Philippine Standard Time
 

Update as of 18 November 2023

 

What is happening in Sarangani, Davao Occidental and vicinity?

 

At 4:14 PM Philippine Standard Time (PST) on 17 November 2023 (Friday), a strong earthquake with magnitude (MW) 6.8 shook the Municipality of Sarangani, Davao Occidental, and a large portion of Mindanao. The earthquake has an epicenter located 28 kilometers southwest of Sarangani, Davao Occidental, and has an estimated depth of 63 kilometers (Figure 1). The earthquake was likely generated by the Cotabato Trench. As of 8:00 AM PST on 18 November 2023, the DOST-PHIVOLCS Philippine Seismic Network (PSN) has recorded a total of 58 aftershocks ranging from M1.4 to M3.9.

Using the PHIVOLCS Earthquake Intensity Scale (PEIS), the highest reported intensity is PEIS VII (Destructive) which was felt in Glan, Sarangani based on the DOST-PHIVOLCS Earthquake Information 4 (Annex 1). At PEIS VII, many people are frightened and may run outdoors. Heavy objects and furniture overturn or topple. Big church bells may ring. Old or poorly-built structures suffer considerable damage. Some well-built structures are slightly damaged. Some cracks may appear on dikes, fish ponds, road surface, or concrete hollow block walls. Limited liquefaction, lateral spreading and landslides are observed. Trees are shaken strongly.

davao occi 18Nov2023
Have strong to great earthquakes affected Sarangani, Davao Occidental, and its vicinity in the past?

Yes. At least six significant earthquakes with magnitudes ranging from M5.7 to M8.0 affected Sarangani, Davao Occidental, and nearby provinces between 1917 and 2017 based on the historical records (SEASEE, 1987) and DOST-PHIVOLCS Earthquake Catalog. The last damaging earthquake in Sarangani, Davao Occidental and its vicinity was a M7.2 event that occurred on 29 April 2017.

Why do earthquakes occur in the vicinity of Sarangani, Davao Occidental?

Sarangani, Davao Occidental and neighboring provinces experience earthquakes as they are situated in one of the seismically active regions in the country. The presence of offshore active faults and trenches, including an unnamed offshore fault east of Davao Occidental and the Cotabato Trench, contributes to seismic activity. Additionally, there are local faults in proximity, some potentially concealed by recent deposits capable of generating earthquakes ranging from minor to strong magnitudes.

What can we expect from the current earthquake activity?

We can expect aftershocks in the epicentral area. These aftershocks could persist for several days to weeks, and some may be felt in nearby provinces.

 

Minor earthquakes: M3 to 3.9; Light earthquakes: M4 to 4.9; Moderate earthquakes: M5 to 5.9; Strong earthquakes: M6 to 6.9; Major earthquakes: M7 to 7.9; Great earthquakes: M8.0 and above

 

Aside from strong ground shaking, what other seismic hazards may be expected?

Earthquake-induced landslides, rock falls, and other types of mass movement may occur on sloping terrains, specifically in mountainous or hilly areas. Liquefaction, manifested by subsidence, ground fissures, sand boils, and/or lateral spreads may affect low-lying, water-saturated, and sandy areas near water bodies. Active river channels and coastal areas may be vulnerable to inundation of seawater due to the combination of liquefaction-induced subsidence, and changes in sea level due to high tide.

Can this recent earthquake event trigger a destructive tsunami?

No. While the recent earthquake itself, due to its depth, is less likely to directly generate a destructive tsunami. However, submarine landslides triggered by the strong shaking could lead to the displacement of water, causing localized tsunamis that may not be as extensive but can still pose a threat to nearby coastal areas. In case of another strong shaking, coastal communities should be watchful and stay away from beaches and not go to the coast.

Can this earthquake indicate volcanic activity?

No. Although the nearest active volcano in Sarangani is the Parker Volcano, the MW 6.8 earthquake was determined to be tectonic in origin. However, as part of PHIVOLCS-DOST monitoring procedures for moderate to major earthquakes occurring near active volcanoes, the Institute will closely monitor earthquake events concerning any activity that may be associated with the Parker Volcano.

What should be done by the affected communities?

Communities should prepare for aftershocks. In case of another strongly felt earthquake, it is recommended that people protect themselves by doing the “drop, cover, and hold.” In homes and offices, heavy furniture and appliances should be strapped to the walls, and hanging objects securely fastened to prevent these from causing injuries.

People should be cautious of structures visibly weakened or having signs of damage caused by the MW 6.8 earthquake event, as these may further be damaged by succeeding earthquakes and injure building occupants. It is best to contact the concerned Municipal/City Engineering Office for inspection and advice. Civil engineers from the local government and other organizations are strongly enjoined to inspect buildings and infrastructure to determine their structural integrity and recommend appropriate actions. Structurally compromised buildings should not be reoccupied unless certified safe by structural engineers. Slopes should be checked for tension/incipient cracks that may have resulted from the strong ground shaking.

Tension cracks may render slopes more susceptible to landslides, especially during heavy rainfall or aftershocks. Areas that may be affected by impending landslides should be avoided.

During earthquake events, rumors that may cause panic are easily spread. Please avoid sharing messages from unconfirmed and unreliable sources, and only rely on information from DOST-PHIVOLCS and respective Disaster Risk Reduction and Management Offices (DRRMOs).

What is the role of DOST-PHIVOLCS?

DOST-PHIVOLCS conducts seismic monitoring and provides earthquake information. In addition, DOST-PHIVOLCS also operates and maintains a network of 123 seismic stations spread across the Philippines. The closest seismic stations to Sarangani are the staff-controlled seismic stations in General Santos City, Davao City, Kidapawan City, and Cotabato City, and remote-telemetered seismic stations in Don Marcelino in Davao del Sur, Bagumbayan in Sultan Kudarat, Pikit in Cotabato, and Mati City. These stations are augmented by the Matutum and Parker Volcano Observatory.

DOST-PHIVOLCS will deploy a Quick Response Team (QRT) to the provinces of Sarangani, Davao Occidental, and South Cotabato. The DOST-PHIVOLCS QRT aims to assess impacts and hazards and conduct information dissemination campaigns to allay the fears of the public. Furthermore, DOST-PHIVOLCS works hand-in-hand with other government agencies in mitigating the damaging effects of the earthquake events in these provinces.

Please visit our website at www.phivolcs.dost.gov.ph, and our Facebook (/PHIVOLCS) and X (@phivolcs_dost) accounts for earthquake information, volcano updates, hazard maps, and other information on earthquakes and volcanoes. Earthquake observations may also be reported to DOST-PHIVOLCS at telephone numbers (02) 8929-9254 and (02) 8426-1468 to 79, local 307 and 308, or through our official social media accounts.

 

 

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