DEVELOPMENT DEVELOPMENT OF OF

SEISMOLOGICAL OBSERVATION NETWORK SEISMOLOGICAL OBSERVATION NETWORK IN THE IN THE

PHILIPPINESPHILIPPINESEnrico A. Mangao

Philippine Institute of Volcanology and Seismology (PHIVOLCS)

• SUMMARY

• Since the establishment of its seismological stations in 1948, the Philippines has developed at a rather slow pace, from 8 to 35 stations in more than 50 years. But this maybe understandable as the country had other priorities in poverty alleviation, health, and education. However, the increasing number of volcano and earthquake related disasters, local and international, did not fail to alarm the populace including the national leadership. They have come to realize that the hazards posed by earthquakes and volcano eruptions are for real and something will have to be done to understand their possible effects and somehow mitigate their impacts.

• In the last few years, with the help of Japan International Cooperation Agency(JICA), the Philippines have undergone radical improvementｓ in its volcano and seismological observation. Having installed additional instruments to complement the 35 volcano and seismic stations, the project almost doubled this number using telemetry stations operated-on via satellite.

•• INTRODUCTIONINTRODUCTION

►► Seismological studies in the Philippines date back to colonial tSeismological studies in the Philippines date back to colonial times imes when the Jesuit fathers, in cooperation with the Weather Bureau,when the Jesuit fathers, in cooperation with the Weather Bureau,operated a seismograph station from 1890 onwards. Seismologists operated a seismograph station from 1890 onwards. Seismologists associated with this station kept careful records of felt earthqassociated with this station kept careful records of felt earthquakes uakes and one of them, Fr. Repetti, published a comprehensive list of and one of them, Fr. Repetti, published a comprehensive list of felt felt earthquakes and their impacts beginning in the latter part of thearthquakes and their impacts beginning in the latter part of the e sixteenth century and continuing up until 1959. sixteenth century and continuing up until 1959.

►► Today, the Philippine Institute of Volcanology and Seismology Today, the Philippine Institute of Volcanology and Seismology ((PHIVOLCSPHIVOLCS) is the main organizational body mandated to study ) is the main organizational body mandated to study earthquakes, following the transfer of the seismological functioearthquakes, following the transfer of the seismological function from n from PAGASAPAGASA in 1984. PHIVOLCSin 1984. PHIVOLCS’’ principal objectives are to avert disasters principal objectives are to avert disasters and mitigate hazards from geotectonic processes. One of its and mitigate hazards from geotectonic processes. One of its programs, the Seismological Observation and Earthquake Predictioprograms, the Seismological Observation and Earthquake Prediction, n, is geared towards increasing our understanding of the causes, efis geared towards increasing our understanding of the causes, effects, fects, nature and physics of earthquakes and earthquake zones in the nature and physics of earthquakes and earthquake zones in the country. This includes related events such as tsunami, liquefactcountry. This includes related events such as tsunami, liquefaction, ion, landslides and faulting. landslides and faulting.

•• PLATE TECTONICSPLATE TECTONICS

►► The Philippines, lying between two major The Philippines, lying between two major tectonic plates and with active faults tectonic plates and with active faults crisscriss--crossing the archipelago, is one of the more crossing the archipelago, is one of the more seismically active countries in the world. The seismically active countries in the world. The northwestward moving pacific plate is northwestward moving pacific plate is presently pushing the Philippine sea plate presently pushing the Philippine sea plate beneath the eastern side at the rate of about beneath the eastern side at the rate of about 7 cm. per year. 7 cm. per year.

The oceanic parts of the slowThe oceanic parts of the slow--moving Eurasian plate are moving Eurasian plate are being subducted along the western side of Luzon and being subducted along the western side of Luzon and Mindoro islands at the rate of 3 cm. per year. The Mindoro islands at the rate of 3 cm. per year. The southeastward component of the Eurasian plate motion is southeastward component of the Eurasian plate motion is now sustaining the active collision of the continental block now sustaining the active collision of the continental block of Palawan with Mindoro, and of the northern sections of of Palawan with Mindoro, and of the northern sections of the Zamboanga peninsula with western Mindanao.the Zamboanga peninsula with western Mindanao.

These plate interactions and movements along the active These plate interactions and movements along the active faults are responsible for the presentfaults are responsible for the present--day high seismicity day high seismicity of the Philippine archipelago.of the Philippine archipelago.

