LIST: Killer earthquakes in the Philippines
[This report was first published July 27, 2022. It was updated in the wake of the magnitude-7.8 earthquake in Mindanao on Monday, June 8.]
READ: Mindanao earthquake: 19 killed, hundreds hurt, buildings toppled
MANILA, Philippines — A magnitude-7.8 earthquake struck off Sarangani on Monday, June 8, resulting in structural damage, service disruptions and class suspensions on the first day of the school year.
The Philippine Institute of Volcanology and Seismology (Phivolcs) said the earthquake struck at 7:37 a.m., with its epicenter located 32 kilometers south 4 degrees west of Maasim, Sarangani, at a depth of 33 kilometers.
Phivolcs reported Intensity VII in General Santos City; Intensity VI in Palimbang and Senator Ninoy Aquino, Sultan Kudarat; and Intensity V in Davao City, Kidapawan City, Carmen in Cotabato, Bagumbayan, Kalamansig and President Quirino in Sultan Kudarat, as well as Sibuco and Siocon in Zamboanga del Norte.
Instrumental Intensity VIII was recorded in Malapatan, Sarangani. Instrumental Intensity VII was recorded in Koronadal City, South Cotabato, and Santa Maria, Davao Occidental.
Ring of Fire
As it is located in the Pacific Ring of Fire, the Philippines is at risk from earthquakes, with Phivolcs saying 100 to 150 earthquakes hit the country every year.
Last year on Sept. 30, a magnitude-6.9 earthquake hit Cebu, leaving 69 people dead, 147 injured and P2 billion worth of damage.
Rafael Alejandro IV, assistant secretary of the Office of Civil Defense (OCD), said most of the deaths were in Bogo City — the epicenter of the earthquake — at 30, followed by 22 in San Remigio; 10 in Medellin; five in Tabogon; and one each in Sogod and Tabuelan.
READ: Cebu earthquake death toll now at 69 – OCD
The province is already in a state of calamity, with officials saying they do not know the extent of the damage because many areas, particularly remote villages, have yet to be accessed.
The magnitude-6.9 earthquake struck at 9:59 p.m., with the epicenter located 21 kilometers northeast of Bogo City at a shallow depth of five kilometers. It was felt as far as Camarines Sur in Luzon and Davao del Sur in Mindanao.
READ: Cebu quake aftershocks may persist for weeks – Phivolcs
An earthquake, Phivolcs said, is “a weak to violent shaking of the ground produced by sudden movement of rock materials below the earth’s surface.” It said earthquakes originate in the tectonic plate boundary.
There are two ways to measure the strength of an earthquake: magnitude and intensity. Magnitude is proportional to the energy released by an earthquake, while intensity is generally higher near the epicenter.
In 2022, a magnitude-7.0 earthquake (earlier measured at 7.3) hit Tayum, Abra, prompting President Ferdinand Marcos Jr. to order the immediate deployment of rescue and relief teams to Northern Luzon.
READ: Magnitude 7 earthquake jolts Abra, other parts of Luzon
The earthquake, which was strongly felt in Luzon, killed 11 people and left P1.4 billion worth of damage.
READ: 1 dead as building collapses in Benguet town due to quake
Heritage structures in Vigan City, Ilocos Sur were also reported damaged by the earthquake, which struck at 8:43 a.m. and was felt at different intensity levels mainly in Northern Luzon and as far as Metro Manila.
READ: Heritage structures, churches damaged by 7.3 quake
RELATED STORY: Earthquake damages structures, bridges in Abra town — initial reports
INQUIRER.net lists some of the killer earthquakes that hit the Philippines, which is surrounded by active faults, including the West Valley Fault, which is 100 kilometers long.
INQUIRER.net lists some of the killer earthquakes that hit the Philippines, which is surrounded by active faults, including the West Valley Fault, which is 100 kilometers long.
GRAPHIC: Ed Lustan / INQUIRER.net
Casiguran earthquake
A magnitude-7.3 earthquake with an intensity of 8 struck Casiguran, Aurora at 4:19 a.m. on Aug. 2, 1968 — the most severe and destructive experienced in the Philippines at the time — leaving “several millions of pesos worth of damage.”
Phivolcs said 270 people were killed and 261 were injured as a result of the earthquake. A six-story building in Binondo, Manila, collapsed instantly while some buildings near Binondo and Escolta in Manila sustained varying levels of structural damage.
Phivolcs said: “The cost of property damage was several million dollars. Extensive landslides and large fissures were observed in the mountainous part of the epicentral area. Tsunami was also observed and recorded as far as observations in tide gauge stations in Japan.”
Moro Gulf earthquake
Phivolcs said that a few minutes after the stroke of midnight on Aug. 17, 1976, a magnitude-8.1 earthquake hit the island of Mindanao, triggering a tsunami that devastated more than 700 kilometers of coastline bordering Moro Gulf in the Celebes Sea. Damage was estimated at P6.7 billion.
It was an earthquake that resulted in massive destruction of properties and great loss of lives — 8,000. Phivolcs said the tsunami was responsible for 85% of deaths, 65% of the injuries and 95% of those missing.
Phivolcs said: “After the sea spent its fury and rolled back to its natural flow, thousands of people were left dead, others homeless or missing and millions of pesos lost with the damages of properties.”
Some of the structures damaged by the earthquake were the Notre Dame University, Dawns Hotel, Imperial Hotel, Melbourne Hotel, New Society Hotel, Cotabato Cinema and the Immaculate Conception Church.
