It shocked the multiple cities, towns, and provinces in the island of Mindanao and even in some parts of Visayas.
At 7:37 am on Monday, June 8, a major Magnitude 7.8 earthquake jolted the province of Sarangani and its surrounding areas in Mindanao.
According to the Philippine Institute of Volcanology and Seismology (PHIVOLCS), the earthquake’s epicenter was located offshore, 32 kilometers west of Maasim, Sarangani, and an estimated depth of 33 kilometers.
“Based on the location of the earthquake, focal mechanism, and aftershock distribution, the earthquake may be attributed to subduction along the Cotabato Trench,” the state seismology bureau added in its primer released at noon on June 8.
As of 11:00 am, the DOST-PHIVOLCS Philippine Seismic Network (PSN) has also recorded a total of 138 aftershocks ranging from Magnitude 1.3 to 6.7.
“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,” further noted PHIVOLCS.
INTENSITIES
Meanwhile, citing data from the PHIVOLCS Earthquake Intensity Scale (PEIS), the highest reported intensity is PEIS VII (Destructive) that was felt in General Santos City, with the ground shaking felt as far as Abuyog and Dulag in Leyte at PEIS II (Slightly felt).
- Reported Intensities
- Intensity VII – CITY OF GENERAL SANTOS
- Intensity VI – Palimbang, and Senator Ninoy Aquino, SULTAN KUDARAT
- Intensity V – CITY OF DAVAO; City of Kidapawan, and Carmen, COTABATO; Bagumbayan, Kalamansig, and President Quirino, SULTAN KUDARAT; Sibuco, and Siocon, ZAMBOANGA DEL NORTE
- Intensity IV – City of Mati, DAVAO ORIENTAL; Buug, ZAMBOANGA SIBUGAY; Caraga, Manay, and Tarragona, DAVAO ORIENTAL
- Intensity III – CITY OF BUTUAN; Mainit, SURIGAO DEL NORTE; City of Dapitan, ZAMBOANGA DEL NORTE; Kumalarang, Vincenzo Sagun, ZAMBOANGA DEL SUR
- Intensity II – City of Dipolog, Labason, Liloy, President Manuel A. Roxas, and Salug ZAMBOANGA DEL NORTE; Alicia, Ipil, Mabuhay, Olutanga, and Siay, ZAMBOANGA SIBUGAY; Molave, ZAMBOANGA DEL SUR; Abuyog, and Dulag, LEYTE; San Francisco, SOUTHERN LEYTE
- Instrumental intensities
- Intensity VII – City of Koronadal, SARANGANI; Santa Maria, DAVAO OCCIDENTAL
- Intensity V – CITY OF DAVAO
- Intensity III – Abuyog, LEYTE
- Intensity II – San Francisco, SOUTHERN LEYTE; Dulag, LEYTE
TSUNAMI
Meanwhile, due to its powerful strength, the earthquake generated tsunami waves, which were recorded along the coasts of Kiamba and Maasim, Sarangani, and Kalamansig, Sultan Kudarat.
Based on data from the DOST-PHIVOLCS Sea Level Monitoring Stations, the wave reached a height of approximately 1 meter.
Meanwhile, tsunami waves of less than 1 meter in height were also recorded in Mati City and Zamboanga City.
The said tsunami warning was also issued in surrounding countries, such as Malaysia, Indonesia, and Papua New Guinea.
HAZARDS
Meanwhile, PHIVOLCS also warned of earthquake-induced landslides, rock falls, and other types of mass movement may have occurred in mountainous or hilly areas.
It also noted the possibility of liquefaction, manifested by subsidence, ground fissures, sand boils, and/or lateral spreads, may have affected 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.
Furthermore, sinkholes may appear in areas with limestone bedrock. In case of another strong earthquake, these hazards may occur.
HISTORICAL CONTEXT, VOLCANOES NOT CAUSE OF EARTHQUAKE
Meanwhile, at least seven significant earthquakes with magnitudes ranging from Magnitude 5.7 to Magnitude 8.0 affected Sarangani and nearby provinces between 1917 and 2023, according to the DOST-PHIVOLCS Earthquake Catalog.
The last damaging earthquake in Sarangani and its vicinity was a Magnitude 6.8 event that occurred on 17 November 2023.
PHIVOLCS also explained, “Sarangani and neighboring provinces experience earthquakes as they are situated in one of the seismically active regions in the country. The coast of Sarangani faces the Cotabato Trench, a major earthquake-generating structure.”
It also mentioned the existence of local faults in proximity, which it told some may have been potentially concealed by recent deposits.
As regards to volcanic correlation, the nearest active volcanoes to Sarangani are the Matutum and Parker Volcanoes, with the PHIVOLCS clearly noting that the 7.8 earthquake on Monday is tectonic in origin.
“Nevertheless, in line with standard monitoring protocols for moderate to great earthquakes occurring near active volcanoes, the Institute will continue to closely monitor the area for any volcanic activity that may be affected by the event,” the bureau added.
PHIVOLCS will also deploy a Quick Response Team (QRT) to Sarangani Province and vicinity to conduct geologic impacts assessment and information dissemination campaigns to calm the public.
PBBM ISSUES STATEMENT
Following the powerful earthquake, President Ferdinand Marcos, Jr. issued a statement to disclose the government’s response to the emergency situation.
“I have directed all relevant government agencies to act immediately,” the Chief Executive told.
The Office of Civil Defense and the National Disaster Risk Reduction and Management Council (NDRRMC) are already coordinating disaster response and monitoring across all affected areas.
As for the Department of Social Welfare and Development (DSWD), it has been directed to pre-position relief goods and ensure that evacuation centers are ready and operational.
Meanwhile, the Department of Public Works and Highways (DPWH) is “on standby” to assess damage to roads, bridges, and critical infrastructure, and to clear routes needed for rescue and relief operations.
“I am also ordering the suspension of classes in all levels across affected areas in Mindanao until further notice. The safety of our children comes first. DepEd (Department of Education) will coordinate with local government units on this,” furthered PBBM.
“The national government is moving and we will not leave Mindanao behind,” Marcos added. “I am in constant communication with our regional offices and local chief executives on the ground.”