Saturday, 16 June 2012

The Philippines Earthquake History

One of the most frightening and destructive phenomena of nature is a severe earthquake and its terrible after effects. An earthquake is the sudden, rapid shaking of the earth, caused by the breaking and shifting of subterranean rock as it releases strain that has accumulated over a long time.

For hundreds of millions of years, the forces of plate tectonics have shaped the earth, as the huge plates that form the earth’s surface slowly move over, under and past each other. Sometimes, the movement is gradual. At other times, the plates are locked together, unable to release accumulated energy.

When the accumulated energy grows strong enough, the plates break free. If the earthquake occurs in a populated area, it may cause many deaths and injuries and extensive property damage.

Earthquakes Volcanic in origin
Earthquakes related to volcanic activity may produce hazards which include ground cracks, ground deformation, and damage to man made structures. People living near an erupting volcano are very aware of volcanic earthquakes. Their houses will shake and windows rattle from the numerous earthquakes that occur each day before and during a volcanic eruption. Residents in Pompeii felt earthquakes daily before Vesuvius erupted in A.D. 79 but continued to go about their daily routines. When Mount Pinatubo  erupted in 1991, nerves were rattled as much as windows by volcanic earthquakes.

Earthquakes exhibiting volcanic tremor warn of an impending eruption so that people can be evacuated to areas of safety. The volcanic tremor signal has been used successfully to predict the 1980 eruptions Mount St. Helens and the 1991 eruption of Pinatubo. To prevent damage from being done, structures should be built according to earthquake standards, building foundations should be constructed on firm ground and not unconsolidated material which may amplify earthquake intensity, and buildings should be constructed on stable slopes in areas of low hazard potential. There are two general categories of earthquakes that can occur at a volcano: 1. volcano-tectonic earthquakes and 2. long period earthquakes. 

Volcano-Tectonic Earthquakes:
Earthquakes produced by stress changes in solid rock due to the injection or withdrawal of magma (molton rock). These earthquakes can cause land to subside and can produce large ground cracks. These earthquakes can occur as rock is moving to fill in spaces where magma is no longer present. Volcano-tectonic earthquakes don't indicate that the volcano will be erupting but can occur at anytime.

Long period earthquakes:
Are produced by the injection of magma into surrounding rock these earthquakes are a result of pressure changes during the unsteady transport of the magma. When magma injection is sustained a lot of earthquakes are produced. This type of activity indicates that a volcano is about to erupt. Scientists use seismographs to record the signal from these earthquakes. This signal is known as volcanic tremor.

Earthquakes  Tectonic in origin
Tectonic earthquakes occur anywhere in the earth where there is sufficient stored elastic strain energy to drive fracture propagation along a fault plane. The sides of a fault move past each other smoothly and aseismically only if there are no irregularities or asperities along the fault surface that increase the frictional resistance. Most fault surfaces do have such asperities and this leads to a form of stick-slip behaviour. Once the fault has locked, continued relative motion between the plates leads to increasing stress and therefore, stored strain energy in the volume around the fault surface. This continues until the stress has risen sufficiently to break through the asperity, suddenly allowing sliding over the locked portion of the fault, releasing the stored energy. This energy is released as a combination of radiated elastic strain seismic waves, frictional heating of the fault surface, and cracking of the rock, thus causing an earthquake. This process of gradual build-up of strain and stress punctuated by occasional sudden earthquake failure is referred to as the elastic-rebound theory. It is estimated that only 10 percent or less of an earthquake's total energy is radiated as seismic energy. Most of the earthquake's energy is used to power the earthquake fracture growth or is converted into heat generated by friction. Therefore, earthquakes lower the Earth's available elastic potential energy and raise its temperature, though these changes are negligible compared to the conductive and convective flow of heat out from the Earth's deep interior.

