authors who have reported on pre-seismic ULF phenomena. These pulses occur as separate ensembles, with demonstrable repeatability and uniqueness across a number of properties such as waveform, angle of arrival, amplitude, and duration. Yet they appear to arrive with exponentially distributed inter-arrival times, which indicates a Poisson process rather than a periodic, i.e., stationary process.These pulses were observed using three-axis induction coil magnetometers that are buried 1-2 m under the surface of the Earth. Our sites use a Nyquist frequency of 16 Hertz (25 Hertz for the new QF1007 units), and they record these pulses at amplitudes from 0.1 to 20 nano-Tesla with durations of 0.1 to 12 s. They are predominantly unipolar pulses, which may imply charge migration, and they are stronger in the two horizontal (north-south and east-west) channels than they are in the vertical channels. Pulses have been seen to occur in bursts lasting many hours. The pulses have large Correspondence to: J. C. Dunson (cdunson@quakefinder.com) amplitudes and study of the three-axis data shows that the amplitude ratios of the pulses taken from pairs of orthogonal coils is stable across the bursts, suggesting a similar source. This paper presents three instances of increases in pulse activity in the 30 days prior to an earthquake, which are each followed by steep declines after the event. The pulses are shown, methods of detecting the pulses and calculating their azimuths is developed and discussed, and then the paper is closed with a brief look at future work.

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“…Kappler et al (2010) (Kim and Cho, 2011). Kim et al (2009) have made successful interpretation of TL electrical-resistivity data sets by developing a 4D inversion scheme, which simultaneously inverts multiple TL data sets with regularizations in both space and time domains effectively to reduce inversion artifacts.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

4D inversion of time-lapse magnetotelluric data sets for monitoring geothermal reservoir

Nam

Song

Jang

et al. 2017

Journal of Applied Geophysics

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Long‐term monitoring of ULF electromagnetic fields at Parkfield, California

Cited by 27 publications

References 29 publications

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

Magnetotelluric Studies at the San Andreas Fault Zone: Implications for the Role of Fluids

The Pulse Azimuth effect as seen in induction coil magnetometers located in California and Peru 2007–2010, and its possible association with earthquakes

4D inversion of time-lapse magnetotelluric data sets for monitoring geothermal reservoir

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