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Philippine Institute of Volcanology and Seismology, Powered by Joomla!
Wednesday, 15 February 2017 10:59

PHIVOLCS Quick Response Team (QRT) maps out the ground rupture along the Philippine Fault - Surigao Segment in Poblacion, San Francisco, Surigao del Norte.

Saturday, 11 February 2017 22:22
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What is happening at Surigao del Norte?

At 10:03 PM on 10 February 2017, Friday, a strong earthquake of magnitude 6.7 shook the island of Mindanao. The epicenter is located 16 km offshore northwest of Surigao City, Surigao Strait at a depth of 10 km. The earthquake was generated by the movement of Surigao segment of the Philippine Fault. Small-magnitude earthquakes followed afterwards, and as of 4:00 PM of 11 February 2017, 101 aftershocks have been recorded by the PHIVOLCS seismic monitoring network.

Epicentral mao of the 10 February 2017 M6.7 Surigao del Norte Earthquake

Based on preliminary intensity reports, the strongest ground shaking was felt at PHIVOLCS Earthquake Intensity Scale (PEIS) VII (Destructive) in Surigao City. Furthermore, the municipalities of Pintuyan in Southern Leyte, and San Francisco and Malimono in Surigao del Norte experienced the ground shaking at PEIS VI (Very Strong), while the municipalities of Mainit and Placer in Surigao Del Norte, Libjo and San Jose in Dinagat Island, San Ricardo, Limasawa and San Francisco in Southern Leyte and Manduae City felt the shaking at PEIS V (Strong). This earthquake was felt PEIS IV to I as far as 250 km away (Butuan City, Ormoc City, Tacloban City, Catbalogan City, Bislig City, Cebu City, Cagayan De Oro City, Dumaguete City and Tagbilaran City) from the epicentral area. The strong ground shaking near the epicentral area resulted to damages to some buildings, roads and bridges.

Intensity Map of the 10 February 2017 M6.7 Surigao del Norte EQ

Large earthquakes has affected Surigao del Norte in the past!

On 01 July 1879, a magnitude 7.4 earthquake was generated by the movement of the Surigao segment of the Philippine Fault. This earthquake was considered to be the largest historical earthquake in this area. During this event, strong ground shaking was felt in Surigao del Norte and caused significant damage to churches, buildings and road. A surface rupture, as well as widespread liquefaction and landslides, were also documented.

Why do earthquakes occur in Surigao del Norte?

Eastern Mindanao, including Surigao del Norte, is one of the seismically active areas in the country because of the Philippine Fault and Philippine Trench, which are the main earthquake generators that can affect the area. In addition, there are other local faults which can be sources of small- to large-magnitude earthquakes.

Can these present earthquakes indicate volcanic activity?

No. There are no active volcanoes in the epicentral area.

What can we expect from the current earthquake activity?

The current seismic trend indicates that the magnitude 6.7 earthquake on 10 February 2017 is the main shock, which caused the strong ground shaking. The succeeding small-magnitude earthquakes are the aftershocks. The aftershocks may continue to occur for several days to weeks, some of which may be felt. However, the probability of an earthquake higher than 6.7 magnitude to occur is low.

Aside from strong ground shaking, what other seismic hazards are life-threatening?

Landslides, rock falls, and other types of mass movements may occur in mountainous or hilly areas. Liquefaction, manifested by sand boils or lateral spread may affect low-lying, water-logged, sandy areas at the banks of rivers. Tsunami is not expected from the kind of movement of the Philippine Fault - Surigao segment. The tsunami threat for Surigao del Norte would come from the movement of the Philippine Trench, located east of the province.

What should be done by the affected communities?

People are reminded to be cautious of structures visibly weakened or with signs of damage by the 10 February 2017, as these may be further damaged by aftershocks. In case of houses and other buildings with visible damage, it is best to contact the Municipal/City Engineering Office for advice. Engineers from the local government, other agencies and organizations should inspect buildings and other infrastructures to determine their integrity, and recommend appropriate actions to concerned affected groups or individuals. Slopes should be checked for tension cracks that may have resulted from the strong ground shaking. Tension cracks may make slopes more susceptible to landslides. These areas should be avoided.

The best course of action is preparedness. In case of another felt earthquake, it is recommended that people protect themselves by doing the “duck, cover and hold”. In homes and offices, heavy furniture should be strapped to the walls, and appliances be secured to prevent them from toppling and causing injuries to persons. (check PHIVOLCS Earthquake Preparedness Guide)

What is the role of PHIVOLCS?

PHIVOLCS operates and maintains a network of 92 seismic stations spread across the Philippines. Data from the seismic stations are used to determine the location, magnitude and other characteristics of the earthquakes generated.