►► At least five earthquakes per day At least five earthquakes per day occur in the Philippines. Based on occur in the Philippines. Based on the distribution of epicenters, the the distribution of epicenters, the most seismically active part of the most seismically active part of the country is its eastern section country is its eastern section containing eastern Mindanao, containing eastern Mindanao, SamarSamarand and LeyteLeyte with an average of 16 with an average of 16 perceptible earthquakes per year. perceptible earthquakes per year. This is due to the active This is due to the active subductionsubductionprocess going on along the Philippine process going on along the Philippine Trench. Trench.

►► The other relatively active parts are The other relatively active parts are found at the western side of found at the western side of Northern Luzon and the area in the Northern Luzon and the area in the vicinity of vicinity of LubangLubang Island and Island and Mindoro. The presence of the East Mindoro. The presence of the East Luzon Trench, Luzon Trench, CasiguranCasiguran Fault and Fault and the northern segment of the the northern segment of the Philippine Fault Zone all make the Philippine Fault Zone all make the places at and near places at and near DingalanDingalan Bay and Bay and CasiguranCasiguran earthquakeearthquake--prone. The prone. The high frequency of earthquakes in the high frequency of earthquakes in the offshore areas of offshore areas of LubangLubang Island and Island and northern Mindoro may be due to the northern Mindoro may be due to the activities of the activities of the LubangLubang Fault. Fault.

•SEISMICITY

••Philippine Destructive Earthquakes and Their ImpactsPhilippine Destructive Earthquakes and Their Impacts

4304307878777.17.1VIIIVIIINorth of Mindoro North of Mindoro IslandIsland

15 November 199415 November 1994

2,7862,7861,2831,28335357.87.8VIIIVIIIRizalRizal, , NuevaNueva EcijaEcija16 July 199016 July 1990

8,0008,0003,7393,73930307.97.9VIIVIIMoro Gulf, Moro Gulf, MindanaoMindanao

17 August 197617 August 1976

100100SS141433337.07.0VIIVIIRagayRagay Gulf, Gulf, BicolBicol17 March 197317 March 1973

200200151540407.37.3VIIVIIBaler, QuezonBaler, Quezon07 April 197007 April 1970

60060027027052527.37.3VIIVIICasiguranCasiguran, Aurora, Aurora02 August 196802 August 1968

71371329129196967.67.6VIIVIILanaoLanao del del SurSur, , MindanaoMindanao

01 April 195501 April 1955

101101131360606.56.5VIIVIIBacon, Bacon, SorsogonSorsogon02 July 195402 July 1954

InjuredInjuredCasualtyCasualtyDepth Depth kmkm

Surface Surface MagnitudeMagnitude

IntensityIntensityEpicenterEpicenterDateDate

••NETWORKNETWORK

►► As the Jesuit order from its headquarters in As the Jesuit order from its headquarters in AteneoAteneo de Manila University de Manila University continues to operate three seismograph stations, continues to operate three seismograph stations, the the Philippine Weather Philippine Weather BureauBureau ((now now PAGASAPAGASA)) began to operate seismograph stations on its own in began to operate seismograph stations on its own in 1948 and had a network of eight stations. With the exception of 1948 and had a network of eight stations. With the exception of the principal the principal station in Diliman, Quezon City, the instruments were located atstation in Diliman, Quezon City, the instruments were located atmeteorological stations where the rock is not suitable for highmeteorological stations where the rock is not suitable for high--magnification magnification operation. For this reason, the instruments all operated at lowoperation. For this reason, the instruments all operated at low--magnification magnification operation, in the 1000 to 5000 range.operation, in the 1000 to 5000 range.

►► In the middle of 1970In the middle of 1970’’s, with the improvement of roads and the availability of s, with the improvement of roads and the availability of electric power, PAGASA was able to find quiet locations for seielectric power, PAGASA was able to find quiet locations for seismic smic observation. It was at this time that the observation. It was at this time that the UNESCOUNESCO established its seismic established its seismic network in the country under the Regional Seismological Network network in the country under the Regional Seismological Network for South for South East Asia Project. PAGASA have established seven new stations wiEast Asia Project. PAGASA have established seven new stations with th equipment provided by UNESCO and funded by the United Nations equipment provided by UNESCO and funded by the United Nations Development Program (Development Program (UNDPUNDP). ).