What is an epicenter ?
The epicenter is  the point where an earthquake or underground explosion originates. The word derives from the New Latin noun epicentrum, the latinisation of the ancient Greek adjective epikentros, meaning "occupying a cardinal point, situated on a centre",  from Epi "on, upon, at", and Kentron meaning "centre".The epicenter is directly above the earthquake's focus (hypocenter). In the case of earthquakes, the epicenter is directly above the point where the fault begins to rupture, and in most cases, it is the area of greatest damage. However, in larger events, the length of the fault rupture is much longer, and damage can be spread across the rupture zone. For example, in the magnitude 7.9, 2002 Denali earthquake in Alaska, the epicenter was at the western end of the rupture, but the greatest damage occurred about 330 km away at the eastern end of the rupture zone.

What is a Magnitude (Richter Magnitude scale) ?
The expression Magnitude Scale refers to a number of ways to assign a single number to quantify the  energy released in an earthquake.

Earthquakes are also classified in categories ranging from minor to great, depending on their magnitude.

What is an Intensity ( Mercalli intensity scale) ?
The Intensity scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake.The scale quantifies the effects of an earthquake on the Earth's surface, humans, objects of nature, and man-made structures on a scale from I (not felt) to XII (total destruction). Values depend upon the distance to the earthquake, with the highest intensities being around the epicentral area. Data gathered from people who have experienced the quake are used to determine an intensity value for their location.

Philippine earthquakes
The Philippines sits on several microplates between two convergent plates, the Philippine Plate and the Eurasian Plate. Tectonic activity in the country includes both earthquakes and volcanic eruptions. Because of subduction of the Eurasian Plate to the west, volcanic activity occurs along the Manila Trench and the Sulu Trench, often with powerful caliber. 13 percent of recorded eruptions in the Philippines have been deadly, as the country is responsible for the world's most deaths in volcanic eruptions. Seismicity as well has been powerful in the last 50 years, more than half of the country's major earthquakes have reached magnitude 7.0 or greater. The earliest known major shock was in 1976, killing some 8,000 people. 

 Luzon earthquake in 1645
The 1645 Luzon earthquake was one of the most destructive earthquakes to hit the Philippines. It occurred on a Monday, November 30, 1645 at about 08:00 PM local time on Luzon Island in the northern part of the country. The island was struck by a 7.5 Ms (surface wave magnitude) tremor produced by the San Manuel and Gabaldon Faults (Nueva Ecija) in the central section of the island. Aftershocks continued a few days after the quake then on December 4, 1645, a strong earthquake allegedly equal or stronger than the November 30 shaking hit the same area, causing further death and destruction. Its meizoseismal area was not less than 490 kilometres (300 mi) from north to south, that is, from the southern coast of Batangas and Quezon provinces to Cagayan in the northeasternmost part of the island. On the western coast, it seems to have been of less intensity; at least the chronicles of the time are silent about its effects in these parts. They dealt very much with the destruction caused in Manila and neighboring provinces to the south, east, and north, the tremendous effects produced in the eastern part of the Central Cordillera Mountains, and as far north as in Lal-Lo in the Cagayan Valley where large fissures opened in the earth and many large landslides occurred in the hills.
In Manila, damage was entirely severe almost all the city laid in ruins. It ruined the Manila Cathedral and other churches in the capital, public buildings and residential villas. An estimated number of 600 Spanish people were killed, and about 3,000 Spanish were injured. Only the Spaniards, who perished during the earthquake, were counted by the ruling Spanish government, while other persons were disregarded.

Luzon earthquakes in1880
The earthquakes of July 1880 in Luzon, the largest island of the Philippines, was one of the most destructive tremors on record in the history of our country. The shocks continued, with greater or less interruption, from the 14th to the 25th of the month, highlighted by three violent shaking events, which destroyed churches and other buildings, producing loss of life. Coinciding with the tectonic activity was an increased in volcanic activity in Taal Volcano in southwestern Luzon.
The Luzon provinces of Manila, Cavite, Bulacan, Laguna, Pampanga, and Nueva Ecija, were the chief victims from the terrible convulsions with Manila and Laguna receiving the most damages. In many places, buildings were converted into shapeless heaps of ruins, and the materials of their prosperity buried beneath the rubbish.

