A large hydrothermal reservoir beneath Taal Volcano (Philippines) revealed by magnetotelluric resistivity survey: 2D resistivity modeling

Yamaya, Yusuke; Alanis, Paul Karson; Takeuchi, Akihiro; Cordon, Juan M.; Mogi, Toru; Hashimoto, Takeshi; Sasai, Yoichi; Nagao, Toshiyasu

doi:10.1007/s00445-013-0729-y

Cited by 37 publications

(41 citation statements)

References 36 publications

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“…Such a bell-shaped conductor beneath the central cone or geothermal/fumarolic area has been previously detected at other volcanoes (e.g. Nurhasan et al 2006;Kanda et al 2008;Komori et al 2013;Yamaya et al 2013;Usui et al 2017). With reference to the conceptual model of a geothermal system described by Pellerin et al (1996), we interpret that the bell-shaped conductor and the resistive body represent an impermeable layer consisting of altered clays and a bounded hydrothermal reservoir, respectively.…”

Section: Discussionmentioning

confidence: 99%

“…Since resistivity is sensitive to temperature (including thermal alteration) and the presence of fluids, it is commonly applied to infer the structural setting in volcanic and geothermal environments (e.g. Nurhasan et al 2006;Kanda et al 2008;Komori et al 2013;Yamaya et al 2013;Gasperikova et al 2015;Seki et al 2015Seki et al , 2016Usui et al 2017). In our study area, we obtained magnetotelluric (MT) data in the dense site array (Ogawa et al 2011;Yoshimura et al 2012Yoshimura et al , 2013 to infer the structure of Hakone volcano, with a focus on shallow caldera Fig.…”

Section: Introductionmentioning

confidence: 99%

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Resistivity characterisation of Hakone volcano, Central Japan, by three-dimensional magnetotelluric inversion

Yoshimura

Ogawa

Yukutake

et al. 2018

Earth Planets Space

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On 29 June 2015, a small phreatic eruption occurred at Hakone volcano, Central Japan, forming several vents in the Owakudani geothermal area on the northern slope of the central cones. Intense earthquake swarm activity and geodetic signals corresponding to the 2015 eruption were also observed within the Hakone caldera. To complement these observations and to characterise the shallow resistivity structure of Hakone caldera, we carried out a threedimensional inversion of magnetotelluric measurement data acquired at 64 sites across the region. We utilised an unstructured tetrahedral mesh for the inversion code of the edge-based finite element method to account for the steep topography of the region during the inversion process. The main features of the best-fit three-dimensional model are a bell-shaped conductor, the bottom of which shows good agreement with the upper limit of seismicity, beneath the central cones and the Owakudani geothermal area, and several buried bowl-shaped conductive zones beneath the Gora and Kojiri areas. We infer that the main bell-shaped conductor represents a hydrothermally altered zone that acts as a cap or seal to resist the upwelling of volcanic fluids. Enhanced volcanic activity may cause volcanic fluids to pass through the resistive body surrounded by the altered zone and thus promote brittle failure within the resistive body. The overlapping locations of the bowl-shaped conductors, the buried caldera structures and the presence of sodium-chloride-rich hot springs indicate that the conductors represent porous media saturated by highsalinity hot spring waters. The linear clusters of earthquake swarms beneath the Kojiri area may indicate several weak zones that formed due to these structural contrasts.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Resistivity characterisation of Hakone volcano, Central Japan, by three-dimensional magnetotelluric inversion

Yoshimura

Ogawa

Yukutake

et al. 2018

Earth Planets Space

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“…MT survey is a useful geophysical approach for analyzing hydrothermal systems because hydrothermally altered minerals and hydrothermal fluids generally exhibit low resistivity, whereas igneous rocks are typically highly resistive (e.g., Simpson and Bahr, 2005). MT methods have been used to investigate the hydrothermal systems associated with many volcanoes (e.g., Nurhasan et al, 2006;Kanda et al, 2008;Yamaya et al, 2013). Such systems commonly consist of a highly conductive layer underlain by a relatively resistive zone in the shallow volcanic edifice.…”

Section: Introductionmentioning

confidence: 99%

Resistivity structure and geochemistry of the Jigokudani Valley hydrothermal system, Mt. Tateyama, Japan

Seki

Kanda

Tanbo

et al. 2016

Journal of Volcanology and Geothermal Research

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“…The fact that gases are not as conductive as fluids or clays means that these low permeable clayey caps are often underlain by slightly resistive regions. A number of volcanoes that have multiple recorded phreatic eruptions have been investigated by magnetotelluric surveys, including Kusatsu-Shirane volcano in Japan (Nurhasan et al 2006) and Taal volcano in the Philippines (Yamaya et al 2013). A significant number of these volcanoes are associated with near-surface conductive anomalies that have been interpreted to be low permeable clayey layers.…”

Section: Introductionmentioning

confidence: 99%

Imaging the hydrothermal system beneath the Jigokudani valley, Tateyama volcano, Japan: implications for structures controlling repeated phreatic eruptions from an audio-frequency magnetotelluric survey

et al. 2015

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This study focuses on the results of an audio-frequency magnetotelluric (AMT) survey across the Jigokudani valley, Tateyama volcano, Japan, to investigate the spatial relationship between the distribution of electrical resistivity and geothermal activity and to elucidate the geologic controls on both its phreatic eruption history and recent increase in phreatic activity. The AMT data were collected at eight locations across the Jigokudani valley in September 2013, with high quality data obtained from most sites, enabling the identification of an underground 2D resistivity structure from the transverse magnetic (TM) mode data. The data obtained during this study provided evidence of a large conductive region beneath the surface of the Jigokudani valley that is underlain by a resistive layer at depths below 500 m. The resistive layer is cut by a relatively conductive region that extends subvertically toward the shallow conductor. The shallow conductive region is divided into an uppermost slightly conductive section that is thought to be a lacustrine sediment layer of an extinct crater lake containing hydrothermal fluids and a lower section containing a mix of volcanic gases and hydrothermal fluids. The low permeability of the clay zone means that the uppermost clayey sediments allow the accumulation of gases in the lower section of the conductive region, suggesting the existence of a cap structure. The deep resistive layer likely consists of units similar to the granitic rocks that are widely exposed throughout the Jigokudani valley. We suggest that the relatively conductive zone that separates these granitic rocks represents a high-temperature volcanic gas conduit, given that the most active fumarole in the Jigokudani valley lies directly along the trajectory of this path.

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A large hydrothermal reservoir beneath Taal Volcano (Philippines) revealed by magnetotelluric resistivity survey: 2D resistivity modeling

Cited by 37 publications

References 36 publications

Resistivity characterisation of Hakone volcano, Central Japan, by three-dimensional magnetotelluric inversion

Resistivity characterisation of Hakone volcano, Central Japan, by three-dimensional magnetotelluric inversion

Resistivity structure and geochemistry of the Jigokudani Valley hydrothermal system, Mt. Tateyama, Japan

Imaging the hydrothermal system beneath the Jigokudani valley, Tateyama volcano, Japan: implications for structures controlling repeated phreatic eruptions from an audio-frequency magnetotelluric survey

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