  //  (,*+*)
 -  +//ῌ+0- *+),-ῐῒ῎ῌ῍῏῔ῑΐ¼  ½  ,,*+* & / L 0 '() ,*+* & / L ,2 '(Thermal Measurement and Monitoring on Volcanoes
Akihiko TERADA(,((+    

MN ,**3 &*()'O*++,-(-P. /0 (Yamamoto

et al., +333) QRST9U (Mori et al., ,**2) 1

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203ῌ+.*. !" "# /,2*$''0'*+12'*+3()*+,-./
Aso Volcanological Laboratory, Kyoto University, /,2*
Kawayo, Minami-Aso, Kumamoto 203ῌ+.*., Japan.
 -11ῌ+1++   0.+ῌ-04()5 

$%&'()*+,-./
Volcanic Fluid Research Center, Tokyo Institute ofTechnology, 0.+ῌ-0 Kusatsu, Agatsuma, Gunma -11ῌ
+1++, Japan.
Corresponding author : Akihiko Terada
e-mail : terada@ksvo.titech.ac.jp  

156

Fig. +. (a) Aerial photograph of the Nakadake Craters. SWF : fumaroles within the south wall. (b) Schematic
model of mass ﬂow (after Terada et al., submitted) around the +st Crater of Nakadake, Aso volcano,during a non-eruption period. Superscript numbers refer to the following references : [+] Yamamoto etal. (+333) ; [,] Takagi et al. (,**0) ; [-] Tanaka (+33-) ; [.] Kanda et al. (,**2) ; [/] Miyabuchi andTerada (,**3) ; [0] Mori et al. (,**2). The topography data are from Kokusai Kogyo Co., Ltd.

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Fig. ,. (a) The automatic image recording system in operation at the crater rim site. This ﬁgure is modiﬁed
from Figure ,a of Terada et al. (,**2a). (b) Photograph of a rope run around the +st Crater. The
main rope used in deploying the water telemetry buoys was stretched between sites on the western andeastern parts of the crater rim. (c) Photographs of the temperature telemetry buoy. The buoy descends
to the lake surface under gravity along the main rope made of polypropylene. (d) Photographs of thesampler used to collect lake sediments and dredged lake sediments. This ﬁgure is modiﬁed from Figure +of Miyabuchi and Terada (,**3).

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Fig. -. Observed temperature data and computed watertemperature as a function of time using a numericalmodel (after Terada et al., submitted). Five setsof calculation results are shown for enthalpy ofbottom input ﬂuids of +.0, ,.*, ,.., ,.2 and -.,MJ/kg, respectively.

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159

Fig. .. Bar graphs of (a) yearly averaged mass and (b) energy budgets in Yudamari crater lake, calculated
based on the temporal variations of ﬂux and enthalpy of the bottom input ﬂuids from July ,**0 to
January ,**3 (after Terada et al., submitted). Evaporation (Fr) and (Fo) represent free and forced
convective energy. (c) Mass ﬂuxes of liquid water and (d) high-temperature volcanic gas, assuming
temperatures of +** and 2**, respectively. (e) Monthly precipitation measured at Aso weather
station. (f) Daily mean amplitude of continuous volcanic tremors observed at a permanent JMA (Japan
Meteorological Agency) seismic station located 0** m west of Yudamari.

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Fig. /. Values of water temperature T (color) andspeed of dimensionless water level change (contours) for which a lake system attains an equilibrium state in energy calculated by a numericalmodel (after Terada and Hashimoto, submitted).
Enthalpy and ﬂux of bottom input ﬂuid aredeﬁned by H* and m* respectively ; S* ischaracteristic area of lake surface. In Section.ῌ,ῌ+, the behavior of water temperature andwater level are discussed with reference toarrows a and b. In these calculations seepage
output and precipitation inﬂow are negligible
relative to the bottom input mass. Crater topography is assumed to be cylindrical shape.

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161

Fig. 0. (a) Example of the placement of Ice Boxes. To measure heat-discharge rate, Ice Boxes were placedon the ground surface. To correct heat ﬂow due to sunlight and ambient air we placed an Ice Box on athermal insulation mat close to the original measurement sites. Temporal changes of (b) groundtemperature at +* cm depth and (c) heat-discharge rate (kW/m,) obtained at Usu volcano on ,. April,**3. Small dots represent each measurement, whereas the open circles represent areal means. (d) Plotof heat-discharge rate (kW/m,) versus ground-surface temperature (). The dotted line indicates thebest-ﬁt line obtained using the least squares method, taking all data into account.

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.89+ :/;/</=>?-, ,--ῌ,.*.
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n; opqrs?t:;<= (,**3) Kukkvw)*x y(z{|}~

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