Integrated Electromagnetic and Geochemical methods applied to volcanic hydrothermal systems: Application to Taal volcano (Philippines) EMSEV-2008, Sinaia, Romania (EMSEV activities: http://www.emsev-iugg.org/emsev/) J. Zlotnicki 1 , Y. Sasai 2 , J.P. Toutain 3 , E.U. Villacorte 4 , A. Bernard 5 , J.M Cordon Jr. 4 , F. Sortino 6 , J. P. Sabit 4 , M. Harada 7 , PHIVOLCS EM team 4 , J. Sincioco 4 , H. Hase 8 , T. Nagao 8 (1) National Scientific Research Centre, OPGC-UMR6524-UBP, France; (jacques.zlotnicki@opgc.univ-bpclermont.fr) (2) The Disaster Prevention Specialist, Tokyo Metropolitan Government (3) LMTG, Observatoire Midi-Pyrénées, Toulouse, France (4) Philippines Institute of Volcanology and Seismology, Philippines (5) Université Libre de Bruxelles, Belgium (6) Istituto Nazionale di Vulcanologia, Palerme, Italy (7) Earthquake Prediction Research Center, Tokai University, Japan (8) Graduate School of Science, Hokkaido University, Japan Supports: EMSEV, IUGG & Associations, PHIVOLCS, French Embassy, CNES, 1 JSPS, EPRC-Tokai Univ., Tokyo Geographical Society
Taal main features • Stratovolcano located at 60 km of Manila • Set in a pre-historical caldera (16 km x 27 km) formed between 140 & 5.4 ky. BP • Volcano Island is 5 km in diameter (311 m high) • 1.2 km diameter crater filled by a 70 m deep lake (MCL) : V~ 45x10 6 m 3 ~8 000 inhabitants are living on the Island 2 About 1M inhabitants are in Taal vicinity
Past activity and casualties Devasted areas VEI 3—5 1749 1911 4 0 km Settlements Latest eruption : 1965 phreato- 1965 magmatic with base surges • Complex of cinders and tuff cones • Destructive eruptions: 1749, 1754, 1911, 1965 • Phreatic (1878, 1911(ashes in Manila), 1970); • Phreatomagmatic (1749, 1965, 1966); strombolian (1968, 1969); plinian (1754) 4 0 km • Deaths 1911: 1334; 1965: 200 3 From E. Corpus
Geological setting and hydrothermal activity SW NE China sea, Taal lake and MCL are almost at the same level Geochemical studies indicate that seawater infiltrates the MCL MCL: mean water temperature: 33°C (100°C locally) MCL: 45x10 6 m 3 in volume MCL: pH~2-3 4 (After Delmelle et al., 1998)
Objectives: How the hydrothermal system controls the volcanic activity? Work plan: – Mapping the hydrothermal system and find out the connection(s) with magmatic source(s), – Evaluation of possible scenarios of a future activity (i.e. sudden phreatic explosions, collapse of crater rims), – Assessment of fluids transfer through the lakes and the volcano. Computation of the heat discharge, – Development of continuous real time multi-parametric monitoring stations and processing, Methodology: Integration of Geophysical (EM) and Geochemical studies, from ground to satellite observations – Self-potential (SP), magnetic (TMF) and magnetotelluric surveys (MT) – Ground soil degassing (CO2), Ground (GTE) and water lake (WTE) tpes & fluxes, WT level changes in the crater lake – Data of ASTER, MOPITT and Demeter satellites – …. 5
Statistics: Towards a new eruption? Mt. Tabaro 1977 eruption Now: 3 eruptions after 31 years (9%) ….. 91% 6
Continuous GPS monitoring Dang Kastila ? MCL 1992-94: Seismic crises, Opening of fissures on the North flank Since 1998 : 1998 2004 Several cycles of inflation and deflation have occurred (2000, 2004) � 120 mm uplift of the volcano centre occurred in Feb.-Nov. 2000 � Mogi models estimate sources between 4.2 and 5.2 km depth 7 After Bartel et al., 2002, 2003
Seismicity 2005 | 2006 20 Kelunji 15 10 5 0 20 J J F M A M J J A S S O N D J F M A M M BM-HF 15 10 5 0 BM-TQ 20 15 10 5 0 CAL-HF 20 Intensity I 15 10 Fault 5 0 20 J F M A M J J A S O N D J F M A M ? CAL-TQ 15 10 5 0 MC-HF 20 15 10 5 0 J F M A M J J A S O N D J F M A M MC-TQ 20 15 Jan 11: Alert Level 1 June 30: Alert Level 0 Nov 23:Alert Level 1 10 5 Data loss 0 � Seismicity seems to take place along a “NW-SE fault” along which dikes could intrude � EQ are ‘regularly’ felt. In Jan., 2005, hundreds of people evacuated for a few days 8 � Alert 1 on a scale of 5 is often set: Oct. 2004, Nov. 2005, Oct. 2006 � mid-2007
Levelling surveys: 06/2004 – 09/2007 Geysering activity 9 PHIVOLCS document
Geysering phenomena in MCL: 15 days in Nov. 2006 Dang Kastila MCL 10 PHIVOLCS document
