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| Titel |
Diffuse CO₂ and ²²²Rn degassing monitoring of Ontake volcano, Japan} |
| VerfasserIn |
Mar Alonso, Takeshi Sagiya, Ángela Meneses-Gutiérrez, Eleazar Padrón, Pedro A. Hernández, Nemesio M. Pérez, Gladys Melián, Germán D. Padilla |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250146416
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| Publikation (Nr.) |
 EGU/EGU2017-10440.pdf |
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| Zusammenfassung |
| Mt. Ontake (3067 m.a.s.l.) is a stratovolcano located in central Honsu and around 100 Km
northeast of Nagoya, Japan, with the last eruption occurring on September 27, 2014, killing
57 people, and creating a 7-10 km high ash plume (Kagoshima et. al., 2016). There were no
significant earthquakes that might have warned authorities in the lead up to the phreatic
eruption, caused by ground water flashing to steam in a hydrothermal explosion. At the time
of the eruption there was no operational geochemical surveillance program. In order to
contribute to the strengthening of this program, the Disaster Mitigation Research Center of
Nagoya University and the Volcanological Institute of Canary Islands started a
collaborative program. To do so, an automatic geochemical station was installed at
Ontake volcano and a survey of diffuse CO2efflux and other volatiles was carried
out at the surface environment of selected areas of the volcano. The station was
installed 10.9 km east away from the eruptive vent, where some earthquakes occurred,
and consists of a soil radon (Rn) monitor (SARAD RTM-2010-2) able to measure
222Rn and 220Rn activities. Monitoring of radon is an important geochemical tool to
forecast earthquakes and volcanic eruptions due to its geochemical properties. Rn
ascends from the lower to the upper part of earth’s crust mainly through cracks
or faults and its transport needs the existence of a naturally occurring flux of a
carrier gas. Regarding to the soil gas survey, it was carried out in August 2016
with 183 measurement points performed in an area of 136 km2. Measurements of
soil CO2 efflux were carried out following the accumulation chamber method by
means of a portable soil CO2 efflux instrument. To estimate the total CO2 output,
sequential Gaussian simulation (sGs) was used allowing the interpolation of the
measured variable at not-sampled sites and assess the uncertainly of the total diffuse
emission of carbon dioxide estimated for the entire studied area. The total emission
rate of diffuse CO2 efflux was expressed as the mean value of 100 equiprobable
sGs realizations, and its uncertainly was considered as one standard deviation of
the 100 emission rates obtained after the sGs procedure. Soil CO2 efflux values
ranged from 0.266 gm−2d−1 up to 66.238 gm−2d−1 with an average value of 23.350
gm−2d−1. The estimated average value for the total diffuse CO2 released for the
Mt. Ontake volcanic complex during this study was 3,149 ± 98 td−1, with the
main contributions arising from the NE zone of the complex. It is expected for
future surveys to increase the density of sampling points and to sample the areas
near the crater in order to obtain a better approximation of the diffuse CO2 efflux
emission as well as obtain a long-term evolution to understand the dynamics of
diffuse CO2 emission and its relationship with the volcanic activity of Mt. Ontake. |
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