An audio-magnetotelluric investigation in Terceira Island (Azores)

Santos, Fernando A. Monteiro; Trota, António; Soares, António O.; Luzio, Rafael; Lourenço, N.; Matos, Liliana; Almeida, Eugénio P.; Gaspar, J. L.; Miranda, Jorge Miguel

doi:10.1016/j.jappgeo.2005.12.001

Cited by 25 publications

(4 citation statements)

References 29 publications

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“…Although 3‐D codes for modelling and inversion of MT data are now available, the difficulties in deriving realistic models of complex geological structures have meant that most previous studies of volcanic areas (e.g. Matsushima et al 2001; Nurhasan et al 2006; Monteiro Santos et al 2006) have utilized 2‐D models to infer the main features of the resistivity structure. Only Muller & Haak (2004), using a 3‐D forward code based on Mackie & Madden (1993) and Mackie et al (1994), have presented a true 3‐D model of deep electrical conductivity structure beneath a volcano.…”

Section: Modelling Of Conductivity Structurementioning

confidence: 99%

“…Examples include not only a large number of Japanese studies (e.g. Mogi & Nakamura 1993; Ogawa et al 1998; Fuji‐ta et al 1999; Kagiyama et al 1999; Matsushima et al 2001; Asaue et al 2006; Nurhasan et al 2006) but also investigations in North America (Park & Torres‐Verdin 1988; Hill et al 2009), South America (Schilling et al 1997), Indonesia (Muller & Haak 2004), Europe (Manzella et al 2004; Monteiro Santos et al 2006) and the Pacific (Ingham 1992). In this paper, we report the results of an MT study of the structure of Mt Ruapehu and its surrounding area aimed at identifying possible accumulations of magma beneath the volcano, the nature of passages by which magma moves from depth to the surface, and if possible, the link between Ruapehu and the other volcanoes of the Tongariro complex.…”

Section: Introductionmentioning

confidence: 99%

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A magnetotelluric study of Mount Ruapehu volcano, New Zealand

Ingham¹,

Bibby²,

Heise³

et al. 2009

Geophysical Journal International

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S U M M A R YMt Ruapehu is an active andesite cone volcano, which marks the southern termination of the Kermadec volcanic arc. Results from 40 broad-band magnetotelluric soundings have been analysed using the phase tensor. This approach provides a way of determining dimensionality, allowing for distortion removal, and visualizing data in a 3-D situation. The phase tensor analysis suggests that the shallow resistivity structure is largely 1-D in character, but that the deeper structure requires a 3-D interpretation. 1-D inversions show that at sites on Ruapehu a shallow conductive layer lies between a high resistivity layer, of a few hundred metres thickness, and higher resistivity layer corresponding to basement greywacke. The low resistivity layer is contiguous with the waters of the highly acidic Crater Lake, and thus is believed to be the hydraulically controlled upper limit of a zone of acid alteration overlain by dry volcanic rock and ash. To the southwest of the volcano the conductive layer merges with a surface conductor associated with Tertiary sediments. Following initial 2-D inversions, the deep resistivity structure has been derived through 3-D inversion of data from 38 sites. This indicates the existence of a dyke-like low resistivity zone that persists to at least 10 km depth and extends from beneath the summit of Ruapehu to the northeast where it appears to connect to a poorly constrained region of high conductivity, which lies outside the network of measurement sites. The low resistivity dyke-like feature may be identified with a volcanic feeder system, which also supplies the other volcanoes of the Tongariro Volcanic Centre and marks the conduit by which hot gases and (occasionally) magma reach the surface.

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Section: Modelling Of Conductivity Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A magnetotelluric study of Mount Ruapehu volcano, New Zealand

Ingham¹,

Bibby²,

Heise³

et al. 2009

Geophysical Journal International

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“…Using the same dataset, 2D inversion with the rEbOcc code (siripunvaraporn & Egbert 2000) confirmed the validity of the 1D approach. recently, 3D results indicated that the ocean effects start above 4 s for the phase and 20 s for the apparent resistivity (Pous et al 2002;Monteiro santos et al 2006). therefore these effects can be neglected for the investigated period range.…”

Section: Resultsmentioning

confidence: 94%

Structural pattern of the western Las Cañadas caldera (Tenerife, Canary Islands) revealed by audiomagnetotellurics

et al. 2008

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the local and regional structural pattern of volcanic edifices strongly controls the space distribution of electrical resistivity. Here we report on the structural context of the western part of the Las cañadas caldera of tenerife (Lcc) thought to have initiated the formation of the caldera. Using a new dataset of 11 audiomagnetotelluric tensors we emphasize the resistivity distribution of Ucanca caldera and propose a major revision of its extension. We find that Ucanca caldera has a limited westwards extent and that El cedro sector is a depression margin of the caldera. According to the extent of hydrothermalized rocks at the base of the Lcc wall and the distribution of Pico teide -Pico Viejo vents, we constrain the location and size of Ucanca caldera. the interpretation of these results also constrains the extension of the Icod Valley and proposes a headwall located below the Pico teide -Pico Viejo complex.

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“…Field data acquisition and indoor data processing have been underway. AMT survey has already displayed its unusual advantages in prospecting for metal ore, terrestrial heat and geological structures (Schnegg et al 1983, Clerc et al 1984, Bronner and Fourno 1992, Ogawa et al 1994, Balyavskii and Sukhoi 2004, Santos et al 2006, 2007Strangway et al 1973, Yamaguchi et al 2010, Abdelzaher et al 2011. However, because research on the gas hydrate in the permafrost region in our country has been at its very early stage, the AMT method is rarely used to prospect for gas hydrates and few related reports come into sight.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Response Characteristics of Audio-magnetotelluric for Gas Hydrate in the Qilian Mountain Permafrost, China

Xiao

Zou

et al. 2015

Acta Geophys.

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A b s t r a c t Audio-magnetotelluric (AMT) method is a kind of frequencydomain sounding technique, which can be applied to gas hydrate prospecting and assessments in the permafrost region due to its high frequency band. Based on the geological conditions of gas hydrate reservoir in the Qilian Mountain permafrost, by establishing high-resistance abnormal model for gas hydrate and carrying out numerical simulation using finite element method (FEM) and nonlinear conjugate gradient (NLCG) method, this paper analyzed the application range of AMT method and the best acquisition parameters setting scheme. When porosity of gas hydrate reservoir is less than 5%, gas hydrate saturation is greater than 70%, occurrence scale is less than 50 m, or bury depth is greater than 500 m, AMT technique cannot identify and delineate the favorable gas hydrate reservoir. Survey line should be more than twice the length of probable occurrence scale, while tripling the length will make the best result. The number of stations should be no less than 6, and 11 Unauthenticated Download Date | 4/24/17 5:15 AM RESPONSE CHARACTERISTICS OF AUDIO-MAGNETOTELLURIC 1369stations are optimal. At the high frequency section (10~1000 Hz), there should be no less than 3 frequency points, 4 being the best number.

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An audio-magnetotelluric investigation in Terceira Island (Azores)

Cited by 25 publications

References 29 publications

A magnetotelluric study of Mount Ruapehu volcano, New Zealand

A magnetotelluric study of Mount Ruapehu volcano, New Zealand

Structural pattern of the western Las Cañadas caldera (Tenerife, Canary Islands) revealed by audiomagnetotellurics

Numerical Simulation of Response Characteristics of Audio-magnetotelluric for Gas Hydrate in the Qilian Mountain Permafrost, China

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