Laoag earthquake
On Aug. 17, 1983, at 8:18 p.m., a magnitude-6.5 earthquake with an intensity of 7 hit Ilocos Norte. The tremor was perceptible over a distance of 400 kilometers from the epicenter.
Phivolcs said it was the most severe earthquake in northwestern Luzon in 52 years and probably the second-strongest earthquake to hit Laoag City and its immediate vicinity.
The earthquake destroyed buildings in the province and left 16 people dead and 47 wounded. The most heavily damaged structures in Laoag City were those near the Laoag River flood plain and along reclaimed stream channels.
Phivolcs said: “Several earthquake-induced landslides were observed in places where the slopes along road cuts were steep to very steep. This condition had been aggravated by prolonged rainy days, absence of vegetation to hold the soil, and moderately weathered rocks.”
Panay earthquake
Panay Island was hit by a magnitude-7.1 earthquake on June 14, 1990, leaving eight people dead and 41 wounded. Its epicenter was tagged in the vicinity of Culasi, Antique.
The earthquake’s depth, Phivolcs said, was computed to be 15 kilometers and was generated by fault movement in the collisional zone off western Panay Island. An intensity of 7 was felt in Culasi, Antique, and Libacao, Aklan.
Because of the earthquake, 15% of residential houses collapsed while the rest were damaged. Several commercial buildings, a school, a church and bridges collapsed. Damage was estimated at P30 million.
Luzon earthquake
The International Code Council said the magnitude-7.8 earthquake that struck Luzon on July 16, 1990, wreaked havoc across a sizable portion of the island, the country’s largest, with Baguio City suffering the most devastating effects.
The epicenter of the earthquake, which struck at 4:26 p.m., was located in Rizal, Nueva Ecija. The shaking went on for nearly a full minute, and collapsing buildings were the main cause of damage and death.
The earthquake resulted in a number of collapsed buildings, left an estimated $369 million worth of damage and 2,412 people dead. It produced a 125-kilometer-long ground rupture that stretches from Dingalan, Aurora, to Kayapa, Nueva Vizcaya.
Mindoro earthquake
According to the International Tsunami Information Center, a magnitude-7.1 earthquake hit Mindoro province on Nov. 15, 1994, leaving damage worth P67.2 million. The earthquake generated a local destructive tsunami.
In Oriental Mindoro, the combined effects of the earthquake and the tsunami killed 78 people, injured 430, damaged or destroyed 7,566 houses in 13 out of 15 municipalities, damaged roads, destroyed or damaged 24 bridges and sank numerous fishing boats.
It said there was no time to issue a warning. About five minutes after the tremor, tsunami waves struck along a 40-kilometer stretch of the northern and eastern shoreline of Mindoro island, from Puerto Galera up to Pinamalayan.
Negros Oriental earthquake
A magnitude-6.7 earthquake shook the provinces of Negros and Cebu, and nearby islands of Western Visayas, at 11:49 a.m. on Feb. 6, 2012.
The earthquake was generated by a thrust fault movement with the epicenter located in Tayasan, Negros Oriental. An intensity of 8 was felt in Tayasan, Vallehermoso, Jimalalud, La Libertad and Guihulngan, Negros Oriental.
The estimated cost of damage to infrastructure was P383 million. The earthquake left 51 dead and 112 injured, while 62 were reported missing from the landslide in Solongon, La Libertad, and Planas, Guihulngan.
Tsunami waves as high as five meters also struck Barangays Martilo, Pisong and Magtalisay in La Libertad, Negros Oriental. Coastal areas of Negros Oriental from San Jose to Vallehermoso, and Cebu from Badian to Barili, were also affected by the tsunami.
Bohol earthquake
It was on Oct. 15, 2013, when a magnitude-7.2 earthquake struck the Visayas. The epicenter was located in Bohol in Central Visayas, but the shaking was felt as far as Southern Mindanao.
The earthquake affected more than 1.2 million people. A total of 222 people died, 976 were injured and eight were missing. Over 79,000 structures, including homes, roads, churches, schools and public buildings, were damaged, according to a World Health Organization report. At least 14,500 of these structures were destroyed, the WHO report said.
The earthquake, which hit a month before Typhoon Yolanda (Haiyan) struck the Visayas, left damage worth P2.25 billion.
Central Luzon earthquake
Zambales, Pampanga and nearby provinces were hit by a magnitude-6.1 earthquake at 5:11 p.m. on April 22, 2019, leaving damage to infrastructure worth P539 million.
The epicenter was located 18 kilometers east of Castillejos, Zambales, in a mountainous area, at a depth of 10 kilometers. Small-magnitude earthquakes followed afterward, and as of 8 a.m., April 23, 2019, 421 aftershocks had been recorded.
The earthquake left 18 people dead and 256 injured, while three people went missing.
Davao del Sur earthquake
At 2:11 p.m. on Dec. 15, 2019, a magnitude-6.9 earthquake shook Davao del Sur and its vicinity. The epicenter was located nine kilometers northwest of Matanao, Davao del Sur, at a depth of three kilometers.
The earthquake followed the quake events on July 9, 2019, and Oct. 16, 2019. After this, a total of 530 small to moderate earthquakes have been recorded.
RELATED STORY: Work, classes suspended in Abra, Baguio due to quake
The National Disaster Risk Reduction and Management Council said the earthquake left nine dead and injured hundreds of people. Damage was estimated at P4.55 million. /dm
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