The vibrations began during the months of April and May, in the northern provinces of Luzon. The center of oscillation, as indicated by the directions registered at Manila, appears to coincide with a volcano, which has been long extinct, situated between Lepanto (now part of Kalinga) and Abra provinces, in the Central Cordillera of Luzon, in latitude 16° 22' N and longitude 127° E, according to the Spanish Observatory of San Fernando. At first the movements were weak and little frequent, but in the month of June they became quite intense, and extended from north to south over a large zone. This direction never changed; and the few discordances recorded appear to have been a result of haste or want of care in the method of taking the observations, exactness being hardly attainable without special instruments for the purpose. Taal Volcano was observed to start showing increase in activity from the 8th of June and sometimes at night the crater is covered with glare. Early in July some vibrations were felt, but from the 5th to the 14th none were recorded at Manila or any point on the island. On the July 14 at 12:53 p.m., as a storm from the northeast of Luzon was threatening as indicated by an extraordinary fall of the barometer, the first shock occurred. After this first tremor, there were two more shocks at the end of an hour and a half. On the 15th and 16th no perceptible shocks occurred; and on the 17th, only two small shocks.

Strange phenomenon in Cavite
On the occasion of the earthquake, the people in Cavite across the bay saw Manila enveloped in a dense cloud of dust, and thought that Manila was completely destroyed. A very interesting phenomenon was also observed in Cavite. During the intensity of the earthquake, in the anchorage of Cavite, columns of black mud were seen to burst up, with a strong smell of sulphur. The very interesting phenomenon was also observed in Manila a few days previous to the destructive earthquake of 1863, in front of the Colgante suspension bridge on Pasig River. A column of blackish water was seen to burst up, which attracted the attention of the people. In 1869, the same phenomenon occurred in Manila, then also previous to an earthquake.

Casiguran earthquake in 1968
The Casiguran earthquake occurred on August 2, 1968 at a magnitude of 7.3 on the Richter scale. The earthquake's epicenter was located in Casiguran, Quezon (now part of Aurora province). This was deemed the most destructive earthquake in the Philippines prior to the 1990 Luzon earthquake, and generated a tsunami that reached as far as Japan.

The city of Manila was the hardest hit with 268 people were killed and 261 more were injured. Many structures that suffered severe damage were built near the mouth of the Pasig River on huge alluvial deposits. A number of buildings were damaged beyond repair while others only suffered cosmetic damage. Two hundred and sixty people died during the collapse of the 6-story Ruby Tower, located in the district of Binondo. The entire building, save for a portion of the first and second floors at its northern end, was destroyed. Allegations of poor design and construction, as well as use of low-quality building materials, arose. In the District of Santa Ana, one person was injured by debris from a damaged apartment building. Two more people from Aurora sub province and Pampanga died as a direct result of the quake. Around the town of Casiguran, there were several reports of landslides, the most destructive one at Casiguran Bay.

Moro Gulf earthquake in 1976
The 1976 Moro Gulf earthquake and tsunami took place on August 16, 1976, near the islands of Mindanao and Sulu, in the Philippines. Its magnitude was calculated as being as high as 8.0 on the moment magnitude scale. The epicenter was in the Celebes Sea between the islands of Mindanao and Borneo. The Pacific Tsunami Warning Center's preliminary magnitude was given as 8.0 on the Richter scale and as 7.9 by other sources. There were many aftershocks following the main earthquake. A major aftershock on August 17  had a magnitude of 6.8. It was proceeded by at least fifteen smaller aftershocks. According to reports, the earthquake was recorded around 16:10.

