At 14:11 PST (06:11 UTC) on December 15, 2019, the province of

Davao del Sur Davao del Sur ( ceb, Habagatang Dabaw; ), officially the Province of Davao del Sur, is a province in the Philippines located in the Davao Region in Mindanao. Its capital is Digos City. Davao City is the largest city in terms of area and populat ...

on the island of

Mindanao Mindanao ( ) ( Jawi: مينداناو) is the second-largest island in the Philippines, after Luzon, and seventh-most populous island in the world. Located in the southern region of the archipelago, the island is part of an island group of ...

in the

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

was struck by an

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

measuring 6.8 . It had a maximum perceived intensity of VII (''Very strong'') on the

Modified Mercalli Intensity Scale The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

. At least 13 people were killed and another 210 injured.

Tectonic setting

Mindanao lies across the complex

convergent boundary A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more Plate tectonics, lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can ...

between the

Sunda Plate The Sunda Plate is a minor tectonic plate straddling the Equator in the Eastern Hemisphere on which the majority of Southeast Asia is located. The Sunda Plate was formerly considered a part of the Eurasian Plate, but the GPS measurements have ...

and the

Philippine Sea Plate The Philippine Sea Plate or the Philippine Plate is a tectonic plate comprising oceanic lithosphere that lies beneath the Philippine Sea, to the east of the Philippines. Most segments of the Philippines, including northern Luzon, are part of ...

. Part of the oblique convergence between these plates is taken up by

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

along the

Cotabato Trench The Cotabato Trench is an oceanic trench in the Pacific Ocean, off the southwestern coast of Mindanao in the Philippines. Along this trench the oceanic crust of the Sunda Plate beneath the Celebes Sea is being subducted beneath the Philippines ...

. The

strike-slip In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

component of the convergence is accommodated partly by the

Philippine Fault System The Philippine Fault System is a major inter-related system of geological faults throughout the whole of the Philippine Archipelago, primarily caused by tectonic forces compressing the Philippines into what geophysicists call the Philippine Mobil ...

and partly by the Cotabato Fault System, a network of mainly NW-SE trending sinistral (left-lateral) strike-slip faults that form the boundary between the Cotabato Arc and the Central Mindanao Volcanic Belt. In the area of the December 2019 earthquake, the individual faults include the NW-SE trending Makilala–Malungon Fault, Tangbulan Fault and the Central Digos Fault.

Earthquake

The earthquake was recorded as 6.8 by ANSS and 6.9 by

PHIVOLCS The Philippine Institute of Volcanology and Seismology (PHIVOLCS, ; tl, Surian ng Pilipinas sa Bulkanolohiya at Sismolohiya) is a Philippine national institution dedicated to provide information on the activities of volcanoes, earthquakes, and ...

. The maximum felt intensity was assigned as VII MMI on the ANSS ShakeMap and VII

PEIS The PHIVOLCS Earthquake Intensity Scale (PEIS) is a seismic scale used and developed by the Philippine Institute of Volcanology and Seismology (PHIVOLCS) to measure the intensity of earthquakes An earthquake (also known as a quake, tr ...

in the PHIVOLCS summary for this event. The

focal mechanism The focal mechanism of an earthquake describes the deformation in the source region that generates the seismic waves. In the case of a fault-related event it refers to the orientation of the fault plane that slipped and the slip vector and is ...

indicates

strike-slip faulting In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

with either sinistral movement on a NW-SE trending fault or dextral movement on a SW-NE trending fault, but the distribution of the aftershocks are consistent with the sinistral fault plane. The earthquake may be the result of movement on the Tangbulan Fault, according to PHIVOLCS. There were a series of large

aftershock In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousand ...

s, including nine of M ≥ 5.0 in the first 48 hours after the mainshock, with the largest being an 5.7 event about an hour afterwards, which had a maximum felt intensity of VII (MMI). This event followed on from a series of earthquakes that struck Mindanao during October that year. The sequence of three M>6 events affected that area to the northwest of the December earthquake. The December 15 event is likely to be related to the earlier sequence, possibly by the effects of stress transfer.

Damage and casualties

The greatest damage from the earthquake was in the area around the

epicenter The epicenter, epicentre () or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates. Surface damage Before the instrumental pe ...

, in the towns of Matanao,

Magsaysay Ramon del Fierro Magsaysay Sr. (August 31, 1907 – March 17, 1957) was a Filipino statesman who served as the seventh president of the Philippines, from December 30, 1953, until his death in an aircraft disaster on March 17, 1957. An automo ...

, Hagonoy and

Padada Padada, officially the Municipality of Padada ( ceb, Lungsod sa Padada; tl, Bayan ng Padada), is a 3rd class municipality in the province of Davao del Sur, Philippines. According to the 2020 census, it has a population of 29,878 people. Its bou ...

. Significant damage was reported in 207 out of 232 barangays in Davao del Sur, five in

Sarangani Sarangani, officially the Province of Sarangani ( ceb, Lalawigan sa Sarangani; hil, Kapuoran sang Sarangani; Maguindanaon: ''Dairat nu Sarangani'', Jawi: دايرت نو سارڠني; fil, Lalawigan ng Sarangani), is a province in the Philipp ...

, three in

Sultan Kudarat Sultan Kudarat, officially the Province of Sultan Kudarat ( hil, Kapuoran sang Sultan Kudarat; Maguindanaon: ''Dairat nu Sultan Kudarat'', Jawi: دايرت نو سلطان كودرت; ceb, Lalawigan sa Sultan Kudarat; tl, Lalawigan ng Sul ...

and North Cotabato, respectively. This earthquake added to the damage that much of the affected area suffered during the Cotabato earthquakes in October. At least one road was declared impassable in the Matanao area, a hospital was destroyed in Hagonoy and there was significant damage to a police station and fire station in Padada. A total of 5,973 houses were destroyed in Davao del Sur, with 31,832 suffering some damage and a further 32 in

North Cotabato Cotabato or North Cotabato ( hil, Aminhan Cotabato; ceb, Amihanang Cotabato; Maguindanao language, Maguindanaon: ''Pangutaran Kutawatu'', Jawi alphabet, Jawi: ڤڠوترن كوتاواتو; fil, Hilagang Cotabato), officially the Province of Co ...

. Three hundred and ninety-seven schools and 62 health facilities were damaged in Davao del Sur,

and North Cotabato. A six-year-old child was crushed by a wall in the

barangay A barangay (; abbreviated as Brgy. or Bgy.), historically referred to as barrio (abbreviated as Bo.), is the smallest administrative division in the Philippines and is the native Filipino term for a village, district, or ward. In metropolitan ...

of Asinan in Matanao. Three others were killed and several others were trapped in Padada when a supermarket collapsed. As of December 23, at least 13 people had been killed, one remained missing and a total of 210 people were reported injured in the quake.

Aftermath

As of December 29, 40,424 people from 10,505 families were reported to be sheltering in a total of 102 evacuation centers after the earthquake, with a further 100,427 people (23,321 families) being assisted by friends and family.

References

External links