The closest seismic stations to Surigao del Norte are the Surigao City (Surigao del Norte) and Bislig (Surigao del Sur) staff-controlled (manned) seismic stations, and the Maasin (Southern Leyte), General Luna (Surigao del Norte) and Butuan City (Agusan del Norte) remote-telemetered seismic stations. (Check the Philippine Seismic Network as of 2016)

Aside from monitoring the occurrences of earthquakes, PHIVOLCS also conducts hazards analyses and assessments, and make this information available to the public. PHIVOLCS works hand-in-hand with other government agencies in mitigating the damaging effects of earthquakes.

Please visit our website at http://www.phivolcs.dost.gov.ph , and our Facebook and Twitter accounts for earthquake bulletins, volcano updates, hazard maps, and other information on earthquakes and volcanoes. Earthquake observations may also be reported to PHIVOLCS at telephone numbers (02) 929-9254 and (02) 426-1468 to 79, local 124 and 125.

as of 11 February 2017


Download the full primer here.

Tectonic geomorphology and paleoseismology of the Surigao segment of the Philippine fault in northeastern Mindanao Island, Philippines
Saturday, 11 February 2017 21:25

The Philippine fault is a major strike-slip fault that traverses the entire Philippine archipelago for > 1250 km and has generated at least 10 surface rupturing earthquakes for the past 200 years. To better understand its characteristics, we have conducted review of historical earthquakes, tectonic geomorphic mapping and paleoseismic trenching along the 100-km-long Surigao segment, the northernmost segment of the Philippine fault on Mindanao Island. We mapped the Surigao fault based on aerial photographs and identification of well-defined geomorphic features in the field. Combining this with historical accounts and paleoseismic trenching, we have identified and mapped the surface rupture of the 1879 Mw 7.4 Surigao earthquake. Paleoseismic trenching conducted at two sites also led us to identify evidence of at least four surface-rupturing earthquakes including the 1879 event during the past 1300 years.

Active tectonics; Philippine fault; Tectonic geomorphology; Paleoseismology; Historical earthquake; 1879 Surigao earthquake



  • Jeffrey S. Perez, , Philippine Institute of Volcanology and Seismology, Department of Science and Technology, Quezon City 1101, Philippines
  • Hiroyuki TsutsumiDepartment of Geophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan


Link to the full paper: http://www.sciencedirect.com/science/article/pii/S0040195117300471

PHIVOLCS Conducts REDAS Training for Baguio City
Wednesday, 08 February 2017 00:00

PHIVOLCS conducted a six-day training entitled "Mainstreaming of Disaster Risk Reduction into the Local Development Planning Process, Contingency Planning, and Emergency Preparedness through the Provision and Use of the REDAS Software" for Baguio City last December 5 - 10, 2016. The training was held at Prime Hotel, Baguio City. The goal of the training was to provide and familiarize the participants with the capability of the REDAS Software, especially the modules which are designed to be used for risk assessment.

There was a total of 38 participants during the training. Thirty (30) of them came from the city offices of Baguio City, 1 from Saint Louis University, 2 from the University of Baguio, 2 from University of the Cordilleras, 2 from BENECO and 1 from NEDA - CAR. The participants were provided with REDAS version 2.9b. A total of 39 REDAS software license keys was issued during the said event.

The first day of the training covered the introduction of PHIVOLCS, installation and orientation on the basic features of REDAS Software and basic map reading. The succeeding days of the training covered lectures ranging from Building Risk Database, Earthquake Risk Assessment, the use of SQLite as a Relational and Spatial Database System, and Seismic Hazard Assessment. The new modules for Severe Wind Risk (SWIFT) and Flood Risk (FLOAT) were also incorporated in the training. In addition, software such as Exposure Database Module (EDM), SQLite and Quantum GIS, and the EDM and MyTracks in Android devices were also installed during the training. The participants were taught how to use the EDM in Android Devices for conducting building survey. Different earthquake risk assessment methodologies and computations were also taught in the training, as well as identifying building earthquake damage levels for conducting earthquake risk assessment.

Speakers and facilitators during the training were Maria Leonila P. Bautista, Angelito G. Lanuza, Rhommel N. Grutas, Robjunelieaaa Lim, Emmanuelle Mitiam, Mary Ann T. Montion, Anne Lorraine T. Delos Santos, Ruffy R. Villanueva, Dave Andrei V. Rivera, Greggue Ann Lyza T. Castro, Hilario Esperanza (PAGASA), Clint Drexel M. Ongue, and Joana C. Umbaña.

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