The initial earthquake was widespread and was felt as far as the central Philippine islands of the Visayas. A massive tsunami devastated 700 kilometers of coastline bordering the Moro Gulf in the North Celebes Sea, resulting in destruction and death in the coastal communities of the Sulu Archipelago and southern Mindanao, including Zamboanga City and Pagadian City. At least 5,000 people died during the earthquake and tsunami, with thousands more remaining missing. Some reports say that as many as 8,000 people lost their lives in total, with ninety percent of all deaths the result of the following tsunami.
Initially over 8,000 people were officially counted as killed or missing, 10,000 injured, and 90,000 homeless, making the 1976 Moro Earthquake and Tsunami one of the most devastating disasters in the history of the Philippine Islands.After the initial earthquake the people were unaware of the need to move to higher ground; when the tsunami hit it sucked most of the victims out to sea. Based on the investigation on the affected region it was confirmed that the waves reached up to 4.0 to 5.0 meters (14-15 feet) when they hit the areas. There were reports of weak tsunami activity as far as Japan, as well as Indonesian Hydrographic Office reports of unusual wave activity affecting the islands of Sulawesi (Celebes Island) and Borneo.

Luzon earthquake in 1990
The Luzon earthquake occurred on Monday, July 16, 1990, at 4:26 PM local time in the Philippines. The densely populated island of Luzon was struck by an earthquake with a 7.8 Ms (surface-wave magnitude). The earthquake produced a 125 km-long ground rupture that stretched from Dingalan, Aurora to Cuyapo, Nueva Ecija as a result of strike-slip movements along the Philippine Fault and the Digdig Fault within the Philippine Fault System. The earthquake epicenter was placed at 15° 42' N and 121° 7' E near the town of Rizal, Nueva Ecija, northeast of Cabanatuan City.
An estimated 1,621 people were killed in the earthquake, most of the fatalities located in Central Luzon and the Cordillera region

The earthquake caused damage within an area of about 20,000 square kilometers, stretching from the mountains of the Cordillera Administrative Region and through the Central Luzon region. The earthquake was strongly felt in Metropolitan Manila, Destroying many buildings and leading to panic and stampedes and ultimately three deaths in the National Capital Region,one of the lowest fatalities recorded in the wake of the tremor. The Southern Tagalog (nowadays Regions 4A and 4B) and Bicol Regions also felt the quake, but with low casualty figures.

Mindoro earthquake in 1994
The earthquake occurred on November 15, 1994 at 03:15 local time  near Mindoro. It had a magnitude of  7.1.  78 people were reported dead. 7566 houses were damaged. There were landslides in the Verde Island. The epicenter of this earthquake was located in the Verde Island Passage, a strait separating Luzon and Mindoro.  The earthquake generated a tsunami, which affected Mindoro, the Verde Island, the Baco Islands, and Luzon. Some concrete structures also suffered moderate damage in the tsunami. In Baco Islands, the vertical run-up reached 8.5 m. The tsunami was also recorded in Lobo. The tsunami was larger than expected considering the magnitude of the earthquake.

Mindanao earthquake  in 2002
The 2002 Mindanao earthquake struck the Philippines on March 5, 2002. The sixth most powerful earthquake of the year, it registered a magnitude of 7.5 and was a megathrust earthquake. It originated near the Cotabato Trench, a zone of deformation situated between the Philippine Sea Plate and the Sunda Plate. The entire country is characterized by a high level of volcanic and seismic activity.
The earthquake was responsible for 15 deaths and roughly 100 injuries. Up to 800 buildings were damaged as a result, many from a flood generated by landslides and falling debris. A tsunami followed the earthquake.The epicenter of the earthquake was located near the Cotobato Trench. The magnitude of this megathrust earthquake was 7.5, the sixth strongest of the year. It occurred in a zone of geologic deformation along the Sunda and Philippine Sea Plates, which converge at a rate of 6 centimeters (2 in) each year.

 Philippine Sea Plate and the Sunda Plate. 
Mindanao earthquakes in 2010
The 2010 Mindanao earthquakes were a series of powerful earthquakes that occurred in the Southern Philippines in the Moro Gulf. There were no reports of damage or casualties as the shocks are deep-focus earthquakes occurring far too deep over 500 kilometres (310 mi) to pose any serious threat.

