2.16
MONITORING OF VOLCANIC ACTIVITY IN TAAL VOLCANO
(PHILIPPINES)BY ELECTROMAGNETIC METHODS: GEOMAGNETIC
OBSERVATIONS.
Makoto Harada 1) , Julio P. Sabit 2) , Yoichi Sasai 3) , Juan M. Cordon Jr. 2) , Jacques
Zlotnicki 4) , Yoshikazu Tanaka 5) , Edgard U. Villacorte 2) , Hideaki Hase 6) ,
Jame S. Sincioco 2) and Toshiyasu Nagao 1)
1) Earthquake Prediction Research Center, Institute of Ocean Research and Development,
Tokai University, 3-20-1, Orido, Shimizu-ku, Shizuoka 424-8610, Japan.
E-mail: mharada@scc.u-tokai.ac.jp
2) Philippine Institute of Volcanology and Seismology, C. P. Garcia Avenue, U. P. Campus,
Diliman, Quezon City, the Philippines.
3) Disaster Prevention Division, Tokyo Metropolitan Government, 2-8-1, Nishi-Shinjuku,
Shinjuku-ku, Tokyo 163-8001, Japan.
4) CNRS, Observatoire de Physique du Globe de Clermont-Ferrand, 24 Avenue des Landais
63177-AUBIERE Cedex, France.
5) Aso Volcanological Laboratory, Kyoto University, 5280, Kawayo, Minami-Aso,
Kumamoto, 869-1404, Japan.
6) Institute of Seismology and Volcanology, Hokkaido University, Kita-10, Nishi-8, Kita-ku,
Sapporo, Hokkaido 060-0810, Japan
We have carried out electromagnetic (EM) monitoring of Taal Volcano, the Philippines. Taal is a basaltic-andesite volcano which has had many eruptions and is located close to Metro
Manila. On Taal, various geophysical and geochemical observations have been conducted, but not the EM monitoring. A cooperative project for EM studies between PHIVOLCS and
EMSEV/IUGG has recently been started. Measurements of total magnetic field (TMF), selfpotential (SP), ground temperature and CO
2
degassing were made during the first survey in
January 2005. Distinct anomalies in TMF and SP were found in the geothermal areas in Taal.
Repeated survey in February detected changes in TMF up to 10 nT and enhancement of positive SP anomaly during the one and half-month period, when the surface geothermal activity was high. Field campaigns have been conducted 11 times by April 2008. Continuous measurements were started on SP, ground temperature, and TMF in the geothermally active areas in the Volcano Island. Moreover, the bathymetry, TMF, water temperature and CO
2 concentration on the surface of the Main Crater Lake were measured in April, 2008. These combined measurements of EM techniques will contribute to clarifying the eruption mechanism and the magma plumbing system of Taal Volcano, which will lead to the prediction of volcanic eruption.