The strongest tremor by far recorded in Davao region was on April 14, 1924, when Mati City, Davao Oriental, where a 320-km Surigao–Mati fault line passes, was shaken by a monstrous 8.3-magnitude earthquake. Had the same quake happened today, the devastation would have been overwhelming. Roughly 500 inhabitants died in the calamity.
The tremor, with tectonic origin and was the strongest quakes ever to hit the country, had an epicentre that was 15-km deep. It was stronger than the 8.0-magnitude tremor that struck Davao Gulf, Mindanao, on August 17, 1976, which generated a tsunami that claimed the lives of over 8,000 people, injured around 10,000, and left homeless close to 100,000.
An earthquake is ”a sudden and violent shaking of the ground, sometimes causing great destruction, as a result of movements within the earth’s crust or volcanic action” while magnitude is “a number that characterizes the relative size of an earthquake.”
Thirty-one years earlier, Monkayo, a town under Compostela Valley Province, was visited also by a powerful 7.2-magnitude temblor, leaving in its wake massive landslides, realignment of riverways, and the destruction of farms. Death was reported but and a wide swath of agricultural and residential structures was flattened.
Jesuit priest Fr. Saturnino Urios recounted another tremor on June 21, 1893, while he was in Jativa (now a sitio of Haguimitan, Monkayo, Compostela Valley), saying a strong quake “unmistakably felt in Davao, threw St. Peter to the floor—the status above the main altar–and cracked a few tabiques, also altered the forest, eroding a few mountain peaks. I myself saw them, with their trees and everything in the ravines.”
(Tabiques are walls of wooden laths woven together and strengthened on the lower portion with lime or cement.)
In missionary chronicles, several other accounts of earthquake occurrences are documented.
In September 1879, Fr. Quirico More, S.J., was in Tuban, Santa Cruz, Davao del Sur, when “a more than ordinary earthquake” took place. On October 6, 1889, Fr. Mateo Gisbert, S.J., reported of “a strong earthquake” that happened at 11:00 in the morning: “The image of the saint fell from the altar, the bell rang, etc. Personal tragedy, none, in God’s mercy.”
Fr. Gisbert also reported that on May 1 and 2, 1891, two weak quakes hit Malalag, Davao del Sur, at noontime. These were followed two days later with “a strong one” that took place at 6:45 in the evening, and another “long, rotatory” tremor at 8:30 that night.
Two tremors struck Sigaboy (now Gov. Generoso, Davao Oriental) on February 10-11, 16 and 22, 1894. Fr. Juan B. Llopart, S.J., was an eyewitness to these twin events:
“A frightful earthquake occurred at 1:00 in the morning of February 10: a tremor, then a north-south oscillation lasting more than a minute, giving us a good shock. The house shook, everything came falling down. The frightful sound, the violent shaking mad one feel as though he was riding a carriage on rocky ground. There followed all day a series of tremors I the same direction, less intense that the first, and briefer.
“Tremors occurred on February 11. At 9:45 at night, there was a strong quake. Then tremors continued every day with less frequency. On the 16th, at 12:00 noon, a strong east-west tremor. The tremors continued until the 22nd. Then they occurred only every other day or so, until the 4th of this month [March] when the last tremor was felt.”
In the last five years (2013-17), the most powerful quake to hit the region was 7.2 in magnitude and it struck Davao Occidental on April 29, 2017. Fortunately, the origin of the tremor, tectonic in origin with a depth of 57 km, did not result in extensive damage but alerted the seismologists to a possibility of raising a tsunami warning.
This was preceded two weeks earlier by a 6.0-magnitude quake with Davao City as epicenter. On July 14, 2014, Davao Occidental was shaken by a 6.1-magnitude tremor, and Davao Oriental, on September 24, 2016, by a 6.5-magnitude temblor.
Since 2013, two over 5.0-magnitude quakes hit Davao region. On December 4, 2013, Davao Oriental was struck by a 5.7-magnitude shaking while Davao Occidental, on October 23, 2014 was hit by a 5.1-magnitude quake and on May 9, 2014, by a 5.7-marnitude tremor.
Another 5.0-magnitude tremor hit Davao Occidental on January 13, 2014, while two of the more powerful quakes to hit the region, a 4.8 and a 4.6, struck in 2017 Davao Oriental and Davao City, respectively. A ‘killer quake’ is expected to hit Davao City within the next few years.
According to the Davao Seismic Station, based in the Philippine Science High School in Mintal, Davao City, has two active fault lines in Ma-a and New Carmen, Tugbok, Davao City.
While there are no earthquake-generating fault lines in the region, Philvocs made it clear there is the Philippine Fault zone in Mati City and the Mindanao fault in Compostela Valley.
In recent years, following the disastrous effects of super typhoons and very strong tremors, the idea to organize a separate department that addresses issues on calamities gained currency.
Such idea, if enacted, will integrate agencies such as Philippine Volcanology and Seismology (PHIVOLCS), Office of Civil Defense (OCD), National Disaster Risk Reduction and Management Council (NDRRMC), and Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) under one roof.