The southern part of the Philippines lies above the complex collisional zone between the Philippine Sea Plate and the Sunda Plate. The convergence between these two plates of between 6–11 cm per year is accommodated by a series of smaller plates. One of these, the Molucca Sea Plate, is currently being subducted beneath both the Philippine Sea Plate and the Sangihe Microplate, causing it to have an inverted U-shape seismic zone. The earthquakes were caused by the continuing distortion of the Molucca Sea Plate. The initial M7.3 event is the foreshock of the M7.6 while the M7.4 is an aftershock of the M7.6.
Areas affected
These earthquakes occurred in Moro Gulf, off the island of Mindanao. The Mw 7.6 earthquake were felt in Philippines, Taiwan, and Malaysia. The Mw 7.4 earthquake were felt in Philippines, Brunei, Malaysia, and Indonesia.

Visayas earthquake in 2012
A magnitude 6.7 (Mw) undersea blind thrust earthquake occurred off the coast of Negros Oriental, Philippines, on Monday, February 6, 2012 at 11:49 PST.  The epicenter approximately 72 kilometres (45 mi) north of Dumaguete, Negros Oriental. According to the PHIVOLCS Earthquake Intensity Scale (PEIS) were VII in Dumaguete and V (PEIS) in Cebu. The earthquake was felt as far as Mindanao in the provinces of Misamis and Lanao and as far as Iligan.  In Cebu, the earthquake was the strongest so far of 2012. The strongest earthquake to hit Negros happened in 1948, but did not cause massive damage.According to PHIVOLCS, the earthquake was caused by movement on a previously undiscovered fault. However, according to an Environmental Sciences professor, this fault was already known to private geologists hired by the Negros Occidental government to create a land use map for the province.
The Philippine Institute of Volcanology and Seismology (PHIVOLCS) gave a level two tsunami alert, indicating that the public should be on watch for "unusual waves", but did not call for any evacuation. Despite this, in Cebu City, panic ensued and many residents fled towards higher ground due to rumors that a tsunami had hit the coastal villages of Ermita, Mambaling and Pasil. Residents of Dumaguete also scrambled to the mountain town of Valencia because of the scare. These rumors were later confirmed to be false. PHIVOLCS announced the tsunami alert at 14:30 PST.
The degree and extent of damage caused by the earthquake were significant, with most of the damage sustained during the initial earthquake. The hardest hit were the towns of Tayasan, Jimalalud, La Libertad, and the city of Guihulngan, in Negros Oriental. Several houses and buildings collapsed, while others sustained damages. The earthquake also triggered numerous landslides which buried houses and people. Reported places where landslides occurred are Barangay Solongon, La Libertad and Planas, Guihulngan.

Philippine Earthquakes in History

  • An intensity VI quake struck Manila on June 25, 1599. The quake had damaged many private buildings and the city and ruined the roof of Sto. Domingo Church.
  • An intensity VIII quake struck Manila on January 2, 1600.
  • A quake struck Manila on January 16, 1601. Earthquake duration lasted about 7 minutes, and aftershocks were experienced the whole year.
  • An intensity VII quake struck Dulag Island and Palo Island, Leyte in December 3, 1608.
  • An intensity IX quake struck Manila on November 1610. It was a terrible quake that progressed from east to west.
  • An intensity IX quake struck Panay Island on 1620. A great casualties numbered in Capiz and Iloilo provinces. The earthquake changed the course of Aklan River and damaged stone churches and facades in Passi, Iloilo.
  • An intensity X quake struck Northern Luzon on 1627. Convulsions were experienced along Cagayan and Ilocos Norte provinces, Bontoc, Lepanto and central Cordillera Central. Other sources claimed that Caraballo Mountains somewhat subsided.
  • An intensity IX quake struck Albay and Camarines[1] on 1628. The quake caused avalanche of ashes, lapilli, water and sand that swept away Albay and Camarines towns.
  • An intensity IX quake struck Illana Bay, Western Mindanao on December 21, 1636. Landslides reported along Illana Bay, Sibuguey Bay and Point Flechas.
  • An intensity X quake struck Northern Luzon on January 4, 1641. The quake occurred after the 1641 eruption of Parker Volcano. Landslides and mudflow destroyed villages in Ilocos provinces, Cagayan and Cordillera Central.
  • A magnitude 7.5 quake struck Luzon on November 30, 1645. It was dubbed as the "most terrible earthquake" in the annals of the Philippines. It had greatly damaged ten newly-constructed cathedrals in Manila, residential villas and buildings in the city and nearby provinces. Provinces in the north reported several alteration of the ground, disappearances of small villages, changes in the river course, sand eruptions, etc. Small tsunamis were reported in southern Luzon. 600 were reported dead, and at least 3,000 were injured.
  • An intensity VIII quake struck Luzon on December 5, 1645. It was a major aftershock of the November 30, 1645 Luzon earthquake, and it had further destroyed remaining buildings in Manila and nearby towns. Aftershocks ceased around March 1646.
  • An intensity IX quake struck Southern Luzon on 1648. It was a very violent earthquake that wrecked many buildings.
  • An intensity VI quake struck Manila on May 1, 1653.
  • An intensity IX quake struck Southern Luzon on August 20, 1658. It was comparable to the 1645 Luzon earthquake, but had caused less damages on building and was less proximity from the epicenter. It had destroyed the Monastery of Santa Clara, several monasteries of the Dominicans and Recollects, Jesuit College and episcopal palaces.
  • An intensity VIII struck Manila on June 19, 1665. Only a Jesuit church experienced great damage. 19 were reported dead.
  • An intensity VIII struck Isla Verde Passage on February 1675. The quake destroyed many buildings in northern Oriental Mindoro and southern Batangas provinces. This led to occurrences of landslides, opening of ground fissures and subsidence of beaches along Mindoro coast.
  • An intensity VII struck Manila on August 24, 1683.