►► The project has maintained 11 stations, eight of which were newlThe project has maintained 11 stations, eight of which were newly y established while the rest were renovations of the old buildingsestablished while the rest were renovations of the old buildings. The new . The new instruments were instruments were KinemetricsKinemetrics short period seismographs with magnification short period seismographs with magnification range from 28,000 to 225,000 at 0.3 seconds, and using range from 28,000 to 225,000 at 0.3 seconds, and using Ranger Seismometer Ranger Seismometer SSSS--11. Old stations used . Old stations used Teledyne Teledyne GeotechGeotech with Swith S--13 seismometers, or the 13 seismometers, or the HosakaHosaka 33--component smokecomponent smoke--type instruments. It was on this settype instruments. It was on this set--up when the up when the seismological function was assumed by PHIVOLCS.seismological function was assumed by PHIVOLCS.

►► A f t e r t h e A f t e r t h e L u z o n L u z o n Earthquake of 1990Earthquake of 1990 , , PHIVOLCS realized the PHIVOLCS realized the necessity of establishing a necessity of establishing a denser network to monitor denser network to monitor e a r t h q u a k e s m o r e e a r t h q u a k e s m o r e quantitatively. Although quantitatively. Although far from being ideal, far from being ideal, P H I V O L C S h aP H I V O L C S h aｄｄ 3 5 3 5 permanent stations and permanent stations and six telemetry stations by six telemetry stations by 1995. Except for a strong 1995. Except for a strong period seismograph in the period seismograph in the main office, all the other main office, all the other stations had purely short stations had purely short period seismographs. With period seismographs. With t h i s s e tt h i s s e t -- up we have up we have accumulated a larger accumulated a larger earthquake database and earthquake database and the quality of epicenter the quality of epicenter locations have improved locations have improved c o n s i d e r a b l yc o n s i d e r a b l y . .

Palo Seismic Station

•• JICA PROJECTJICA PROJECT

►► In 1998, In 1998, Japan International Cooperation AgencyJapan International Cooperation Agency ((JICAJICA) and ) and PHIVOLCS began exploratory talks on improving the seismological PHIVOLCS began exploratory talks on improving the seismological and and volcano observation of the Philippines using statevolcano observation of the Philippines using state--ofof--thethe--art instruments art instruments to be provided for by the government of Japan through JICA. In to be provided for by the government of Japan through JICA. In 1999, 1999, the Phasethe Phase--I of the JICA project has commenced. I of the JICA project has commenced.

•• InstrumentsInstruments

►► In 2000, new instruments have already been setIn 2000, new instruments have already been set--up in all 35 stations. up in all 35 stations. These stations were equipped with the These stations were equipped with the KelunjiKelunji--D seriesD series digital digital seismograph recorder with 3seismograph recorder with 3--component accelerometer (component accelerometer (GeotechGeotech PAPA--22), 22), and 3and 3--component seismometer (component seismometer (GeotechGeotech S13S13--J). In addition, Baguio and J). In addition, Baguio and Tagaytay stations have 3Tagaytay stations have 3--component broadband seismometer (component broadband seismometer (GuralpGuralpCMGCMG--3T). 3T).

► By 2004, PhasePhase--II of the JICA Project have been installed. PHIVOLCS is II of the JICA Project have been installed. PHIVOLCS is currently operating 29 manned and 29 satellitecurrently operating 29 manned and 29 satellite--fed seismic stations. It fed seismic stations. It also operates 9 broadband stations and maintains 6 Metro Manila also operates 9 broadband stations and maintains 6 Metro Manila telemetry seismic stations.telemetry seismic stations.

Philippine Philippine NetworkNetwork

20042004

► 29 Manned Stations► 29 Unmanned Stations► 6 Volcanological Observatories► 6 Metro Manila Seismic Telemetry► 10 Metro Manila Strong Motion

Stations

••Unmanned StationUnmanned Station

OutsideOutside

InsideInside

•• INTERNATIONALINTERNATIONAL COOPERATIONSCOOPERATIONS

►► The Disaster Prevention and Research Institute (DPRI) of KyoThe Disaster Prevention and Research Institute (DPRI) of Kyoto University of to University of Japan, maintains three broadband recording systems in Luzon sincJapan, maintains three broadband recording systems in Luzon since 1997. STSe 1997. STS--1 is 1 is installed in Baguio City, while the STSinstalled in Baguio City, while the STS--2 seismometers are installed in Palayan City 2 seismometers are installed in Palayan City and in Guinayangan, Quezon. This undertaking is under the Ocean and in Guinayangan, Quezon. This undertaking is under the Ocean Hemisphere Hemisphere network Project (OHP) which aims to investigate the structure annetwork Project (OHP) which aims to investigate the structure and dynamics of the d dynamics of the EarthEarth’’s interior. s interior.

