Recurring non-eruptive unrest at Taal (Philippines)

R.U. Solidum, E.P. Laguerta and Taal Monitoring TeamPhilippine Institute of Volcanology and Seismology

(PHIVOLCS)

Volcano Observatory Best Practices Workshop: Near-term Eruption Forecasting

11-15 September 2011

Introduction to PHIVOLCS – major activities

• Monitoring, warning and advisory services on volcanic and earthquake hazards, including tsunami- national seismic network

- 6 volcano observatories

• Hazard mapping and risk assessment services

• Research and development

• Disaster preparedness and risk mitigation services

Introduction to PHIVOLCS – links (some)

• Member of the Technical Working Group of the Disaster Risk Reduction and Management Councils (DRRMC) at National level and Regional to Provincial Level if present in area

• Office of Civil Defense (OCD)

• Local governments

• Key government agencies – land use and development planning; local governance; education

• Non-government organizations

• Media

Tectonic Setting of the Philippines

~300 volcanoes:

• 23 active

• 26 potentially active

Taal Caldera

Metro Manila

Taal Lake

Volcano Island

Main Crater LakeTaal Caldera

Tagaytay City

South China Sea

Historical Eruptions at Volcano Island

• Main Crater (1572, 1591, 1605-1611, 1634, 1635, 1641, 1645, 1749, 1754, 1790, 1808, 1825, 1842, 1873, 1874, 1878, 1903, 1904, 1911)

• Binintiang Malaki (1707, 1715)

• Binintiang Munti (1709, 1729)

• Pira-piraso (1731)

• Off Calauit (1716)

• Mt. Tabaro (1965, 1966, 1967, 1968, 1969, 1970, 1976, 1977)

• 33 eruptions since 1572• latest eruption: October 1977

Historical Eruption Sites

1754 (15 May-30 Nov) – Main Crater; Plinian; VEI 4; ?dead

1911 (27 Jan- 7 Feb) – Main Crater; Phreatic; VEI 3; 1335 dead

1965 (28 to 30 Sep) – Mt. Tabaro; Phreato-magmatic; VEI 4; ~200 dead

Some Destructive eruptions of TaalSome Destructive eruptions of Taal

Taal base surge, 1965

Tagaytay City

BalayanCalaca

Agoncillo

Lemery

Taal

Old Tanauan

Old Lipa

Mt. Batulao

Mt. MakulotOld Taal

Areas affected by 1754 base surge

Data Sources:Arboleda and Ruelo, (1986); Torres, (1989) 0 20

kilometers

Eruption site

Areas affected by base surges (1754)

Areas affected by base surges (1911, 1965)

1911

0 4km

Eruption site

1965

0 4km

Eruption site

Areas affected by base surgesData Sources:Pratt (1911); Worcester (1912); Moore, Nakamura and Alcaraz, (1966); Moore (1967); Arboleda and Ruelo, (198x)

Base Surge Hazard Map

At risk: ~5000 people on Volcano Island at least 100,000 people around Taal Lake

ALERT LEVELS RESPONSE

Alert Level 1 Main Crater is off limits to the public because sudden explosions may occur or toxic gases may accumulate. Volcano Island residents and visitors must be aware and vigilant of the volcano’s condition.

Alert Level 2 Main Crater, Daang Kastila and 1965-1977 Mt. Tabaro Eruption Site are off limits to the public.

Selective evacuation – women, children and elderly at the Volcano Island are advised to transfer to their relatives at the mainland.

Alert Level 3 Total evacuation of the Volcano Island.

Alert Level 4 Flank eruption – lakeshore barangays facing eruption sitel

Eruption site: Main Crater – lakeshore barangays of Talisay, Tanauan, Agoncillo, Balete, San Nicolas and Laurel.

Additional areas to be evacuated shall be determined based on the development of escalating activity and possible location of eruption site.

Alert Level 5 Expansion of risk areas depending on the magnitude of eruption.

Response Action Based on Alert Level

Taal Volcano Seismicity (1990-1999)

Pira-piraso Station

Taal Volcano Seismicity (2000-2011)

Description of some unrest in Taal• 1991 Mar to Jul - increased seismicity up to 45 VT events/day; some felt at Intensities I-V; intense bubbling at Main Crater Lake (MCL); geysering at MCL; lake T increased by 2C

• 1992 Feb 14-28 - dramatic increase in seismicity with 2550 VT events within 24hrs, several were felt; decreased to baseline within 2 weeks; Volcano Island uplifted up to 20cm; fissuring at northeastern slopes; intense bubbling at MCL; lake T increased by 2C (Alert level 2 then 3 – evacuation of Volcano Island)

• 1994 Mar 11-31 - escalating increase in seismicity with 1550 VT events within 24hrs, several were felt at Intensities I-II; inflation of Volcano Island up to 16cm; fissuring at eastern slopes; intense bubbling at MCL; lake T increased by 5C (Alert level 3 – evacuation of Volcano Island)

SUMMARY OF SEISMIC SWARMS/UNRESTS AT TAAL VOLCANO

Description of some unrest in Taal

• 2010 Apr - June - increase in VT events, several were felt; slight inflation of Volcano Island; bubbling at MCL; lake T increased by 2-3C; increased steaming at Crater Lake (Alert level 2 - Main Crater off limits)

• 2011 Apr-May – increase in VT events, several felt at Intensities I-III; quakes from 4km to 1km beneath Volcano island; preceded by CO2 flux of 4600 t/d in late March, 4 times background measurement (Alert level 2 – Main Crater off limits)

Taal Volcano Seismicity (2005, 2008, 2010, 2011)

Precise Leveling at SE slope

CO2 flux from ITER (Spain)-PHIVOLS collaborationGraph from Arpa et al, 2011

CO2 Flux (2008-2011)

Communication of Forecast(via fax, email, web, phone)

PHIVOLCSHQ

OCDNational

OCDRegion

DRRMC

ProvinceDRRMC

City/TownDRRMC

VillageDRRMCPublic

PHIVOLCSObservatory

NDRRMCHead

OP

MediaNational

MediaLocal

NDRRMCMembers

VAACTokyoDarwin

CAAPNational

Local

Met OfficeNational

Local

CAAP – Civil Aviation Authority of the PhilippinesNDRRMC- National Disaster Risk Reduction and Management CouncilOCD – Office of Civil DefenseOP- Office of the President

Awareness and Preparedness Activities(Town of Laurel – 2008)

Village Captain

Civil Defense Director

Awareness and Preparedness Activities(Village of Bilibinwang, Agoncillo – 2008)

Some on-going initiatives for Taal• Improvement of monitoring systems:

- seismic telemetry (currently 8 stations: 4SP, 4BB) - deformation (currently 3cGPS, one e-tilt; precise leveling,

EDM) - electromagnetism - gas geochemistry (CO2) - Main Crater Lake observations (chemistry, T)* With international partners from NIED and Japanese

institutions (JICA-JST), EMSEV Group, ITER (Spain), others?

• Awareness and preparedness at local level with province and OCD Region

• Advocacy for appropriate land use and developmentplanning

THANK YOU!

www.phivolcs.dost.gov.phPHIVOLCS Building, CP Garcia Ave.UP Campus, Diliman, Quezon City

Tel 426-1468; Fax 9298366