  • An intensity VII struck Lake Bombon (now known as Taal Lake) on September 24, 1716. It was connected with the eruption of Taal volcano; the constant volcanic activity in the area of Taal caused seismic movements.
  • An intensity IX struck Tayabas (now known as Quezon) on 1730. It had ruined the churches and convent in Mauban and several other churches in the province of Tayabas and Laguna.

  • An intensity X struck Luzon on July 14–24, 1880.The quake caused severe damage to these major cities in Luzon, most significantly in Manila where a lot of buildings collapsed. Number of casualties are unknown.
  • A quake struck Lucban, Quezon on October 26, 1884. It destroyed churches in Lucban town in Quezon province and Cavinti town in Laguna province.

  • A magnitude 7.5 quake struck Northeastern Mindanao on July 11, 1912. Damage and high intensity were experienced by towns of La Paz, Bunauan, Veruela and Talacogon in the Agusan Valley area where intense ground shaking, liquefaction, widespread landslides and river/lake seiches occurred.
  • An intensity VII earthquake struck Luzon, mainly Isabela on December 29, 1949. Starting at 11:05 a.m., it lasted for 2 and a half minutes. The damage was moderately destructive, causing landslides and sea waves capsizing boats. It also caused fissures that spit out black water. The intensity ranged from IV to VII throughout Luzon.
  • A magnitude of 7.3 quake struck Casiguran, Aurora on August 2, 1968 at the depth of approximately 31km. It was considered the most severe and destructive earthquake experienced in the Philippines during the last 20 years. 270 people were reported dead and 261 were injured.
  • A magnitude 7.0 quake struck Ragay Gulf on March 17, 1973. Calauag, Quezon was the worst hit, as the quake caused 98 houses totally destroyed, and 270 more were partially damaged.
  • A magnitude 7.9 quake struck Mindanao on August 16, 1976. The quake caused a devastating tsunami that had hit the 700 km coastline of the island of Mindanao bordering Moro Gulf in the North Celebes Sea. An estimated 5,000 - 8,000 people died. The major cause of the great number of casualties during the event could be attributed to the fact that the quake happened just after midnight when most people were sleeping; and a great tsunami was spawned, struck the coasts from different directions and caught the people unaware.
  • A magnitude 6.5 quake struck Laoag on August 17, 1983 at a depth of 42km. The quake has caused death of 16 people and injured 47 persons.
  • A magnitude 6.8 quake struck Bohol on February 08, 1990. Six fatalities were reported and more than 200 were injured in the event. About 46,000 people were displaced by the event and at least 7,000 among them were rendered homeless. Estimated damage to properties is amounting to 154 million pesos.
  • A magnitude 7.1 quake struck Panay Island on June 14, 1990 at a depth of 15km. 7 persons perished and 31 others were injured.
  • A magnitude 7.8 quake struck Luzon on July 16, 1990. It caused severe damage to major cities in Luzon: Dagupan City (soil liquefaction), Baguio City, and Cabanatuan City; Hyatt Terraces Baguio collapsed. 1,621 were reported dead. Damage to buildings, infrastructures, and properties amounted to at least P 10 Billion, a part of which was caused by ground rupturing. However, some houses within 1-2 m on either side of the ground rupture survived owing to their light-weight construction while those built of reinforced concrete within this zone suffered partial damage. Damages beyond 2m depended mainly on the structural integrity of the building and effects of local topography and ground conditions.
  • A magnitude 7.1 quake struck Mindoro on November 15, 1994 at depth of 15km. The quake caused a tsunami killed 41 persons and destroyed 1530 houses.
  • A magnitude 5.6 quake struck Bohol on May 27, 1996 at a depth of 4km. The earthquake did not cause major damages to properties. Damages were confined to poorly built structures and/or old wooden, masonry, limestone walls of houses and buildings, generally due to ground shaking.
  • A magnitude of 5.1 struck Bayugan, Agusan del Sur on June 7 and 9, 1999. The towns of Bayugan and Talacogon were the most devastated.

