Hydrothermal system beneath Aso volcano as inferred from self-potential mapping and resistivity structure

Häse, H.; Hashimoto, Takeshi; Sakanaka, Shin’ya; Kanda, Wataru; Tanaka, Yoshikazu

doi:10.1016/j.jvolgeores.2004.12.005

Cited by 66 publications

(54 citation statements)

References 23 publications

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“…The DDS can act as preferential channels between the deep aquifer and the surface while in other parts of the volcanic edifice, the groundwater may consist solely of cold water flow. There are numerous examples of these hydrogeological systems such as on Usu and Aso volcanoes (Japan), Long Valley caldera and the Hawaiian Islands (USA) (Peterson, 1972;Sorey et al, 1991;Hase et al, 2005;Hase et al, 2010). As calderas are usually characterized by a topographic depression, it is common to find groundwater flow within the volcanic rocks as well as sizeable bodies of water on their surface (e.g., Farrar et al, 2003;Pribnow et al, 2003;Join et al, 2005;Pagli et al, 2006;Zlotnicki et al, 2009;Todesco et al, 2010).…”

Section: Groundwater Flow In Active Calderasmentioning

confidence: 99%

“…While rocks are poor thermal conductors and cannot efficiently transfer heat throughout the entire edifice, volcanic gas and superheated aqueous fluids are excellent thermal conductors, which will both draw the heat from the magma and control heat distribution within the volcanic edifice. Consequently, sustained gas, superheated aqueous fluids and heat flux within the ground could generate and support hydrothermal fluid circulation (Finizola et al, 2002;Chiodini et al, 2005;Bruno et al, 2007;Hase et al, 2010 and references therein). In the case of an open system such as at Masaya volcano, where the magma is directly in contact with the atmosphere, magmatic gases are easily evacuated through the open conduit and thus only a small percentage of the total gas flux may escape diffusely through the surrounding edifice.…”

Section: Introductionmentioning

confidence: 99%

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A geochemical and geophysical investigation of the hydrothermal complex of Masaya volcano, Nicaragua

Mauri

Williams‐Jones

Saracco

et al. 2012

Journal of Volcanology and Geothermal Research

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a b s t r a c t KeywordsMasaya Hydrothermal Self-potential Wavelet Groundwater Volcano Masaya volcano, Nicaragua, is a persistently active volcano characterized by continuous passive degassing for more than 150 years through the open vent of Santiago crater. This study applies self-potential, soil CO 2 and ground temperature measurements to highlight the existence of uprising fluids associated to diffuse degassing structures throughout the volcano. The diffuse degassing areas are organized in a semi-circular pattern and coincide with several visible and inferred surface volcanic structures (cones, fissure vents) and likely consist of a network of buried faults and dykes that respectively channel uprising flow and act as barrier to gravitational groundwater flow. Water depths have been estimated by multi-scale wavelet tomography of the self-potential data using wavelets from the Poisson kernel family. Compared to previous water flow models, our water depth estimates are shallower and mimic the topography, typically less than 150 m below the surface. Between 2006 and 2010, the depths of rising fluids along the survey profiles remained stable suggesting that hydrothermal activity is in a steady state. This stable activity correlates well with the consistency of the volcanic activity expressed at the surface by the continuously passive degassing. When compared to previous structural models of the caldera floor, it appears that the diffuse degassing structures have an important effect on the path that shallow groundwater follows to reach the Laguna de Masaya in the eastern part of the caldera. The hydrogeological system is therefore more complex than previously published models and our new structural model implies that the flow of shallow groundwater must bypass the intrusions to reach the Laguna de Masaya. Furthermore, these diffuse degassing structures show clear evidence of activity and must be connected to a shallow magmatic or hydrothermal reservoir beneath the caldera. As such, the heat budget for Masaya must be significantly larger than previously estimated.