►► The Global Alliance of Regional Networks (GARNET) was introdThe Global Alliance of Regional Networks (GARNET) was introduced in the uced in the Philippines in early 1998, using the telemetry network of PHIVOLPhilippines in early 1998, using the telemetry network of PHIVOLCS located CS located around the vicinity of Metropolitan Manila area. The primary goaaround the vicinity of Metropolitan Manila area. The primary goal of GARNET is to l of GARNET is to enhance international cooperation, coordination and communicatioenhance international cooperation, coordination and communication through the n through the teleseismic waveform data exchange among regional and national steleseismic waveform data exchange among regional and national seismic eismic networks for selected earthquakes worldwide to study the Earthnetworks for selected earthquakes worldwide to study the Earth’’s deep structure. s deep structure. Last year, however, GARNET has been discontinued with the expectLast year, however, GARNET has been discontinued with the expectations of ations of broadband network to be installed in selected areas around the cbroadband network to be installed in selected areas around the country.ountry.

►► PHIVOLCS Tsunami Detection stations is at its early stage bePHIVOLCS Tsunami Detection stations is at its early stage being financed by the ing financed by the Government of Finland. The project aims to enhance and strengtheGovernment of Finland. The project aims to enhance and strengthen the capability n the capability of selected coastline communities to avert casualties and immediof selected coastline communities to avert casualties and immediately respond to ately respond to threats from farthreats from far--field tsunamis through intensive information campaign focused onfield tsunamis through intensive information campaign focused onan effective warning system developed through collaborative actian effective warning system developed through collaborative activities between vities between local government officials, scientists and primary stakeholders.local government officials, scientists and primary stakeholders.

►► The Metro Manila The Metro Manila Strong Motion Array Strong Motion Array Network (MMSTAR) in Network (MMSTAR) in collaboration with Tokyo collaboration with Tokyo Institute of Technology Institute of Technology (TIT), started in 1998 to (TIT), started in 1998 to provide basic materials provide basic materials used in strong motion used in strong motion prediction for possible prediction for possible future events near Metro future events near Metro Manila. The network Manila. The network consists of 10 Kinemetrics consists of 10 Kinemetrics digital accelerographs and digital accelerographs and are deployed in different are deployed in different subsurface geological subsurface geological conditions in the conditions in the Metropolis. The data are Metropolis. The data are archived and added to the archived and added to the Metro Manila strong Metro Manila strong motion database.motion database.

•• INTERNATIONAL COOPERATIONS (contINTERNATIONAL COOPERATIONS (cont’’d)d)……

K2 Strong Motion Accelerograph

by KINEMETRICS

•• The United Nations Global Program for Integration of Public The United Nations Global Program for Integration of Public Awareness and the Science of Disaster (UNDPAwareness and the Science of Disaster (UNDP--IPASD) donated IPASD) donated CSCAN (Crustal Stress and Community Awareness Network). It is a CSCAN (Crustal Stress and Community Awareness Network). It is a project that aims to involve the community in earthquake detectiproject that aims to involve the community in earthquake detection on and safety. The piezomagnetic sensors installed in 10 stations iand safety. The piezomagnetic sensors installed in 10 stations in n Luzon Island are used to monitor crustal stress changes in the rLuzon Island are used to monitor crustal stress changes in the rock ock that may serve as precursor to an impending large earthquake.that may serve as precursor to an impending large earthquake.

►► The mode of receiving crustal stress data from field stationsThe mode of receiving crustal stress data from field stations are are as follows:as follows:

a.a. data are gathered by trained data are gathered by trained residentresident volunteers.volunteers.b.b. data are sent by fax or email.data are sent by fax or email.c.c. data are processed by both Chinese and Philippine scientists.data are processed by both Chinese and Philippine scientists.

•• Crustal Stress Crustal Stress Sensor & RecorderSensor & Recorder

• FUTURE PLANS

► Among the continuing and projected activities under this program are studies on earthquake source mechanisms, strong ground motions, delineation of seismic/aseismic zones, foreshocks, seismic expectancy and other prediction techniques. This program, along with the Volcano Monitoring and Eruption Prediction Program generates informationneeded for earthquake disaster preparedness planning, vulnerability or risk studies, earthquake disaster mitigation studies, and information campaigns.

► Aside from basic contributions to seismological research in the Pacific region, PHIVOLCS expects to develop and adapt technologies necessary to improve monitoring, seismological research, earthquake prediction and disaster mitigation.

THANK YOU!THANK YOU!

PLATE TECTONICS