  • A magnitude of 7.5 quake struck Mindanao on January 1, 2001 at a depth of 33km.
  • A magnitude of 7.5 quake struck Central and Southern Mindanao on March 5, 2002 at a depth of 31km.[17] At least 15 people were killed, 100 injured and 800 buildings were damaged or destroyed.
  • A magnitude of 6.1 quake struck Sultan Kudarat on March 6, 2002. Office of Civil Defense (OCD) records show that 8 people had died and 41 were injured due to the earthquake. It affected 7,684 families in the provinces of Sultan Kudarat, Sarangani, North Cotabato and South Cotabato including four cities and 17 municipalities.
  • A magnitude of 6.2 quake struck Masbate on February 15, 2003 at a depth of 22km. The quake damaged major infrastructures in Masbate.
  • A magnitude of 6.5 quake struck Samar on November 18, 2003. 1 person was reported dead.
  • A magnitude of 6.5 quake struck Mindoro on October 8, 2004.
  • A magnitude of 6.6 quake struck Moro Gulf on October 4, 2009.
  • A series of quakes with the main quake's magnitude of 7.3 struck Moro Gulf on July 23–24, 2010.
  • A magnitude of 6.4 quake struck Ilocos Region on March 20, 2011.
  • A magnitude of 5.2 quake struck Valencia City, Bukidnon on November 8, 2011 at a depth of 1km. 39 people were injured, and several establishments were damaged.
  • A magnitude of 6.9 quake struck Negros, the rest of Central Visayas, and some parts of Mindanao on February 6, 2012 at a depth of 20km. The quake killed people, caused major damage on infrastructures, and buildings. A tsunami alert level 2 was raised due to the quake. The quake also caused a landslide, burying a barangay. More than a thousand of aftershocks were recorded by PHIVOLCS within 2 days since the quake occurred. According to National Disaster Risk Reduction and Management Council, as of February 18, 2012, the death toll have risen to 51 with 62 people still missing, and injuring 112 people. Most deaths came from the city of Guihulngan and La Libertad where landslides occurred. 63, 697 from provinces in Region VII were affected by the quake. 15, 483 houses were partially or totally damaged, and a total of P383 million cost of damages to buildings, roads and bridges, and other infrastructures were recorded.
  • A magnitude of 5.9 quake struck Surigao City on March 16, 2012. Many were injured in the city for that certain day was the grand opening of Gaisano Capital Surigao. An estimated 6,000 people were in Gaisano when the earthquake happened. The earthquake caused a stampede which injured people.

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