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Section: Groundwater Flow In Active Calderasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A geochemical and geophysical investigation of the hydrothermal complex of Masaya volcano, Nicaragua

Mauri

Williams‐Jones

Saracco

et al. 2012

Journal of Volcanology and Geothermal Research

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“…In particular, we have already used the MT method to evaluate the large-scale subsurface resistivity structure present within the seismogenic zone beneath the Japanese Archipelago Island Arc system (Ogawa et al, 2001;Uyeshima et al, 2005;Yoshimura et al, 2009), and to evaluate the smaller-scale (shallow) resistivity structure beneath a number of historically active Japanese volcanoes (Ogawa et al, 1998;Hase et al, 2005;Aizawa et al, 2009b;Kanda et al, 2010).…”

Section: Magnetotelluric Monitoringmentioning

confidence: 99%

Magnetotelluric and temperature monitoring after the 2011 sub-Plinian eruptions of Shinmoe-dake volcano

et al. 2013

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Three sub-Plinian eruptions took place on 26-27 January 2011 at Shinmoe-dake volcano in the Kirishima volcanic group, Japan. During this event, GPS and tiltmeters detected syn-eruptive ground subsidence approximately 7 km to the WNW of the volcano. Starting in March 2011, we conducted broad-band magnetotelluric (MT) measurements at a site located 5 km NNW of the volcano, beneath which the Shinmoe-dake magma plumbing system may exist. In addition, temperature monitoring of fumaroles and hot-springs near the MT site was initiated in July 2011. Our MT data record changes in apparent resistivity of approximately ±5%, along with a ±1• phase change in the off-diagonal component of the impedance tensor (Z xy and Z yx ). Using 1-D inversion, we infer that these slight changes in resistivity took place at relatively shallow depths of only a few hundred meters, at the transition between a near-surface resistive layer and an underlying conductive layer. Resistivity changes observed since March 2012 are correlated with the observed temperature increases around the MT monitoring site. These observations suggest the existence beneath the MT site of pathways which enable volatile escape.

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“…Electrical lows located at the periphery of the volcano are interpreted to be related to saturated meteoric water downflow. Within the active cone, the shallow magma reservoir progressively heats the meteoric water, giving rise to convective hydrothermal upwellings, which induce SP peaks (Zablocki, 1976;Finizola et al, 2002;Hase et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Electric potential anomaly induced by humid air convection within Piton de La Fournaise volcano, La Réunion Island

et al. 2017

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a b s t r a c tSelf potential (SP) anomalies over Piton de La Fournaise volcano (La Réunion Island) are generally inter-preted as resulting from meteoritic water porous flow. However, there is no clear evidence that the subsurface is permanently saturated. Recently, a convective subsurface airflow has been evidenced within a quiescent cone at Piton de La Fournaise (Formica Leo). SP and thermal anomalies are reported on the unsaturated edifice and are seen to be correlated. It is proposed that the SP signal is generated by the movement of water films present on the porous matrix, induced by the intense humid airflow within Formica Leo. The structure of the cone, determined from electrical resistivity tomography (ERT), ground penetrating radar (GPR), microgravimetric and kinematic GPS data, is used to constrain a 3D numerical model of the air convection. The calculated temperature is then used to derive the related SP signal, the electrokinetic coupling coefficient being estimated from direct observations of the electrical resistivity of the soil. Extrapolating these results to the scale of the volcano, it is thus proposed that a cold humid air-flow enters the flanks of the 400 m-high terminal dome, flows up along the sloped and stratified volcanic layers before exiting through the vertical fractures around the Dolomieu collapse. It is demonstrated that the SP anomalies catches the main features recovered over the entire volcano. This result strongly sug-gests that humid airflow may play a major role on the generation of SP anomalies at Piton de la Fournaise volcano, and perhaps in other unsaturated volcanic edifices.

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Hydrothermal system beneath Aso volcano as inferred from self-potential mapping and resistivity structure

Cited by 66 publications

References 23 publications

A geochemical and geophysical investigation of the hydrothermal complex of Masaya volcano, Nicaragua

A geochemical and geophysical investigation of the hydrothermal complex of Masaya volcano, Nicaragua

Magnetotelluric and temperature monitoring after the 2011 sub-Plinian eruptions of Shinmoe-dake volcano

Electric potential anomaly induced by humid air convection within Piton de La Fournaise volcano, La Réunion Island

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