SP, CO 2 , GT and TMF profiles: 2005 0 200 400 600 800 1000 1200 1400 1600 1800 0 200 400 600 800 1000 100 100 Ground Ground Distance (m) Distance (m) temperature (°C) temperature (°C) 75 75 50 50 25 100 25 5 Active fissures and 4 CO2 50 geothermal field CO2 degassing (%) 3 P4 survey P4 survey degassing (%) 2 4 1 2 50 0 0 0 SP (mV) SP (mV) 0 -100 Topographic effect Active fissures - 1.2 mV/m -50 -200 -100 100 P2 survey P2 survey 200 altitude (m) 75 altitude (m) 50 100 25 Harada et al., 2005 TL shore line Crater rim Distance (m) Distance (m) 0 0 0 200 400 600 800 1000 1200 1400 1600 1800 0 200 400 600 800 1000 P4 P2 11
Satellite thermal mapping : 2007 • ASTER satellite ( Advanced Spaceborne Thermal Emission and Reflection Radiometer ) – Spectral bands : visible (VNIR), near infra-red (SWIR) and thermal infra-red (TIR) – Spatial resolution: 15 m (visible); 90 m (TIR) – Taal lake is taken as temperature reference, comparison with MODIS data (sea) gives a precision of about 0.3°C Jan. 23, 2003 Feb. 27, 2007 Mar. 15, 2007 12 After A. Bernard
SP, CO 2 and GT mappings: 2005-2006 TMF GT CO2 SP SP- TE 13 Zlotnicki et al., 2008
Bathymetry of MCL: 1966 and 2008 2030 40 50 60 70 Ramos, 1988 • A variation of several meters (5 to 10) seems to take place on the northern part of MCL 14 After Harada, provisional document
MCL water temperature: 1m depth Hot spring Fumarole Mean WTE of MCL: 32.7°C (April 2008) GTE & Aster anomalies 15
Magnetotelluric soundings along a S-N cross section Active fissures South North Main crater lake 250 m • 13 soundings (1000-0.1 Hz) 250 m • 2 km long section 1500 m bsl 16
Temperature gradients and CO 2 fluxes: Feb. 2007 0 10000 y = 3E-05x 3.7819 1000 -10 G15 Δ T (°C/m) 1210 °C m -1 depth (cm) 100 -20 10 -30 1 20 40 60 80 100 -40 G12 T 10 °C k=1 W°C -1 m -1 39 °C m-1 Heat Flow : DAK: 2 MW -50 Heat discharge MCL: 7.3 MW 20 40 60 80 100 � 15 MW temperature (°C) in MCL: ~7.5 MW 10 Fl (L/m2/mn) DK ф CO 2 (L m -2 mn -2 ) Fl (L/m2/mn) MCL 1 Higher ∇ T 0.1 Higher CO 2 fluxes take place in MC 0.01 0.001 1 10 100 1000 10000 Δ T (°/m) 17 After Toutain After Toutain
Possible centre of the next activity & scenario Active fissures crater Suspected Every day about 100 to 200 persons Every day about 100 to 200 persons fault 18 climb the volcano climb the volcano
HYDROTHERMAL ACTIVITY DURING THE PAST YEARS 19
Repeated magnetic surveys: 2005-2007 Area B Alert Geyser Area C Area A 20
Repeated SP, CO2, GTE Surveys: 2005-2007 21
Aster thermal imaging and time evolution:2001-2007 22 After A. Bernard
TRANSIENT SIGNALS RELATED TO SEISMIC CRISES 23
Magnetic signals related to Jan. 2005 seismic crisis 2005 CAL-HF 20 15 10 5 0 20 J F M A M J J Q 20 MC-HF 15 10 5 0 J F M A M J J Q 20 Spontaneous evacuation of the Islanders in the night Alert 1 was set 24
TMF Modeling N Demagnetized triaxial ellipsoid at shallow depth (50 & 10 m) obtained 25 by a increase of few degrees Harada et al., 2005
Transient SP and GT anomalies evidenced by repeated surveys 26
Transient SP, CO 2 and GT anomalies: 2007 2 � Alert 1.x 1.8 1.6 1.4 P4 1.2 1 Geysering 0.8 0.6 activity 0.4 0.2 0 7 7 7 7 7 7 7 7 7 7 7 7 8 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 / / / / / / / / / / / / / / 1 2 3 4 5 6 7 8 9 0 1 2 1 2 0 0 0 0 0 0 0 0 0 1 1 1 0 0 / / / / / / / / / / / / / / 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 February 2007 April 2007 0 200 400 600 800 0 200 400 600 800 100 100 Weak Distance (m) Distance (m) Ground Ground bubbling area 75 temperature (°C) 75 temperature (°C) P4 survey P4 survey 50 50 SP-GTE 100 100 25 25 anomalies Active fissures and Active fissures and CO2 75 CO2 75 geothermal field geothermal field degassing (% ) degassing (% ) 50 50 20 20 15 15 10 10 5 5 100 0 100 0 50 50 SP (mV) SP (mV) 0 0 -50 -50 -100 -100 -150 250 -150 250 200 200 altitude (m) altitude (m) 150 150 100 100 Crater rim MCL shore line 50 50 Crater rim MCL shore line Distance (m) Distance (m) 27 0 0 0 200 400 600 800 0 200 400 600 800
SETTING CONTINUOUS MULTI-PARAMETRIC STATIONS 2006 - 2008 28
Continuous SP, GTE, Rn and TMF stations crater TMF 2006 2007 2006 2007 The 2 stations are telemetered to the local observatory 29
Ground temperature gradient in MCL N C W 2 1.8 Mag Earthquakes 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 MCL station 01/01/07 01/02/07 01/03/07 01/04/07 01/05/07 01/06/07 01/07/07 01/08/07 01/09/07 01/10/07 01/11/07 01/12/07 30
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