List of earthquakes in the Philippines
The Philippines lies within the zone of complex interaction between several tectonic plates, involving multiple subduction zones and one large zone of strike-slip, all of which are associated with major earthquakes. Many intraplate earthquakes of smaller magnitude also occur very regularly due to the interaction between the major tectonic plates in the region. The largest historical earthquake in the Philippines was the 1918 Celebes Sea earthquake with Mw8.3.
Largest
Mw 8.0 1976 Moro Gulf earthquake 5,000–8,000 killed
Seismicity[edit]
Subduction zones[edit]
The subduction zones that surround most of the archipelago are the source of many of the larger earthquakes that strike the Philippines. This includes both faulting along the plate interfaces and within the subducting slabs. For the Philippine Trench, examples of those on the plate interface are the 1988 Mw 7.3 and the 2023 M7.6 events. The 1975 Mw 7.6 earthquake was caused by intra-slab normal faulting, while the 2012 M7.6 was a result of thrust faulting within the descending slab.[3]
The relatively young Cotabato Trench subduction zone has been associated with several large megathrust earthquakes, including the 1918 Celebes Sea earthquake (M8.3), the 1976 Moro Gulf earthquake (M8.0) and the 2002 Mindanao earthquake (M7.5).[4][5]
Strike-slip zones[edit]
The longest and most seismically active of the strike-slip structures is the 1200 km long Philippine Fault Zone.[6] It carries the left lateral component of the oblique convergence at the Philippine Trench, with a current estimated slip-rate of 35 ± 4 mm per year on Leyte, reducing northwards to about 20 mm per year on Luzon. On Luzon, the fault zone splays out into a number of different faults, including the Digdig Fault. One of the largest historical earthquake on the fault zone was the 1990 Luzon Ms 7.8 event that left nearly 2,000 people dead or missing. The same part of the fault zone is thought to have ruptured in the 1645 Luzon earthquake.[7] Further south the fault ruptured during the 1973 Ragay Gulf earthquake.
In central Mindanao, the Cotabato fault system consists of a mixture of NW-SE trending left lateral and SW-NE trending right lateral strike-slip faults. Four of these ruptured in the 2019 Cotabato and Davao del Sur earthquakes, each generating events with magnitudes of 6.4 or greater.[8]
Seismic hazard[edit]
Given the presence of major fault zones throughout the archipelago, any part of the Philippines may be affected by earthquakes, apart from parts of Palawan, where the seismic hazard risk is comparatively low. The greatest shaking hazard comes from shallow crustal faulting close to the Manila, Davao and Cebu metropolitan areas. Active reverse faults have >20 km wide zones of peak ground acceleration (PGA) >0.6g (acceleration due to gravity) for a 10% probability of exceedance (PoE) in a 50 year period, while active strike-slip faults have narrower zones centered around the fault traces at a similar level. All areas close to active subduction zones show increased hazard.[9]
In Metro Manila the estimated hazard has a mean PGA of 0.32 g for a PoE of 10% in 50 years. The main hazard comes from shallow fault sources, such as the Marikina Valley Fault System, but there is an important contribution to the overall hazard from the Manila subduction zone to the west and the potential for strong shaking from earthquakes originating the Philippines Trench to the east. In Metro Cebu, the mean PGA is also 0.32 g for the same PoE and period. The hazard is dominated by shallow crustal fault zones from this area of ongoing compressional tectonics. Using the same parameters Metro Davao has the higher value of 0.45 g. The metropolitan area sits close to shallow faults of left lateral strike-slip and oblique reverse type, and these generate the greatest hazard, although a significant contribution comes from sources in the Halmahera and Philippine subduction zones.[9]