Magnetotelluric imaging of upper‐crustal convection plumes beneath the Taupo Volcanic Zone, New Zealand

Bertrand, E. A.; Caldwell, T. G.; Hill, G. J.; Wallin, Erin L.; Bennie, S. L.; Cozens, N.; Onacha, S.; Ryan, G.; Walter, Christina; Zaino, A.; Wameyo, Peter

doi:10.1029/2011gl050177

Cited by 98 publications

(65 citation statements)

References 34 publications

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“…Finally, failure of the sealed surface of the vertical conduit led to the 2014 phreatic eruption. The sealed surface may be produced by the precipitation of altered clay minerals or hydrothermal secondary deposits near the surface (e.g., Bertrand et al 2012;Maeda et al 2015). …”

Section: Discussionmentioning

confidence: 99%

Preparatory and precursory processes leading up to the 2014 phreatic eruption of Mount Ontake, Japan

et al. 2015

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We analyzed seismicity linked to the 2014 phreatic eruption of Mount Ontake, Japan, on 27 September 2014. We first relocated shallow volcano tectonic (VT) earthquakes and long-period (LP) events from August to September 2014. By applying a matched-filter technique to continuous waveforms using these relocated earthquakes, we detected numerous additional micro-earthquakes beneath the craters. The relocated VT earthquakes aligned on a near-vertical plane oriented NNW-SSE, suggesting they occurred around a conduit related to the intrusion of magmatic-hydrothermal fluids into the craters. The frequency of VT earthquakes gradually increased from 6 September 2014 and reached a peak on 11 September 2014. After the peak, seismicity levels remained elevated until the eruption. b-values gradually increased from 1.2 to 1.7 from 11 to 16 September 2014 then declined gradually and dropped to 0.8 just before the eruption. During the 10-min period immediately preceding the phreatic eruption, VT earthquakes migrated in the up-dip direction as well as laterally along the NNW-SSE feature. The migrating seismicity coincided with an accelerated increase of pre-eruptive tremor amplitude and with an anomalous tiltmeter signal that indicated summit upheaval. Therefore, the migrating seismicity suggests that the vertical conduit was filled with pressurized fluids, which rapidly propagated to the surface during the final 10 min before the eruption.

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Section: Discussionmentioning

confidence: 99%

Preparatory and precursory processes leading up to the 2014 phreatic eruption of Mount Ontake, Japan

et al. 2015

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“…All of these can be indicative of modern or past geothermal fluid circulation (Newman et al, 2008;Spichak and Manzella, 2009;Wannamaker et al, 2007Wannamaker et al, , 2006. Magnetotelluric methods in particular are commonly used at the geothermal field-scale in order to identify conductive zones and locate and characterize geothermal fluid flow conduits and conductive clay caps (e.g., Bertrand et al, 2012;Cumming and Mackie, 2007;Uchida and Sasaki, 2006;Wannamaker et al, 2013aWannamaker et al, , 2011Wannamaker et al, , 2008Wannamaker et al, , 2007Wannamaker et al, , 2006. At the crustal-and lithospheric-scale, conductivity anomalies identified by magnetotelluric methods indicate both active and ancient tectonic and magmatic features as a result of modern or past fluid circulation within these structures (e.g., Meqbel et al, 2014).…”

Section: Crustal Conductivity Datamentioning

confidence: 99%

Regional crustal-scale structures as conduits for deep geothermal upflow

Siler

Kennedy

2016

Geothermics

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a b s t r a c tGeothermal fluids produced from two of the largest production geothermal fields in the Great Basin have helium isotope ratios that are anomalously high relative to basin-wide trends. These data indicate that the geothermal systems, Dixie Valley, Nevada and McGinness Hills, Nevada have an anomalously high fraction of mantle derived fluid. These connections to deeply derived fluid and heat may supplement crustal heat production and be responsible, in part, for the anomalously high production capacity, relative to other Great Basin geothermal fields, that Dixie Valley and McGinness Hills support. Deep-seated crustal structures across the Great Basin and around the world are known to be associated with structural reactivation, can have relatively high permeability, and can act as fluid flow conduits. These deep seated structures across the Great Basin control upflow of deeply derived heat and fluids into the shallow geothermal systems at Dixie Valley and McGinness Hills, contributing to their productivity.

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“…The method is closely related to the groundbased magnetotelluric (MT) method, which also uses natural EM signals and has been applied to a wide variety of targets from near-surface to deeper mantle studies (Bastani et al, 2009;Bertrand et al, 2012;Rippe et al, 2013). MT measurements require contact with the ground and are thus relatively slow and expensive if large areas are to be explored.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional imaging of a Ag-Au-rich epithermal system in British Columbia, Canada, using airborne z-axis tipper electromagnetic and ground-based magnetotelluric data

et al. 2016

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We have evaluated results from a study combining airborne z-axis tipper electromagnetic (ZTEM) and ground-based magnetotelluric (MT) data to image an epithermal system in British Columbia. The spatially coincident use of these two methods allowed for a direct comparison of both data sets in the overlapping frequency band and showed that both measurements were consistent. Inversion of just the ZTEM data suffered from the lack of electric field amplitude information, which could be provided by the MT data. Three-dimensional inversion modeling of the two individual data sets was performed. Models of electrical resistivity derived from both data sets were consistent and could be correlated with the geological and structural setting of the mineralization. Gold is associated with disseminated pyrite and marcasite in quartz-sericite-altered felsic volcanic rocks and intrusions, especially near the contact with mafic volcanic rocks and a late diorite intrusion. The quartz-sericite alteration yields a conductivity anomaly, relative to the more resistive mafic country rocks. Although ZTEM and MT do not possess the resolution of the geologic model derived from borehole data, our model agrees well with a regional assessment of the deposit.

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Magnetotelluric imaging of upper‐crustal convection plumes beneath the Taupo Volcanic Zone, New Zealand

Cited by 98 publications

References 34 publications

Preparatory and precursory processes leading up to the 2014 phreatic eruption of Mount Ontake, Japan

Preparatory and precursory processes leading up to the 2014 phreatic eruption of Mount Ontake, Japan

Regional crustal-scale structures as conduits for deep geothermal upflow

Three-dimensional imaging of a Ag-Au-rich epithermal system in British Columbia, Canada, using airborne z-axis tipper electromagnetic and ground-based magnetotelluric data

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