IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

1A2_2D-O12

Room B1

Date/Time: July 21 12:00-12:15

Recent activity of Taal volcano (Philippines) inferred by electromagnetic and othergeophysical monitoring networks: 2009-2012
Jacques Zlotnicki1 , Yoichi Sasai2 , Malcolm Johnston3 , Frederic Fauquet4 , Egardo U. Villacorte4 , Paul
Karson B. Alanis4 , Paolo R. Reniva4 , Juan Cordon Jr4 , Toshiyatsu Nagao2 , Mariton Bornas4
1

CNRS ; UMR6524-OPGC-UPB, 63177 Aubiere cedex, France, 2 Tokai University, Japan, 3 US
Geological Survey, Menlo Park, USA, 4 PHIVOLCS, Quezon City, Philippines
E-mail: jacques.zlotnicki@wanadoo.fr

Taal volcano in the Philippines is a particularly hazardous volcano in a very populated region near the capital,Manila. Repeated pyroclastic flows, base surges and violent phreatic explosions, such as experienced during theprevious 33 historical eruptions, threaten the region. Since the last long eruptive episode in 1965-1977, Taal volcano
has exhibited sporadic and intense seismic activity, ground deformation, and surface activity. The monitoring ofthe volcano is one of highest priorities of the Philippines Institute of Volcanology and Seismology (PHIVOLCS,http://www.phivolcs.dost.gov.ph/). Since 2004, the Inter-Association Working Group on ’Electromagnetic Studies
of Earthquakes and Volcanoes’ (EMSEV, http://www.emsev-iugg.org/emsev/) and PHIVOLCS have developed ajoint research program for (1) understanding the interactions between the magma feeding system, the hugehydrothermal system located beneath the volcanic Island, and ground water recharge by seasonal rainfall in theinner Main Crater Lake and the external Taal Lake and (2) building up real-time monitoring networks based onelectromagnetic and other geophysical methods.
We will focus this presentation on methods we use for monitoring the volcano and results we have obtained during
the recent activity of Taal. In late April 2010, after a few years of relative quiet, the volcano experienced accelerated
deformation and dramatically increasing microseosmicity. This caused PHIVOLCS to temporarily raise the volcano
alert level to two on a five level scale. Four periods of high seismicity were recorded from April to July 2011. The
2010 seismic crisis was accompanied by ground deformation, and re-opening of active East-West fissures locatedon the northern flank of the volcano. Electric, magnetic and temperatures changes were associated with the 2010seismo-volcanic crisis.
One hypothesis is that this crisis started as a result of magma intrusion at about 5-km depth under the north sideof the Main Crater Lake. Injection of volcanic fluids into the hydrothermal reservoir could have caused the inflationand seismicity observed from April to June, 2010. As activity receded in the following months, some shrinkage ofthe reservoir could have occurred. No noticeable surface or deep activity was subsequently observed in 2011 but,after one year of low activity, the seismicity has been again increasing since October 2012.
Since 2011, EMSEV has focused on increasing the monitoring capability on the volcano. Continuous Self-potential,
magnetic, tilt, ground temperatures, resistivity measurements are made every two seconds at four stations on thevolcano and data are radio-transmitted in real-time to the local Buco observatory.

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