ῒ῔  /+  (,**0) .  ,1-ῌ,2, ΐ ῕MODIS ῍ῌ,**.ῌ,**/,**0  +  +0  ,**0  /  +3 

Thermal Surveillance of the Asama ,**.ῌ,**/ Activity Using MODISNighttime Infrared Images
Takayuki KANEKO῍, Kenji TAKASAKI῍, Atsushi YASUDA῍ and Yosuke AOKI῍
Asama volcano, located in the central part of Japan, repeated medium to small scale Vulcanian eruptions,from September through December ,**.. We analysed the activity between January ,**. and April ,**/ usingnighttime infrared data from MODIS -Moderate Resolution Imaging Spectroradiometer -onboard Terra and Aqua
satellites, in conjunction with the data from ground-based instruments obtained simultaneously and chemicalcomposition of the ejecta. The observed period is divided into four stages, S-I, S-II, S-III and S-IV, based on therelationship between thermal anomalies observed by MODIS and eruptive activity. S-I (second half of August)is the thermally active period preceding to the series of eruptions. This may have been caused by a magmaticsupply to the shallow level of the conduit, resulted from dyke intrusion at a deep level (+ km bellow sea level) in
July, as suggested by the ground deformation monitoring. This magmatic supply probably resulted in initiating
the eruptive activity of S-II. S-II (+ September -mid-December) is the thermally active period during the seriesof eruptions, which is sub-divided into two stages, S-IIa (+ September -+* October) and S-IIb (+* October-mid-December), by the two thermally active pulses in this period. Similar pulses are also recognized in thetime-series variation of eruptive amount of S-II, as well as seismicity and SO, discharge rate. A deep dyke
intrusion observed in the late S-IIa may have resulted in a new supply of magma to the shallow level, which caused
the IIb activity. After two months of inactive period of S-III(late December ,**. - February ,**/), S-IV
(March-at least April ,**/), the post eruptive thermally active period, started. Although this stage did not
involve eruptive activities, SO, discharge rate, level of volcanic glow and height of plume raised. This may havebeen caused by the third magmatic supply to the shallow level in late January. At the volcanoes possessing open
to semi-open passages between the summit crater and shallow level of the conduit like Asama, MODIS may detect
pre-eruptive thermal anomaly, which can be utilized for monitoring those distributing in remote areas, such as
east Asia.
Key words : MODIS, Asama volcano, thermal analysis, infrared, remote sensing+ῌ ῐ ῎ ῑ῏!"#$%&'%()*+,-.ῌ/0/1234ῌ58Ug5* hA/0/AH[ij klAmn
opUqrdY12s9Uop5t[ juvABC

6789:*;<=>? 6@AB

DE5op:*VR&>*S wxy B\]58Uz

CDE FAGHDIJK*L=MN3OPQR3*S{dY|Z } ~ +321 ; Dehn et al., ,**, >*e8AT/0/5 6U89:*VRUWXYZ[3B:*;f (Wooster and Rothery, +331 ; Wooster,\]5^_*S `a /0/5bc89d3e;f=&,**+) 8U^:*;f  2  ,**-

++-ῌ**-, ¡¢£¤¢¥¦^ +ῌ+ῌ+¡¢Z§ ¨<Earthquake Research Institute, University of Tokyo,+ῌ+ῌ+ Yayoi, Bunkyo-ku, Tokyo ++-ῌ**-,, Japan.

34 3 5P()Ye*S VAW3B

Corresponding author : Takayuki Kaneko
e-mail : kaneko@eri.u-tokyo.ac.jp

op$% U hA/0/AH[iklADEJK*VR5=[)y 8A^iGHJ:*L=MN35$?R3*S d$d35% w5
3 C33()Ye3eS B\]AOPJ8KUG:*'U _ J